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THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS 1/2016 Foot Pressure Measurements Basic Knowledge For Pedorthists Establishing a Global Priority Assistive Products List International Cooperation Allows Treatment Official organ of the “International Association for Orthopaedic Footwear” (IVO).

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Page 1: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

THE INTERNATIONAL JOURNAL

FOR FOOT ORTHOTICS

1/2016

Foot Pressure MeasurementsBasic Knowledge For Pedorthists

Establishing a Global Priority Assistive Products List

International Cooperation Allows Treatment

Official organ of the

“International Association for

Orthopaedic Footwear” (IVO).

Page 2: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

TThhee OOrrtthhooffiitt MMeeaassuurriinngg CCeenntteerr

TThhee OOrrtthheemmaa MMiilllliinngg CCeenntteerr

Ask for more information about prices and franchise concept:

ORTHEMA Group Fon: +41 41 798 04 34 Email: [email protected] CH – 6343 Switzerland Fax: +41 41 798 04 35 Web: www.orthema.com

3.–6. May 2016 in Leipzig

Visit us:

Hall 1 • Booth G42

Page 3: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

3foot & shoe 1/2016

When treating foot problems and foot deformities physicians often have to face the

question if a surgical intervention or a conservative treatment with orthopedic

app liances is preferable. Many aspects can play a role when

deciding in favor or against a therapy. Ideally the participating

physicians and the patient are familiar with all therapy options

and the treat ment is chosen that serves the patient best.

Unfortunately this ideal case only rarely occurs. Also in

countries where professions related to pedorthics and prosthetics

and orthotics have been established for a long time the treating

physicians often lack the knowledge about the orthopedic

appliances available today that can avoid for example surgeries

which often involve a risk for the patient.

In many countries not only the physicians lack the knowledge,

but also there are not enough trained specialists that are able to

produce these orthopedic appliances. This can be seen in our

case study from South Africa. The tree-years old Jaron is

completely healthy except for his midfoot and forefoot that have

not been completely formed osseously. This is why he is limited

in his movements and his condition would have led more than

likely to an overloading of the knee and hip joints if not treated.

As a treat ment the physicians recommended an amputation of the

lower leg.

Luckily his mother met Micha Oelsner, a German-trained pedor -

thist who has lived and worked in South Africa for many years.

In an interdisciplinary way and over many thousands of kilo -

meters, she developed with her partners a solution for Jaron

enabling him untroubled mobility considering also the family's

limited financial options and his future growth (see page 22).

This example shows that the development of pedorthics still has

many problems in numerous countries. There is not enough knowledge about

conservative treatments, often there is no health insurance for people less well-off

and there are not enough trained specialists. That is why many people have to deal

with limited mobility when they could have been helped with simple means.

A possibility to improve this situation is certainly the survey of the World Health

Organization. In order to enable world-wide access to conservative therapies and the

corresponding orthopedic appliances, the GATE-program of the WHO is currently

working on a Priority Assistive Products List. All treating people, patients and their

families should participate in this global survey so that the orthopedic appliances, so

important for mobility and health, are anchored in this list. You can participate in

this survey until 3 March 2016. On page 15 you can find further information.

Lack of Knowledge ImpairsMobility of Many People

E D I T O R I A L

Wolfgang Best

Chief editor

Kathrin Ernsting

Editor

Page 4: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

ResearchIn this study the bending and

torsional stress acting on the foot

in the Darco Relief Dual offloading

shoe were compared to occurring

stress in a competitor which was

already licensed.

4 foot & shoe 1/2016

C O N T E N T

10

9

16

30IMPRINT

THE INTERNATIONAL JOURNAL

FOR FOOT ORTHOTICS

www.foot-and-shoe.com/newsletter

foot & shoe(ISSN: 2193-9780) is the English edition of thejournal ORTHO PÄDIESCHUHTECHNIK. It is publishedtwice a year and distributed worldwide.

Publisher:C. Maurer Druck und Verlag GmbH & Co.Schubartstr. 21, 73312 Geislingen (Steige), GermanyFon: (+49) 07331/30708-0Fax: (+49) 07331/30708-69 and 30708-68Internet: www.maurer-fachmedien.dewww.foot-and-shoe.com

Executive Publisher:Carl Otto Maurer

Organ:Official organ of the “International Association forOrthopaedic Footware” (IVO).

Production:C. Maurer Druck und VerlagGmbH & Co. KG, Geislingen (Steige), Germany

Editorial Staff:Editor-in-chief: Wolfgang Best (be)(responsible for content)Fon: (+49) 07331/30708-10E-Mail: [email protected] Schmidt (tom)Fon: (+49) 07331/30708-11E-Mail: [email protected] Switala (sw)Fon: (+49) 07331/30708-12E-Mail: [email protected] Ernsting (ke)Fon: (+49) 07331/30708-13E-Mail: [email protected]

Translation:

Sylvia Best

Layout: C. MaurerPrinted articles and pictures pass on to the right ofpublication and dissemination of the publisher withinthe framework of the legal requirements. Revisionsand abbreviations are in the discretion of the pub -lisher. Reprints, photomechanical reproductions ortranslations only if especially authorized by the pub -lisher. The publisher and the editorial team do not take responsibility for unsolicited articles.

Advertising:Sibylle Lutz, Editorial OfficeBlumenhagenstr. 11, 30167 Hannover, GermanyFon: (+49) 0511/35319830Fax: (+49) 0511/35319840E-Mail: [email protected]

Advertising Administration:Gabriele Meyer-Dahms,Fon: (+49) 07331/30708-20,E-Mail: [email protected] Rate List No. 4, valid from 1 January 2014There is no claim for subsequent delivery or compensation if the magazine is not published due to force majeure.

Subscription Support:Maurer Verlag Aboservice,Schubartstraße 21, 73312 Geislingen/Steige, GermanyFon: (+49) 0 73 31/30708-28Fax: (+49) 0 73 31/30708-69E-Mail: [email protected] Details: Kreissparkasse GöppingenIBAN DE14 6105 0000 0049 0557 48, BIC GOPSDE6GXXX

Foot Pressure MeasurementsThe aim of this article is to present the

main characteristics of measuring

technologies used for analysing the foot-

ground-contact, to differentiate the main

parameters measured by the mentioned

technologies, to discuss the settings of

optimal values for the defined parameters,

and finally to show two examples of

typical applications in the fields of

orthopedics and sports.

Etiology of Hallux ValgusAn understanding of how hallux valgus

develops is important for treating the

deformity. The functional analysis from

clinical practice shows how they affect

the biomechanics of the foot as well as gait

execution.

Diabetes-related AmputationsResearchers said double-digit decreases in

two of three types of common diabetes-

related amputation emphasize improvements

in care made in the last two decades.

Page 5: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

C O N T E N T

CONTENT

Editorial 3

Imprint/Index of Advertisers 3+4

About Terminology 6

Swiss Association with New Structure 8

Diabetes-related Amputations

Fall Significantly Since 1990s 9

Etiology of Hallux Valgus 10

Global Survey: WHO

Priority Assistive Products List (APL) 15

Basics of Foot Pressure Measurements 16

Treatment Possible

Through International Cooperation 22

Announcements of the Industry 26

Conferences and Congresses:

Upcomming Events 28

Talking with Iris Burtscheidt 29

SCIENCE

Analysis of Bending and Torsional Stress on the

Foot in Different Offloading Shoes

Original Research Report

by Nora Dawin et al 30

INDEX OF ADVERTISERS

Beil 9

B-O-S-S 11

Brocksieper 17

C. Maurer

Fachmedien 27

Darco 5

Hardo 11

Messe Leipzig 23

Nora 21

Orthema 2

Renia 36

Schein 7

Spigron Spin 13

Insert note

We placed a self-promotion of C. Maurer Druck

und Verlag, 73312 Geislingen in this issue.

We ask for our readers attention.

Postoperative Care Trauma Care

Preventive Care

Every 15 seconds a DARCO product is prescribed

somewhere in the world. For over 30 years, DARCO has

provided the highest quality in foot care prod ucts.

DARCO distributes innovative products for foot surgery

worldwide. We set the standard for postoperative,

trauma, diabetic and wound care for the foot.

www.darco-europe.com

OTWorld 2016 in Leipzig!

Visit us in hall 1, stand B04.

DARCO – Focused on Foot and Ankle

Diabetic/Wound Care

Page 6: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

6 foot & shoe 1/2016

O R T H O PA E D I C S H O E S I N T E R N AT I O N A L

charge of the design, manufacture, fit,

and modification of foot appliances as

prescribed for relief of painful or dis-

abling conditions of the foot.

Now, the book has been translated in-

to English and targets readers in many

countries governed by thoroughly differ-

ent traditions. Whereas some countries

already have state-certified educational

programs, in many others, the orthotic

care of foot disorders is still in its baby

shoes. The qualifications and areas of

application are variously characterized.

Indeed, there is no standardized termi-

nology applicable to all countries. In

commissioning the translation of this

book, we obtained the advice of numer-

ous experts, while our translators under-

took extensive research to identify the

terms commonly used in other countries

to describe the products, tools and pro-

cedures in order to establish the most

appropriate translation of that term.

Among others, we have applied interna-

tional standards that set down the ter-

minology on specific orthopedic appli-

ances and pedorthic devices.

Nevertheless, the authors couldn't re-

sist adding a chapter on terminology to

explain to the reader the etymology of

the main terms used and the variety of

possible synonyms and internationally

common translations. Even when a term

may seem to have an equivalent in the

other language, each country tends to

have its specific legislation and training

program governing the field. Thereby,

the term and the profession it denotes

have entirely different meanings in the

respective countries.

One prime example is the term

"podology". In most English-speaking

countries, the term is the equivalent of

"podiatry" or "chiropody", a specialized

field of medicine dealing with the study

and care of the foot. However, the Ger-

man term 'Podologie" cannot be trans -

lated "literally". This term is not to be

confused with the practice of podiatry or

chiropody. In Germany, the profession

"Podologist" is protected by law. The

statutes differentiate between practi-

tioners in the field of professional foot

care with state-certified qualifications

and persons with minimal vocational

training or none at all who give pedi-

cures.

Foot orthoses In the vernacular, numerous terms are

used to describe the orthopedic appli-

ances designed to support, align, pre-

vent or correct deformities or to improve

the function of the foot, sometimes re-

ferred to as orthotic insoles, inlays, in-

soles, custom-made insoles, orthotics or

orthoses. In the textbook, we decided to

use the term "foot orthosis" because it

best reflects the function of the appli-

ance. A foot orthosis is prescribed to

correct the foot and support its physio-

logical kinematics and kinetics by means

of specially incorporated features. This

definition is in compliance with ISO

13404:2007(E). In the case of foot or-

thoses, it is important to distinguish be-

tween custom-made and prefabricated

foot orthoses.

Individual foot orthoses are not only

fabricated for the patients' feet, but for

their individual functional needs as pre-

scribed by the physician. Impressions of

the foot are taken, usually with plaster

casts, and the dimensions of the foot are

measured by hand or digital on a scan-

ner.

Prefabricated foot orthoses are sup-

plied in a variety of designs, each aimed

at fulfilling certain functional require-

ments. They are either modified for in-

sertion into the shoe or adapted to fit

the specific patient.

The term foot orthosis should not be

used to refer to any type of insertable

The technical terms of any profes-sion have rarely been fully stan-dardized. Different terms become

established, depending on the countryor even the occupational background.Even if there are binding definitionson terminology, for example based onagreements with the statutory healthinsurance companies, the common jar-gon is not rarely a colorful mixture ofconcepts describing the features andtechnical application of the productsbeing used. The parties involved most-ly know what is meant. However, whenit comes to writing a textbook on aspecialized subject, it is obviously im-portant to mention the vernacular, butprovide definitions that are standardi-zed and appropriate. This is particular-ly relevant when a textbook is beingtranslated. The translation should notonly be correct according to the dic-tionary. Rather, it also aims to use theterms and descriptons common in theprofessional vernacular of the book’starget readership. In the case of a book, that task

proves especially challenging. The text-

book entitled "Pedorthics" looks back on

a centuries-old tradition of a craft in

Central Europe called "orthopedic shoe

technology". Over the years, the manu-

facturing techniques and therapeutic

concepts have been brought up to the

state of the art. Nowadays, custom-made

orthotic footwear, foot orthoses, com-

pression stockings, special shoes and

sport orthoses for the foot, belong to

the range of services offered and prod-

ucts crafted by master pedorthists. They

acquire their knowledge and skills in a

three-year dual professional, workshop-

and classroom-based training program

which can be supplemented by an addi-

tional qualification to become a master

craftsman in pedorthics. The master or-

thopedic shoemaker is a practicioner in

How do you translate a reference book into English if many specialist

terms have not been defined clearly and many different terms are used

in the practice? This was the task the authors and translators of the

rtextbook "Pedorthics" had to face. In the following article the authors

explain how and why they chose certain terms and offer suggestions

for a more precise terminology.

About Terminology

Page 7: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

Pedorthics:

Foot disorders – foot orthoses – footwear

Prof. René Baumgartner, M.D.,

Michael Möller,

Dr. Hartmut Stinus

360 pages, 52 Chapters, more than 1 000 pictures and illustrations119 Euro ISBN 978-3-87517-050-4

The textbook “Pedorthics”

covers all of the aspects es-

sential to providing pedorthic

care of the foot using the

most modern techniques and

technologies – from the medical basics and the relevant

diseases up to and including the individual production of tools.

The objective of this book is to provide a comprehensive pre-

sentation of pedorthics as it exists today. Three experts have

teamed up for this: the Master pedorthist Michael Möller from

Münster and two orthopedic surgeons who have more than

just an academic interest in the field. One learned the trade

before turning to orthopedics, the other is proud to be an

honorary Master of the craft. Both aim to bring conservative

and operative orthopedics together under one roof. The help

of recognized specialists was enlisted for individual chapters.

All in an effort to not only inspire pedorthists, but other or-

thopedic specialists as well.

The first German edition of the book was so popular with

the inclined readership that only two years after publication,

the second revised edition was published. During the revision

process, authors and collaborators have done their best to

critically check and review the state of their knowledge and

pass it on in comprehensible form. The translation into Eng-

lish is based on this second edition.

This work's clear structure, more than 1 000 color illustra-

tions and comprehensive presentation make it an ideal com-

panion for training and daily practice.

The book takes a multidisciplinary approach: a compact

and competent presentation of diseases of the foot is aligned

with treatment strategies and the planning and implementa-

tion of tools such as foot orthoses, orthotic footwear and or-

thotic devices. Chapters on posture and movement analysis,

the basics of biomechanics, physiotherapy, orthopedic and

surgical operations as well as compression treatment round

off the spectrum of topics. An entire chapter is dedicated to

comprehensive treatment of the diabetic foot.

It is not merely practitioners and apprentices who will

find answers and assistance in providing patients with

pedorthic treatment in this book. Anyone involved in the

prescription of orthopedic aids or who deals with the prob-

lems associated with pedorthic foot care will appreciate the

book as an ideal reference. It provides all the essential infor-

mation on diseases, medical treatment strategies and pedor-

thic treatment in concentrated form.

PEDORTHICSFoot Disorders – Foot Orthoses – Footwear

René Baumgartner

Michael Möller

Hartmut Stinus

40° – 50°

Insole technology

Plastic materials

Padding materials

Reinforcing materials

Leather

Textiles

Metals

Cork

Special shoes for

people with diabetes

or rheumatism

Machines

for ortho paedic

technology

Measuring and

analysis systems

Orthotic-, Support-,

and Antivarus shoes

by

SCHEIN ORTHOPÄDIE SERVICE KG

Hildegardstr. 5 · 42897 Remscheid, Germany

Phone +49 2191 910-0 · Fax +49 2191 [email protected] · www.schein.de

O R T H O PA E D I C S H O E S I N T E R N AT I O N A L

Page 8: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

8 foot & shoe 1/2016

O R T H O PA E D I C S H O E S I N T E R N AT I O N A L

ready-to-wear shoe, normal shoe, ordi-

nary shoe. In the book, we refer to this

type of conventional shoe as "regular

shoes".

Likewise, a multitude of different

terms exist to describe prefabricated

shoes that serve an orthopedic function

or that allow modifications to be made

to the shoe or accept a custom-made

foot orthosis: Extra-depth-shoes, semi-

orthopedic-shoe, diabetic footwear,

medical footwear, therapeutic shoes.

Comfort shoes are defined as shoes that

have a last form that gives the foot

enough space, thereby designed to allow

the foot to exert its natural, physiologi-

cal function. These shoes often feature

individually modifiable soles and suffi-

cient room inside to accept a customized

foot orthosis.

In the book, the term "prefabricated

orthotic footwear" is used to describe

shoes developed to meet the needs of a

specific target group and featuring op-

tions for custom modification, whether

by making changes to the shoe or by in-

serting a customized foot orthosis. This

term describes our attitude towards the

function of these shoes, which by virtue

of their construction, by modifications

made to the shoe or through the custom-

made foot orthosis assume the function

of an orthesis.

As stated above, custom-fabricated

shoes are indicated when the foot is so

severely deformed that it does not fit

into a regular prefabricated shoe or the

foot's function is so severely impaired

that a regular shoe will not long achieve

the therapeutic objective set by the doc-

tor. As a rule, such shoes are prescribed

by a specialist in orthopedics. A cus-

tomized last is manufactured according

to the patient's foot dimensions and

needs and the shoe is fabricated around

the customized last.

Functional insertable orthotic devices

like reinforcements, stiffening, support-

ing devices, cushioning and footbeds

fabricated according to the individual re-

quirements prescribed by the doctor turn

a normal custom made shoe into an or-

thotic custom-made shoe. There are a

multitude of terms used to refer to these

shoes: custom-made orthopedic shoes,

orthopedic made-to-measure- shoes,

measurement-shoes, custom orthotic

footwear, bespoke shoes. In the book,

the term "custom orthotic footwear" is

used for this type of footwear. We are

aware that this term has not yet become

established as common vernacular. Nev-

ertheless, it is our opinion that the word

"orthotic footwear" best describes the

functionality of this pedorthic appliance.

It describes the fact that we are dealing

with a shoe that not only conforms to

the dimensions of the patient's foot

measurements, but also serves as a func-

tional orthosis, which gives the foot sta-

bility and positively influences the gait

characteristics and the loading of the

foot by means of the insertable orthotic

device inside the shoe.

Prof. René Baumgartner, Michael Möller,

Hartmut Stinus

sole (insole, insert, inlay, socket liner

etc.) unless it is designed to support the

foot in its function.

The term "foot orthotic" is also used

to describe a foot orthosis. Currently, de-

bates are ongoing about how best to de-

lineate these two terms from one an -

other. One proposal is to coin the term

"Foot Orthotics" not as a singular

footwear product or item worn on the

lower limb, but as a descriptive term en-

compassing the entire working area in-

volved in treating foot disorders by

means of foot orthoses, for example their

classification, their function, their fabri-

cation and their use.

Orthotic footwear Shoes are our companion on most of our

journeys. Most shoes are industrially

manufactured. The aim is to make them

to fit the largest general group of peo-

ple. However, they do not claim to offer

any solution to our personal foot prob-

lems. Meanwhile, a broad range of pre-

fabricated shoes is flooding the market

tailored to meet the demands of patients

with certain pathologies, or ones that

feature options to individually adapt the

shoes to the needs of a patient. If the

modifications to a prefabricated shoe are

not sufficient, single shoes can also be

custom made to meet the functional

needs of the patient. The English lan-

guage has many different terms to de-

scribe the industrially manufactured

shoe without any orthopedic function:

conventional shoe, ready-made shoe,

Swiss Association with New Structure

After a two-year long project peri-od, the Swiss association "Fuss& Schuh" ("Foot & Shoe") as

well as the two associations of pedort-hists and shoemakers have been orga-nized into one single association since1 January. The members of the asso-ciations agreed upon the consolidati-on without any negative votes on theoccasion of the extraordinary generalassemblies in fall 2015. With this ac-tion the forces of the three associati-ons that had been legally independentare joined. The association's name isnow only "Verband Fuss & Schuh"("Association Foot & Shoe"), comple-mented by the claim "Orthopä-dieschuhtechnik und Schuhservice

Schweiz" ("Pedorthics and shoe servi-ce Switzerland"). With an up-to-dateand dynamic logo the association gi-ves itself a new face. The logo is sup-posed to reflect the embedding withthe national skilled crafts and tradeand the importance of the educationsite Switzerland.The tasks of the previous associa-

tions of pedorthists and shoemakerswill now be carried out by the respec-tive groups within the association

"Fuss & Schuh" ("Foot & Shoe"). Forthe presentation in the public the pe-dorthists will additionally use theirprevious logo, which shall now serveas the label of the owner's profession-al qualification.The idea is that the association will

gain more efficiency through the sim-pler organizational structures. There isless overlapping in the panels and inthe administration and thus decisionscan be made faster and more directly.

Page 9: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

M E D I C I N E & T E C H N O L O G Y

2011 in the County of Funen, home to

about half a million people, from the

hospital administration system, Dan-

ish National Diabetes Register and

Statistics Denmark. During the 15-year

period, the researchers found a total of

2,832 amputations performed – 1,285

on patients with diabetes and 1,547

among those without diabetes.

Diabetes patients had eleven times

the risk of below-ankle amputations,

seven times the risk for from-ankle-to-

knee amputations, and four times the

risk of needing above-knee amputa-

tions, but the rate of each type of

amputation fell by 10 percent, 15 per-

cent, and 3 percent during the study

period, researchers reported.

"The reduction of amputations

among diabetics is encouraging. The

results presented here indicate that

multidisciplinary diabetic clinics

optimized for screening and treating

complications linked to diabetes are

beneficial," the researchers wrote. "It

is encouraging that the overall ampu-

tation rate is declining in most parts

of the world. However, amputation

rates in patients with diabetes remain

high compared to individuals without

diabetes posing a great challenge to

improve care."

First published on www.UPI.com

Improvement of diabetes treatment

has led to a significant decrease in

amputations related to the dis -

ease, according to a study of medical

records in Denmark.

Nerve and blood vessel damage are

among the long-term effects of the

disease, and often lead to poor circu-

lation in the lower limbs and feet. The

circulation can be so bad that hospi-

talization and amputation are neces-

sary. Better care of diabetes patients –

specifically improved drugs, and in-

spection and self-care of foot ulcers

related to the disease – has led to the

decrease in poorer conditions that

lead to amputation.

"The introduction of vascular

surgery and improved surgical tech-

niques cannot explain our findings,

since these procedures are applied

equally in individuals with and with-

out diabetes," researchers wrote in the

study, published in Diabetologia. "The

findings in individuals with diabetes

can therefore only be explained by im-

proved diabetes care, namely improved

metabolic control through drugs or

lifestyle, or changes in how care is de-

livered, including better screening –

we believe it to be both."

Researchers at Odense University

Hospital in Denmark analyzed health

records collected between 1996 and

Researchers said double-digit decreases in two of three types of common diabetes-

related amputation emphasize improvements in care made in the last two decades.

Diabetes-related amputationsfall significantly since 1990s

Better medications and improved self-monitoring of

diabetes ulcers has helped to decrease the number of

patients who require amputation.

(Photo: www.pixabay.com)

Orthopedic plastics by BEIL since 1962

phone +49 (0) 51 71 / 70 99 0www.BEIL--PEINE.de

orthopedic

plastics

BEIL

WE ARE

TO YOUR VISIT

LOOKING

FORWARD

Leipzig: 03. - 06. Mai 2016

Hall 1 Stand G 59

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10 foot & shoe 1/2016

M E D I C I N E & T E C H N O LO G Y

Is improper footwear the rootcause of the problem? There have been times when it waspresumed that, because of the gender-specific frequency of the occurrence ofbunions in the females of our species,fashion trends in shoes were respon -

sible for the development of halluxvalgus. High-heeled shoes with insuf-ficient heel support and a narrow, V-shaped toe box were considered to bethe significant causative factor in hal-lux valgus development. In addition,women often purchase this type of

It is striking that not only scien- tific journals but also textbooksdealing with the subject of hallux

valgus usually begin by explaining thepathoanatomy of hallux valgus defor-mities. These descriptions cover theenlarged intermetatarsal angle, themetatarsophalangeal angle, the size ofthe false exostosis, the altered articu-lar surface angle, subluxation of thesesamoid bones, rotational malpositio-ning of the hallux along with the al-ternating directions in which the ten-dons inserting into the hallux pull. At-tention is also focused on the extentof degeneration. No detail should beoverlooked when taking the patient'sstatus, which should be taken into ac-count during the later correction.

However, there is hardly ever men-tion of why hallux valgus occurs. Thisis not a question of an unusually pecu-liar entity. Indeed, knowing the etiol-ogy allows the therapeutic approachto be converted into a sustainabletreatment outcome. This article is notconcerned with the rare congenitalhallux valgus; therefore, the congeni-tal etiology will be disregarded here.

An understanding of how hallux valgus develops is important for treating the deformity.

From a biomechanical point of view, one key causal factor might be decisively related

to shortened calf muscles. The following functional analysis from clinical practice shows

how they affect the biomechanics of the foot as well as gait execution.

Etiology of Hallux Valgus

1–2 Many deformities are associated with shortened calf muscles, which can cause supination malpositioning of the forefoot towards the hind-

foot (right). The abduction of the forefoot can lead to incorrect loading of the big toe, manifested by a distinct pattern of callus formation (left).

3 Although the

wearer may force

her feet into her

elegantly tapered

pumps, it is rather

obvious this will

harm the foot in the

long run. But is this

really the major

cause of hallux

valgus?

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M E D I C I N E & T E C H N O LO G Y

4–9 Lateral view of the bare foot (top) and foot in the pump (bottom). A body weight of 60 kg corresponds to a weight force of 600 N when standing on one

foot. As the force parallelogram on the right shows, these 600 N are distributed along the bare foot such that 488 N are taken up by the heel and 112 N by the

metatarsal heads. When wearing her pumps fashioned with a heel lift of 4.5 centimeters, however, her heel must bear 280 N and her metatarsal heads 320 N.

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M E D I C I N E & T E C H N O LO G Y

metatarsal heads when she standsbarefooted.

When wearing her pumps with aheel lift of 4.5 centimeters, however,the weight force distribution changessuch that 280 N must be borne by theheel and 320 N by the metatarsalheads.

In addition, during each decelera-tion of the foot in the stance phase ofthe gait cycle, the foot has the ten-dency to slip forward on the inclinedplane of the high-heeled shoe, forcingthe toes into the V-shaped toe box.

This might explain the etiology ofhallux valgus. Yet in practice, despitethe fact that high heels are now wornless often, at least in Germany, the in-cidence of hallux valgus deformitieshas remained consistent. So what isthe crux of the matter?

Shortened calf musclesPediatric orthopedists have long known how significantly a pes equinuscomponent can affect forefoot posi -

tioning. Specialists who have dealtwith cerebral palsy have long beenaware of the concurrent incidence ofshortened calf muscles with hallux val-gus. Nevertheless, our focus of interestdoes not end with this detail.

Our own studies and observationsof pes planus have led to evidencethat shortening of the calf musclesoccurs in pes planus deformities with aregular frequency. The occurrence ofpes planus without shortened calfmuscles is practically nonexistent. Buthallux valgus regularly coincides withthis deformity as well.

Considering the biomechanics, thisseems quite plausible. Shortening ofthe calf muscles leads to a three-di-mensional deformation of the foot.Firstly, severe plantar flexion of thehindfoot causes the medial longitudi-nal arch to flatten. The talar headforces itself between the sustentacu-lum tali of the calcaneus and the nav-icular bone – the plantar calcaneonav-icular ligament widens. Secondly,

shoe in a size too small for their feet,which has a biomechanically damagingeffect on their big toe.

Thoughts such as these are logicaland closer inspection reveals observ-able changes in weight distributionand in the forces acting on the footand toes.

Figure 3 shows a dorsoplantar viewof the foot and the associated highheel from above. Hard to imagine, butthe foot does let itself be wedged intoa much narrower shoe. The distribu-tion of the acting (weight) forces ex-erted on the fore- and hindfoot duringstanding can be divided across a forceparallelogram. Figures 4 - 9 show theclinical macroscopic, radiographic anddiagrammatic views with and withoutthe heeled pointed-toe shoe.

When this young woman weighing60-kg stands on one foot, her bodyweight translates into a weight forceof approximately 600 Newton (N). Thisconverts into a distribution of 488 Nonto the heel and 112 N onto the

10–13 The Silfverskjöld test allows conclusions to be drawn on whether shortened calf muscles are the underlying cause of the deformi-

ty. The flexibility of the gastrosoleus muscle is tested with the knee flexed and the ankle in dorsal extension (left).

Next, the knee is slowly brought into the extended state (right), causing the gastrocnemius muscle to be stretched as well. If the dorsal

extension of the ankle decreases during this movement, it is an indication of a shortened gastrocnemius muscle.

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inflammation, immobilization in acast, a tumor or something else.

The response is always the same,producing greater tone in the musclesaffected by the functional unit. How-ever, because the more tonic and morephasic muscles in the musculoskeletalsystem react differently, specific mus-cular imbalance patterns develop.While more phasic muscles tend to be-come weaker in the case of dysfunc-tion, more tonic muscles tend toshorten. Of course, the division ofskeletal muscle into tonic versus pha-sic muscles is an oversimplification;the long evolution of us Homo sapienshas resulted in our muscles no longerbeing purely phasic or purely tonic,but always a mixture of both. Never-theless, this simplified view makessense because it can help us deduceand recognize imbalance patterns.

This fact can easily be verified forthe calf muscles with the help of theSilfverskjöld test (Fig. 10- 13). Duringexamination of the left leg, the exam-iner’s left hand encircles the patient'sfoot such that the ball of the thumbreduces the medial longitudinal archwhile finger and thumb place the heelin orthograde orientation and theforefoot rests on the examiner’s distalforearm. The examiner's right handguides the patient's knee. At 90-de-gree flexion of the knee joint, the an-kle joint's ability of for dorsal exten-sion is tested without the foot flatten-ing in the medial longitudinal arch orthe forefoot assuming an abductionposition. At a 90-degree flexion posi-tion of the knee, the gastrocnemiusmuscle is initially relaxed because of it

close vicinity to the origin (musclesattaching to the tibial and fibularcondyles) and insertion (calcanealtuberosity). First, the flexibility of thegastrosoleus muscle is tested. Next,the knee is slowly brought into full ex-tension, causing pre-tensioning of thegastrocnemius muscle due to the dis-tance from origin and insertion. Fre-quently, dorsal extension of the ankleis reduced.

Clinical observations made in asepa rate study by the author showedthat a coincidence of a shortenedgastro cnemius muscle was present in97% of hallux valgus deformities.

Impact on the biomechanics ofgait executionShortening of gastrocnemius musclechanges the biomechanics of gait exe-cution. In all cases, there is increasedloading on the forefoot, because theheel no longer has full mobility in theplantar direction, thereby preventingthe forefoot from deviating to the dor-sal during the propulsion phase of thegait cycle.

What happens after that dependson the individuality of the foot's skele-tal structure. If the "weak point" is inthe subtalar and/or Chopart joint, thefoot deviates into abduction and thepressure from the plantar medial sur-face causes the development of halluxvalgus.

If the foot is very stable within thesubtalar and Chopart joint, yet has a"weak point” in the Lisfranc joint line,pes transversoplanus may developwith hallux valgus developing as oneof the secondary sequelae.

there is simultaneous abduction of theforefoot in relation to the hindfootand, thirdly, an eversion movement ofthe entire foot which is more pro-nounced in the forefoot than in thehindfoot. For the hindfoot, this meansthat the heel is forced into a valgusposition – called the valgus foot or pesvalgus.

Because the eversion movement ofthe forefoot is greater than that of thehindfoot, this causes malalignment ofthe forefoot towards the hindfoot onsupination over the long term. GeorgHohmann illustrated this very impres-sively in his book “Fuß und Bein”[Foot and Leg]. Therefore, if the hind-foot is brought into its orthograde po-sition during manual examination, theforefoot will be in malalignment onsupination (Fig. 2).

The abduction of the forefoot caus-es incorrect loading of the hallux,which in turn no longer experiencesloading in the direction of plantarflexion / dorsal extension, but ratherpressure from plantar medial surface;this is usually identifiable by the pat-tern of callus formation (Fig. 1).

Identifying muscular imbalancesIt appears that the change in pre-ten-sioning of the calf muscles also altersthe biomechanics of the foot. As didProf. Buchmann, Travell and Simonsnoted that a failure of our joints is al-ways accompanied by a shift in the ba-lance of the surrounding muscles. Muscles cannot tell whether this dys-function is caused by a blunt impacttrauma, subluxation of the joint,

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The treatment of hallux valgus of-fers a broad enough scope to allow ad-ditional approaches to be applied.Whole publications are devoted to de-scriptions of individual methods fortreating specific types of hallux valgusdeformities. These treatments must always be based on the individual'spathology and can no longer be car-ried out according to “standard oper-ating procedures”.

In terms of shortened calf muscles,any successful therapy must take theminto account. The indication for a hal-lux valgus correction is never renderedin an emergency situation. That meansthat there is generally always time toapply a conservative approach. Phy -siotherapeutic interventions in theform of detonification of the calf mus-cles, stretching exercises, trigger pointtreatment, antagonist training and co-ordination exercises complemented byphysical therapy, such as the applica-tion of heat to "tense" muscles, all belong to the conservative standardtreatment regimen. Needless to say,physical therapy is essentially a guideto self-treatment and therefore onlymarginally burdens the limited budg -ets of private-practice physicians.

If appropriate, a technically well-crafted foot orthosis and/or shoemodi fication made by a pedorthistmay help improve the biomechanics ofthe foot to the extent that a less extensive surgical procedure is re-quired in the end. The possibility forinfluencing the outcome should be re-visited prior to each impendingsurgery.

References

References with the author

Dr. Ludwig Schwering has been the

medical head of the technical orthopa-

edics at the Mathias Spital in Rheine

from 1 September 2014. He is an ortho-

pedist and an orthopedic surgeon with

the additional denominations sports

medicine, chiropractic therapy, child-

ren's orthopaedics and special orthope-

dic surgery. He was the leading senior

physician and deputy chief physician of

the department for children's and sever-

ely disabled persons' orthopaedics of or-

thopaedics III at the Krankenhaus See-

park, Langen-Debstadt, as well as the

head of their occupational therapy from

1996 to 2000. From 2001 to 2004 he

worked as a senior physician within

children's orthopaedics at the Orthopä-

dische Klinik of the university hospital

Freiburg. From 2004 to 2012 he was

the medical director of the children's

and disabled persons' orthopaedics/

foot surgery of the department for or-

thopaedics and traumatology at the

university hospital Freiburg. From 2012

until 2014 he developed the depart-

ment of children's orthopaedics at the

American Hospital Dubai.

If the foot is quite stable in thisarea as well, the pressure is transferredonto the metatarsal heads producingthe extensor substitution phenomenon.During this reaction, the extensors are activated to "assist" the tibialisanterior muscle and facilitate betterdorsal extension. In relation to thefoot, the toes are also pulled intomaximum dorsal extension as part ofthe movement and the forces acting inthe retrograde direction induce a plantar pulling force to act on themetatarsal heads.

Another known etiology of halluxvalgus is the instability of the firstmetatarsocuneiform joint. Whetherthis is more primary or secondary,however, is unclear. In likelihood,both etiological mechanisms are pos-sible. Nevertheless, under all circum-stances, they must be considered inthe diagnosis of hallux valgus as wellas in its treatment. The same appliesto any insufficiency of the tibialis pos-terior muscle due to injury or degen -eration, as well as to all other imbal-ances arising from any number of rea-sons. As clinical observation hasshown, the biomechanical “dysfunc-tion" of the foot stereotypically caus-es a shortening of the calf muscles.

Given the biomechanical causes ofhallux valgus described above, thetreatment approach of the earlynineties has been adapted to includethe gastrocnemius muscle and (less of-ten) the gastrosoleus muscle in thera-peutic strategies. A follow-up studyconducted as part of a doctoral thesison more than 700 patients with rele-vant foot diseases showed that halluxvalgus coincides with shortened calfmuscles in more than 97% of cases,but that surgical intervention was on-ly necessary in 20%.

With the modern trend toward evi-dence-based medicine straight-jacket-ing the way medical findings are inter-preted, it is likely to be randomizedcontrolled trials conducted elsewherethat will prove whether medical prac-tice based on observation and experi-ence will establish whether medium-term or even long-term benefits forpatients with hallux valgus will evolvein general and specifically by givingconsideration of shortened calf mus-cles. At any rate, podiatrists in the USare increasingly addressing this aspectin their work.

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O R T H O PA E D I C S H O E S I N T E R N AT I O N A L

information about the survey to others."

All stakeholders, especially theusers/potential users or their familymembers/organizations are encour-aged to take part in this survey. Pleasecomplete this survey online or down-load the survey form and send thecompleted survey after selecting the50 most Priority Assistive Products [email protected].

"Should you agree, please fill upyour personal details in order to enable us to keep in touch and informyou about progress related to this endeavour. All survey result will beanalysed anonymously and no person-al identifiers will be linked to the individual responses. All informationwill remain confidential", says ChapalKhasnabis, who is responsible forGATE.

How to get pedorthic products listet in APLTo get products like foot orthoses,footwear for diabetes/neuropathicfoot and orthopaedic shoes or foot -wear in general in WHOs Priority Assistive Products List (APL), it is necessary that many give there votefor those products. For that you justhave to tick the products in the surveywhich you consider important – theones on "Mobility" are listet in thefirst section.

About GATEThe World Health Organization WHOworks on the so-called "GATE"- Program. GATE stands for Global Cooperation on Assistive Technology.Part of this program is the develop-ment and introduction of an index oftypes of aids and appliances, in orderto provide world-wide access to them– thus this program will have a big im-pact on the world-wide treatment with

aids and appliances in the future andthis way also on the work of pedorthic.

In his report on the GATE-Meetingin Cologne in October 2015, Karl-Heinz Schott explained: "FurthermoreWHO and ISPO work on the develop-ment of standards in the area of prosthetics and orthotics. Since theservices of orthopedic shoe technolo-gy also belong to this area, the IVOtries to support the users of aids andappliances within orthopedic shoetechnology in this framework. If youare an ISPO-member yourself, I wouldlike to ask you to contribute at the ISPO that the benefit of pedorthic forpeople will not be overlooked. Weneed pedorthists who are committedto make the topic orthopedic shoetechnology more known and to call attention to the possible benefit oftreatments for people! Internationalcooperation and presence are more important than ever, otherwise thereis the danger that our profession's per-formance for people with foot prob-lems is easily ignored and replaced byless developed and less progressivelow-grade foot treatments."

For further information:

https://extranet.who.int/

dataform/355553/

Kathrin Ernsting is editor for the German

journal “Orthopädieschuhtechnik” and

the English “foot & shoe”.

More than a billion assistive products are needed now – twobillion by 2050. However, today

only one in ten persons in need hasaccess to assistive products (AP). Tochange this scenario, based on thesuccess and learning of Essential Medicines List (EML), WHO is develo-ping a WHO Priority Assistive ProductsList (APL) to assist Member States toplan policies and programmes relatedto the provision of AP. Like the EML,the main goal of this initiative is to improve access to high-quality affordable assistive products.

The World Health Organisation(WHO) is conducting a survey aboutassistive products. The survey is opento all stakeholders and in particular tothose that use assistive products, potential users and their families. It islikewise open to professionals thattreat, supply or fit and manufacturethose assistive products.

Aim of the survey is to establish alist of the 50 top assistive products.Such a list will help WHO membercountries, including your government,in their legislation and health careplanning to make those productsavailable to those that will need it.

To reach many people, the survey isconducted in many languages. "Thesurvey is short and will be closed onthe 3rd of March 2016, so please do itnow", explaines Karl-Heinz Schott whois working on the part of GATE whichrefers to gate, shoes and feet. "I hopethat many will contribute to this factfinding mission. Therefore please passthis information or this email on toyour members and colleagues!".

He emphasizes: "Enable your patients, clients and staff to partici-pate as well and do it yourself. It is ineveryone’s interest, but in particularin the interest of the people who needthe assistive products. Distribute the

The World Health Organisation (WHO) is conducting a survey about assistive products. Aim of the

survey is to establish a list of the 50 top assistive products. To reach many people, the survey is

conducted in many languages. The survey is short and will be closed on the 3rd of March 2016.

Global Survey: WHO Priority Assistive Products List (APL)

@morePlease find online the PDF-File of

the survey for your download.

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M E D I C I N E & T E C H N O L O G Y

In whatever way the analysis of thefeet contact to the ground might beapplied, these questions need to beanswered:1) Which of the above mentioned

parameters should be analysed forthe required task?

2) What is an optimum value for thisparameter?

3) Under which conditions (utilities like shoes, or practice procedures)can the optimum values be rea -lized?All of this can be applied to ortho -

paedics problems, like the load reduc-tion for avoiding pain or even injuries,as well as to sports practice, like theimprovement of movements for get-ting stronger, running faster or jump-ing higher.

With regard to this, it is the aim ofthe present article- to present the main characteristicsof measuring technologies used foranalysing the foot-ground-contact;

- to differentiate the main parametersmeasured by the mentioned techno-logies;

- to discuss the settings of optimal values for the defined parameters,and finally

- to show two examples of typical applications in the fields of ortho -paedics and sports.

Measuring technologyThe history of measuring the inter -action between the human foot andthe ground goes back to the end of thenineteenth century. Marey (1895) de-veloped a pneumatic device for detec-ting the pressure under the forefootduring walking (fig. 1). He placed anair-pocket under each foot which wasconnected to a hand-hold display-unitvia flexible tubes. Thus it was possible

to detect directly the forefoot pressureduring walking. Nowadays, forces aremeasured electronically. That means, aforce-sensitive element is integratedinto an electrical circuit. If a force isacting on the sensor the electronic resistance in the circuit will change.This can be measured by an increase ora decrease of the amperage.

A calibration is necessary to assignthe registered amperage to the actingforce. During the calibration procedureknown forces will act on the sensor byknown weights or by a controllable hy-draulic press, where different steps offorces may be applied. The measuredamperage assigned to the particularforce will be stored in the system, re-sulting in a characteristic curve foreach calibrated sensor. Later, in thereal measurement, these characteristiccurves are used to calculate the cor-rect force value on the base of themeasured amperage.

The calibration procedure is thesame for the measurement of pressureapart from the fact that there is agreater number of sensors disposedover the defined area. Usually, thehigh number of sensors results in a

In many situations in human lifecontact between the human andhis surrounding is realized by the

feet. That is, one foot or both feet have contact to the ground during activities like standing, walking, run-ning or jumping. This may be a directcontact in barefoot situation, or theperson may ware shoes as an interfacebetween the feet and the ground.

However, from a biomechanicalpoint of view this contact may be seenas an interaction of forces. In case ofeasy standing there is, on the onehand, a force acting from the body tothe ground which is caused by the hu-mans body weight. On the other handthere is the ground reaction forcewhich is acting from the ground to thebody. Under static conditions thesetwo forces have equal amount and op-posite direction. Under dynamic situa-tion the ground reaction forces are ingeneral different to the body weightforce. This may range from zero (e.g.in flight phase during running orjumping) up to a multiple of the bodyweight (e.g. during rapid decelerationin landing after jumping).

To analyse the effects of the groundreaction forces on the human bodyforce sensor systems are placed underthe feet. In this way it is the aim toinvestigate whether these forces havepositive or negative influence on theload of the body or on the performanceof the movement, respectively. In ad-dition to the pure force, other bio -mechanical parameters may influencethe effects of the ground contact tothe human body, as follows:- the distribution of the force across agiven area which means pressure;

- the duration of the acting forcewhich means force-time-integral, orcasually called impulse.

The aim of this article is to present the main characteristics of measuring technologies

used for analysing the foot-ground-contact, to differentiate the main parameters

measured by the mentioned technologies, to discuss the settings of optimal values for

the defined parameters, and finally to show two examples of typical applications in the

fields of orthopaedics and sports.

Basics of Foot Pressure Measurements

1 Pneumatic

pressure

measurement

(Marey, 1895).

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difficulties. They developed the so-called multiplex procedure, which isused in every pressure measuring sys-tem until today. The sensors are con-nected in a matrix, in which cables runfrom one sensor to the next in rowsand columns, respectively. The elec-

tronic control system builds up a circuit for each sensor by using theconnection in rows for input and theconnection in columns for output. Inthat way one sensor after the othercan be sampled. This is done on a veryhigh frequency which generally is inthe region of some kHz. Thus, a suffi-cient high sum sampling rate can berealized.

Moreover, there are different typesof sensors on the market. These havedifferent characteristics and thus dif-ferent advantages and disadvantages.Namely, there are strain gauges, capacitive sensors, piezo-resistivesensors and force-resistive sensors.The four listed sensor principles varyin their more or less differences con-cerning accuracy, reliability, tempera-ture dependency, sensor thickness aswell as in their prize.

A user of a measuring systemshould be aware of the possible errorsof the system and know how these errors might be avoided as best as pos-sible. The influence of the tempera-ture, for instance, can be neglected if

2+3 Pressure platform and in-shoe pressure mat (r.).

problem of wiring, since each sensorneeds two cable connections in anelectronic circuit. As pressure plat-forms are provide with more than1 000 sensors, more than 2 000 cableswould be needed. This would result invery high effort and thus in very highcosts.

The idea of Nicol & Henning (1976)was the main step to overcome these

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The force platform

A force platform is able to measure theground reaction forces in three dimen-sions. Usually, it is integrated into thefloor and can be used for all kinds ofmovement, stationary. The biggest ad-vantages of the system are the highamount of accuracy and the possibilityto analyse the forces in horizontal di-rections.

The main disadvantage is the relatively small measuring area in caseof using one unit, especially for fastmovements like running or jumping.Furthermore, a force platform is notcheap, which might be a problem, par-ticularly for using more than one unitto overcome the small area problem.Finally, with a force platform the distribution of force under the footcannot be measured.

The pressure platform

In contrast to the force platform apressure platform (fig. 2) can measurethe force distribution under the foot,but only in vertical direction. Horizon-tal components cannot be detected.Depending on the used sensor type theaccuracy may differ. The problem ofthe stationary use only is the same asmentioned above for the force plate.In contrast to the high sampling rateof a force plate (in general 1 000 Hz)the pressure platform has a muchsmaller measuring frequency which isin the region of 200 Hz. This may be aproblem for high frequency aspects ofmovement like rapid stopping or lan-ding. The spatial sensor resolution onthe plate is however quiet high withapproximately two to four sensors percm². That means, it is highly suitablefor analysing the load on small bony

structures like the meta-tarsal heads.

The in-shoe pressure

mat

Using the two systemsdescribed above, it is notpossible to get informa -tion about the forces orpressure distribution inthe shoe. Therefore, therewill be no evidence aboutthe influence of specialshoes or insoles. To over-come this lack sensormats are placed in theshoe under the foot (fig. 3). For that, mats indifferent sizes as well asspecial shapes like inso-les for stump feet or charcot feet are neces-sary.

In contrast to platemeasurements, one bene-

the measuring conditions are almostconstant at normal room temperature.Exposure to direct sun light in summeror storing the system in unheatedrooms in winter should definitely beavoided. In general, other quality cri-teria like the reliability of the systemis indicated by the manufacturers. Thisaspect is very important if there is aCE-confirmation because the accuracyof any measuring system has to becontrolled in defined time periods in this case. For more detailed infor -mation about the force or pressuremeasuring technologies have a look atthe work of Nigg & Herzog (2007).

Finally, there are different kinds of complete measuring systems. Forthe analysis of the foot ground con -tact three different systems may beused depending on their special application:

4 + 5 Coloured scaled pressure distribution (l.) and force-time- curve in walking.

6 Force-time-curves in six areas of the foot.

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M E D I C I N E & T E C H N O L O G Y

gested partition as he likes. In the ex-ample in fig. 4 six single areas can bedistinguished, namely the heel, themid-foot, the lateral forefoot, the cen-tral forefoot, the medial forefoot andthe toes. For each area the maximumpressure with its exact location and itsvalue is indicated.

In a barefoot measured situationthis display can be used to get infor-mation about the special characteris-tics of the particular foot, for examplelow pressure in the mid-foot region indicates a hollow foot, whereas highpressure indicates a flat foot. The ab-solute pressure peaks show the loca-tion of the foot where problems mayoccur. Thus high pressure values atone of the metatarsal heads (frequent-ly it is number two) may indicate a riskfor pain or even injuries, like microfrac ture of the bone. In conclusion,the efficiency of an individual treat-ment by customized shoe or insolesettings can be controlled by in-shoemeasurements. This task can be real-ized well by comparing the measure-ments be fore and after the treatment.

Force

As described above, force can be measured directly by a force platform.Using a pressure measuring system theforce can be calculated. Pressure p isdefined by force F divided by area A: p = F/A, and therefore force is definedas: F = p*A. Due to the fact that notonly the measured pressure, but alsothe area is known each pressure system releases a force-time-plot. Infig. 5 the force-time-plot from the ground contact of one foot during walking is displayed as an example.

The running time is displayed onthe horizontal axis and the vertical axis shows the acting force. Afterreaching a small peak in the beginningof the curve the force decreases. Thisis called the impact peak and can beexplained as follows: During the firstcontact of the heel to the ground sen-sory elements in different anatomicalstructures (mainly in the skin) recordthe impact. Afterwards, a nerval im-pulse will start to run to the spinalcord via afferent nerves, and fromthere back to the muscles via efferentnerves. This process will take somemsec. resulting in a short delay of thereaction of the muscles for an activecushioning of the impact. The time between heel contact and muscular re-

action is called latency time. In theforce-time-plot it is the time from thestarting point up to the impact peak.Generally, it ranges from 30 to 40msec.

In the following curve progressionthere are two further peaks. The firstone is caused by the passive decelera-tion of the body during landing, thesecond one results from the activeforefoot lift-off. In between the twopeaks there is a more or less load re-duction caused by a knee bending inthe middle stance phase. Usually, thetwo great peaks should be almostequal at a level of approximately 120per cent of the subjects body weight.

If the force curve has an atypicalshape, this may result from a relievingposture caused by pain or a special defective position. Thus a reducedfirst peak may be induced by problemsor pain in the heel region due to a calcaneal spur.

Force-time-integral, impulse

Looking at the pressure only no infor-mation can be retrieved about the duration of the load at a special pointunder the foot. A peak pressure pointmay act both for a short time only orfor a longer time period which hasgreat influence on the risk of develop -ing problems. The force-time-integralis the essential parameter for the ana-lysis of the duration. It will be deter-mined as follows: Firstly, the total force-time-plot is divided into the sixabove explained areas of the foot.Therefore, six single force-time-plotscan be distinguished. In fig. 6 this isdisplayed for left and right foot fornormal walking, whereat there is thesum force-plot (grey) on the top fol -lowed by the single areas from toes (yellow) to heel (pink).

Mathematically, the force-time- integral is defined by the surface areaunder the force-time-curve. Therefore,the integrals are correlated to the sur-faces of the coloured areas in the figure. In the example of fig. 6 thegreatest integral occurs on the rightheel, which can be identified visuallyas well as by reading the value for I = 188,21 Ns.

What does the force-time-integralmean? The best way to answer thisquestion is a physiological approach.Pressure under the foot could be criti-cal, if it is higher than the pressure inthe blood vessels, because the vessels

fit is the high amount of flexibility.The two contact areas, for example thesole of the foot and the foot-bed ofthe shoe or rather the insole, are notflat. Furthermore, it may change dur-ing the ground contact in walking orrunning. Therefore, the flexibility of asensor mat is very important. Unfortu-nately, this demand is in contrast tothe requirement on a high spatial resolution with a great number of sen-sors placed closely together. Generally,the spatial resolution of the in-shoepressure mat is much lower than thatof pressure platforms.

On the other side, the great advan-tage of the in-shoe system is the lowrate of interference by the measuringsystem itself. Almost any situationmay be measured without problemswhich might be crucial for sports applications. The development of theelectronic technologies increased thisadvantage in the past. While data wastransfered via direct cable connectionto the computer 20 years ago, the wayof transferring data has changed frombuffering it on a memory card, to using radio transfer via bluetooth orwlan, thus decreasing the sizes of theelectronic devices to very small boxeswith a weight of less than 100 gram.

Analysis of dataIndependent of the used system – force platform, pressure platform orin-shoe pressure mat – different para-meters may be analysed. On the onehand the pressure cannot be evaluatedby using a force platform, on the otherhand the pressure measuring systemsare not able to determine the horizon-tal components of the forces. Apartfrom that, all other analysis are equaland will be presented commonly.

Pressure

When using a pressure measurementsystem, the first step of analysis is thedisplay of the distribution under thefeet (fig. 4). This is done via a coloured scale for the left and rightfoot. It is universally accepted thatthe scale indicates low pressure bycold colours (grey-blue-green) andhigh pressure by warm colours (yellow-orange-red). Furthermore, amask is laid on top of the foot displayin order to divide the foot in differentsmall areas. This may vary among dif-ferent manufacturers, but neverthe-less, the user may change the sug -

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20 foot & shoe 1/2016

M E D I C I N E & T E C H N O L O G Y

situation by 30 per cent. Publicationsfrom the last years, however, showedthat it is possible to define such absolute values as critical threshold.Already Cavanagh (1991) claimed thatthe absolute value of peak pressure isresponsible for a high risk of ulcera-tion. More recent studies investigatedthe conditions under which relapsedulceration occurs for diabetic patients(Owings et al., 2009; Bus et al.,2013). The observation of a very highnumber of patients yields to quiteconclusive results. They found out thatthere is no relapsed ulceration if peakpressure is less than 20 N/cm². There-fore, the proposal is to take this valueas a general critical threshold for thepeak pressure in the shoe after thetreatment of a diabetic patient.

As mentioned above peak pressureis covering only one but not all as-pects of an appropriate treatment. Thesecond one is the force-time-integralin where the duration of the actingload is considered additionally. Is itpossible to define a critical value forthis parameter as well? To answer thisquestion, the influencing factors ofthe force-time-integral should be con-sidered.

Firstly, the body weight of a personinfluences the force-time-plot in thatway that the curve is higher for aheavy person in comparison to a lightweight one. That means, theforce-time-integral would increase,too. Secondly, the total duration ofthe ground contact influences theforce-time-integral which is affectedby the walking speed. Unfortunately,both factors have negative impact fordiabetic patients, since they are ratherheavy and they are walking ratherslowly. However, this shows that it is

not possible to define an absolutecritical value for the parameter force-time-integral. Nevertheless, the para-meter should always be distributedequally between rear-foot and fore-foot. That means, a measured discrep-ancy should be adjusted by the shoetreatment.

In conclusion, using an in-shoepressure mat for controlling the treat-ment of a diabetic patient orthopaedicshoemakers should pay attention toreduce the maximum pressure under 20N/cm² and to distribute the force-time-integral equal between rearfootand forefoot. The pressure, however, ismainly influenced by the shape andthe material of the insole while theforce-time-integral is mainly influ-enced by the setting of the shoe.Hence, in case of a high impulse valueat the forefoot, a ball roll can be usedto accelerate the final stance phaseduring walking.

Performance diagnostics

in ski jumping

There are various applications of forceor pressure measurements in sports.Many studies dealt with running (Coleet al., 1995; Nigg, 1997; Walther,2005) focusing mainly on the analysisof load. In the field of performancediagnostic and control there are alsoseveral studies present. As examplesthe works of Vetter et al. (2004) inbeach-volleyball and Schnittger et al.(2015) in soccer should be referred. Asan actual example by our researchgroup the measurement of the in-shoepressure in ski jumping will be presen-ted (fig. 7).

One of the most important informa-tion for ski jumping coaches is theforce-time-plot during take-off. In

will be closed and the oxygen supportis broken. This may result in a tissuedieback. This however, is much morecritical, if the vessel is closed for alonger period of time. A short stop ofblood flow caused by a single pressurepeak is less critical. Since the durationof the acting load is part of the force-time-integral, this is a salient para -meter.

ApplicationsTreatment of the diabetic foot

One of the most common applicationsfor pressure measurement systems inorthopaedics is the treatment of thediabetic foot. In case of neuropathydisease the patient is not able to re -gister pressure under his feet. Conse-quently, there is no defence mecha-nism to avoid permanent load at asingle location.

During walking or even runningthere would be a high rate of repeatedimpacts so that blood flow may be in-fluenced and the oxygen supply maynot be guaranteed. Therefore, the riskfor getting ulcers is very high for diabetic patients. To avoid this, ortho -paedic shoemakers have to realize appropriate treatment by customizedshoes and/or insoles. The in-shoepressure mat system is the instrumentused to control the treatment in orderto reduce the risk of ulceration.

From the biomechanical point ofview, it would be desirable to definecritical values for the peak pressureand for the force-time-integral. Inother words: Are there absolute valuesfor both parameters which should notbe exceeded after the treatment?

In the past, health insurances inGermany demanded a reduction of thepeak pressure measured in barefoot

7+8 Measurement of pressure and force-time-curves in ski jumping.

Page 21: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

fig. 8 the complete force-time-plot from inrun, take-off, flightand landing is displayed. Thereby, the red curve represents theright foot, the green one shows the left foot and the sum of both is displayed in blue. At the moment of the take-off(approx. from 6 to 7 sec. after the start) it is important to lookexactly at the time of peak force. It should neither be to earlynor to late, otherwise an optimal take-off is not possible.

Furthermore, the relation between left and right foot aswell as between rearfoot and forefoot are investigated as thishas a direct impact on the body position in the early flightphase. One possible problem for athletes may be a strongpush-off over the forefoot with less contact on the heel. Con-sequently, it is more difficult to reach quickly the lent forwardV-position in early flight. Natrup (2015) investigated the ef-fects of insoles with lateral forefoot and heel increase on thepressure distribution and the force during take-off. As a result,the insoles constructed in that way have a positive effect onthe power of the take-off. Finally, this results in longer jumpdistances.

In conclusion, the described application in ski jumping isonly one example, but it shows very impressive, how the pres-sure measuring system can be used to analyse sports perfor-mances. In that way, it may be very helpful for coaches andtheir high- level athletes to become more successful.

References

– Bus, S.A. et al.: Effect of custom-made footware on foot ulcer recur -rence in diabetes, Diabetes Care, 36, 12, 4109-4116, 2013

– Cavanagh, P.R.: Footwear and ulcer healing, Diabetic Medicine, V.8, I. 3, p. 289, 1991

– Cole, G.K. et al.: Internal loading of the foot and ankle during impactin running, J. Appl. Biom. 11, 25-46, 1995

– Marey, J.E.: De la locomotion terestre chez les bipedes et les quadru-pedes, Journal de l�anatomie et de la physiologie, 9, 42, 1895

– Natrup, J.: The effect of in-shoe lateral forefoot and heel increase onthe take-off phase in ski jumping, Bachelor Thesis, Muenster, 2015

– Nicol, K., Hennig, E.M.: Time dependend method for measuring forcedistribution using a flexible mat as capacitor, Komi, P.V.: BiomechanicsV-B, Baltimore, 433-440, 1976

– Nigg, B.M.: Impact forces in running, Curr. Opin. Orthop. 8, 43-47,1997

– Nigg, B.M., Herzog, W.: Biomechanics of the musculo-skeletal system,3rd Edition, Wiley, 2007

– Owings, T.M. et al.: Plantar pressures in diabetic patients with foot ul-cers which have remained healed, in, Diabetic Medicine, V.26, I. 11,1141, 2009

– Schnittger, H, Natrup, J.: Sprungkraftdiagnostik und Trainingssteue-rung im Fußball, Hightec in Training, Wettkampf und Ausbildung, dvsFußball, Erlangen, 2015, (in press)

– Vetter, K., Voigt, H.F., Natrup, J., Nicol, K.: Ein innovatives Verfahrenzur Bestimmung von Bodenreaktionskräften im Beach-Volleyball, Leistungssport, 5, 39-43, 2004

– Walther, M., Reuter, I., Leonhard, T., Engelhardt, M.: Injuries and response to overload stress in running as a sport, in: Orthopaede, 34,399-404, 2005

Dr. Jörg Natrup has a PhD in sports science and was an assi-stant professor at the „Institut für Bewegungswissenschaften“(Institute for Motion Science) in Münster, Germany. Today heworks as a scientist for GeBioM in Münster, Germany. His key ac-tivities are biomechanics, load analysis of the locomotor systemwhen walking, running, sitting and lying down as well as the el-ectronic measuring technology.

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Page 22: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

sed custom-made therapeutic devices,Jaron's family simply cannot afford thenecessary treatment. Following manyconversations and in-depth correspon-dence between Micha Oelsner Hartmut Seidich, Mr Seidich agreed to take onJaron's treatment free of charge. Bothparties involved firmly believe an am-putation of the entire lower leg shouldreally be the very last resort.

Obviously, with the patient livingthousands of kilometers away, with noopportunity for team Seidich to perso-nally examine the little patient, the

The treatment up to nowGerman trained pedorthist, Micha Oelsner, (see "Talking with..." edition2/2011, page 30), who has her works-hop in Durban, KZN, South Africa, hasbeen in cooperation with Upper Manu-facturers Seidich in Germany for quitesome time. She supplies and takes ca-re of Jaron. Unfortunately, in SouthAfrica, most of the materials and machines needed for adequate andcomprehensive pedorthic treatmentare not available locally. Also, consi-dering the very high cost for speciali-

22 foot & shoe 1/2016

W O R K S H O P

Jaron's mother was nine weekspregnant, when she found outthat she was expecting a child. At

that time she was taking several drugs,amongst them also antibiotics, totreat an illness. When the antibioticsdid not help to treat her influenza, thedoctors examined her blood and onlythen discovered her unplanned preg-nancy. Because of her exposure to somany drugs, the mother had herdoubts about carrying out the child –but the test results showed "Downsyndrome negative".

However, a routine anomaly ultra-sound scan at 21 weeks revealed anunderdevelopment of the left foot ofthe fetus.

Situation so farJaron is completely healthy, except forhis left foot. According to the treatingdoctors only his heel and ankle are os-seously developed. At this stage, ho-wever, his mid-foot and fore-foot havenot been osseously developed. Despitehis limitations, Jaron is able to standon his toes with both feet.

In South Africa adequate pedorthictreatment is generally not available.Without the required treatment, theprogressive uneven growth of both hisfeet are expected to impair his gait. Inthe medium to long term chronic pro-blems of his knees and hip joints willbe inevitable.

The treating doctors in South Africahave only recommended amputation ofthe entire left lower leg – a huge shockfor the mom! Having to raise her twosons as a single mother, Jaron's momcannot afford a trip to Europe to haveJaron treated there. Jaron's familydoes not have any health insurance, acommon situation for the majority ofSouth Africans.

Jaron lives in South Africa and is now three years old. His left foot is not fully developed and his

mother cannot afford the necessary orthopaedic shoe technological treatment. Help has come

from an international cooperation of health professionals that made the first treatment possible.

The long term vision is to continue treating Jaron by getting even more supporters involved.

Treatment Possible Through International Cooperation

Name: Jaron Du Preez

Date of birth: 25 January 2013

Diagnosis: Unconfirmed – doctors

suspect either ABS or

chromosome 7

Treatment: Internal shoe upper with

forefoot replacement

and exchangeable carb-

on sole

Participating companies:

Seidich Schäfte (Germany),

Orthopaedic Foot/Shoe Specialist

(South Africa),

Superfit (Switzerland)

Donations

To ensure future supply, Jaron's mother relies on dona-tions. For this purpose, a trustaccount was established:MM Du PreezFirst National BankFNB SWIFT code: FIRNZAJJA/C # 62154121744Branch # 250142

Page 23: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

The doctors have not found out yet what exactly prevents Jaron's

left leg from growing.

Micha Oelsner took the necessary

measurements in Durban, South

Africa and made a plaster cast and

a foam imprint and sent it to Sei-

dich in Germany.

conditions for optimal treatment arefar from ideal. In this case, however,the experienced pedorthist, based nowin Durban, 600 kilometres away fromJaron's home, is there to help.

The team began its search for anoptimal solution 10 000 kilometersaway from Jaron's home in the Germanarea "Ruhrgebiet", after having recei-ved a detailed medical report, blueprints, foam impressions, measure-ments, images, several videos showingJaron's gait, and an exact plaster moldof the left foot. In order for team Sei-dich to manufacture the last, (an exactreplica of Jaron's left foot), the accu-rate and perfect preparatory work sup-plied by Micha Oelsner, was absolutely

According to the

specifications of

Micha Oelsner the

last, an exact replica

of Jaron's left foot,

was manufactured

there. This worked

out that well only be-

cause of Micha Oels-

ners excellent prepa-

ratory work.

More information:Leipziger Messe GmbH, Project Team OTWorld Tel: +49 341 678-8260 · E-mail: [email protected]

Be sure not to miss

the 2016 industry event

of the year!

The OTWorld is the foremost

global event of the orthopaedics

industry. This year in Leipzig you

can look forward to gaining unique

insights into current industry

developments. From orthopaedic

shoe technology to podology,

from prosthetics and orthotics to

compression therapy, this is the

ideal place to be for a professional

exchange of ideas with doctors,

technicians, therapists and

podiatrists.

THE NEXT

STEP IN FOOT

HEALTH

Page 24: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

24 foot & shoe 1/2016

W O R K S H O P

dich has been hand-crafting orthopa-edic uppers and high-quality custom-made shoes for three generations. Formany years the company has passiona-tely been supporting humanitarianprojects for children – mainly in warzones and areas of conflict.

Comparable to a forefoot amputationChoosing a holistic approach by con-sulting several medical-professionalexperts, the decision was made totreat the under-developed left foot li-ke a forefoot amputation. For that rea-son, instead of manufacturing ortho-paedic custom-made boots, an inter-nal shoe (inner shoe) with a forefootreplacement device (Inlay), was thechoice of treatment. Such a device willallow Jaron to wear regular shoes, pos-sibly also sandals in the summer,which is a huge advantage in a hot cli-mate like South Africa.

Considering further growthThe uneven growth of both feet pre-sent another problem. Whereas theright foot is growing age-appropriate-ly (at this age that means fast), theleft foot is developing very slowly. Un-even growth aside, Jaron still has towear the same size shoes on both si-des. Most off-the-shelf shoes differnot only in length, but also in solethickness and heel height, accordingto different styles and size categories.Jaron's shoes will always have to beone hundred per cent identical, to en-sure the child's pelvis is even. A falseleg-length-discrepancy can result inpelvic obliquity and cause damage tothe hip. In this case, the total thick -

In order to consider the growth of both feet,

the internal shoe has been constructed in a

way that the exchangeable carbon sole and

the lacing make the adjustment of the

shoes possible.

The leather cap worked in for the stiffening is made of cavern-tanned calf leather. This cap has been

worked in the upper with an interior glue based on potato starch that is breathable once dry.

Here it has been decided to treat Jaron's foot like a forefoot amputation. An internal shoe made of pol-

lutant-free lining leather (interior lining of the shaft and interior covering of the forefoot replacement)

was made. The Valonea-calf leather has been tanned purely herbally and is especially skinfriendly and

very sweat-absorbing.

@morePlease find online the videos anda photo gallery of Jaron, histreatement and the production ofthe shoe that grows with him.

crucial for achieving a very good result.

Treatment was implemented by apprentices Jan Droste and Dustin Seidich, under the supervision of anpedorthist (German "Orthopädieschuh-macher-Meister") and a Master ShoeMaker. Shoe & Upper Manufacturer Sei-

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25foot & shoe 1/2016

W O R K S H O P

is expected to last for about two years.If future growth of the left foot

does not accommodate further use ofthis internal shoe, a new one has to bemade according to the new measure-ments. In order to monitor the growthand development of Jaron's feet andthe correct fit of the internal shoe, Ja-ron will have to see Micha Oelsner fora follow-up consultation every sixmonths.

MaterialSpecial care was taken while choosingthe material, to assure that every ma-terial in contact with the skin is pol-lutant-free. As leather-lining (lining ofupper and forefoot replacement),high-quality, purely herbally tannedValonea-calf leather from Ecopell (Ger-many), a producer from the German re-gion "Allgäu", was used. This leatheris particularly skin-friendly and verysweat absorbant.

The enforced leather heel/ankle capis made of cavern-tanned calf leatherfrom the traditional tannery Rudolphin Thüringen (Germany). This cap has

been attached to the upper with pota-to-starch-based glue that remainsbreathable once dry.

The leather used for the upper ismade from the finest Nappa leatherfrom an Italian tannery and complieswith the regulations of the GermanMedicinal Devices Act.

It was a joy to correlate with ano-ther supporter of Jarion's treatment,Superfit, the Swiss producer of child-ren's shoes. They were extremely hel-pful and very pleasant to work with.The idea was to supply shoes from theSuperfit range that are as durable andhigh-quality as possible. In a non-bu-reaucratic way Superfit provided sever-al pairs of shoes in different sizes fromthe same range.

The forefoot replacement was fittedinto the smallest size shoe that cur-rently fits the right foot. The larger si-ze shoes will in future accommodatethe growth of Jaron's feet.

Hartmut Seidich, owner of the com-pany Seidich Schäfte in Herne, Ger-many, specializes in severe orthopaediccases and in exceptional uppers for cu-stom-made footwear. He is a lecturerfor production of shoe uppers at theAcademy of Craft in Dusseldorf. His new and detailed textbook of "Manufacturing Uppers" will be publi -shed by C. Maurer Fachmedien, Geislin-gen, Germany, soon. Hand-made shoeswith Seidich’s uppers are both worn byvictims of land mines or congenital deformities and by princes or Hollywoodstars. (www.seidich.com).

ness of 12 milimeters, that makes upthe internal shoe device's sole, inser-ted in the left shoe, has to be conside-red. To achieve an even gait, the off-the-shelf insert of the left shoe needsto be removed, consequently reducingthe heel-difference slightly. On the op-posite (right) side, a cork wedge withthe correct thickness (about eightmilimeters) is then glued underneaththe off-the-shelf insert to compensatefor the heel-difference.

If however, Jaron is to wear the sa-me shoe size on both – differently si-zed – feet, the internal shoe has to beadjustable and adaptable to futureshoe sizes, as Jaron grows older. Asthe healthy right foot grows in length,the left foot also needs "to grow" at acertain stage. Usually in a case likethis, it is common practice to manu-facture a completely new device. InJaron's case, this is not an option dueto logistical and financial constraints.The crucial technical solution to thischallenge is a carbon spring, imple-mented into the internal shoe. By ins-erting the carbon spring inside a solidpouch (glued and stitched) at the bot-tom of the internal shoe, firm positio-ning is achieved, eliminating any side-movement. The carbon spring can ea-sily be removed and exchanged for alonger carbon sole by simply removingtwo rivets. The carbon spring has beenmolded in a specific way, allowing fornatural toe off of the underdevelopedfoot.

The entire foot is firmly held in place by a specially designed internalshoe upper, equipped with a high andslightly enforced heel/ankle cap, inorder to support the foot all aroundand to prevent overloading of the ten-dons. Jaron's tendons might not befully developed and need extra sup-port. The total weight of the forefootdevice and the internal shoe is only165 grams.

An eight milimeter latex cushionhas been placed in the toe area of theforefoot device. In case of a growthspurt it can easily be removed. Any po-tential increase in leg circumferencecan be acommodated with the adju-stable lacing. In addition, a flexibleelastic band has been attached to therear closure of the internal shoe upper,allowing for further expansion. Conse-quently, depending on the growth ofthe left foot, this internal shoe device

Jaron plays and runs excitedly in his new shoes, in the

left one with the green laces the adjustable internal

shoe was placed.

Page 26: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

The new Flexam can do every-

thing the "classic" can. But

the touchscreen offers more:

With the new dust-free touch-

screen control panel, you now

have the instruction manual

to hand whenever you need

it. Another new feature is the

handy energy-saving standby

mode. The new Flexam can

now be operated in your de-

sired language. Cleaning

times can also be saved as re-

quired. Parameters such as

different working levels can

be set simply by touch. The

26 foot & shoe 1/2016

A N N O U N C E M E N T S O F T H E I N D U S T R Y

Due to translation errors of

the editorial staff the article

The material "Astro form" is

made of light cellular rubber

with a unique composition of

properties. It is very soft and

resilient, yet still keeps its

shape! With "Astro form 8"

and "Astro form 15", this ma-

terial is now available in two

types. Both are made in Ger-

many (Nora systems GmbH),

have a closed cell structure,

are hygienically washable and

optimally thermoformable,

and also exhibit particular

softness and high permanent

resilience and recovery capa-

bility after processing.

Whereas "Astro form 8" is

so soft that the Shore A hard-

ness is scarcely measurable,

"Astro form 15" is firmer and

tighter with a Shore A hard-

ness of about 15 and a densi-

ty of 0.32 g/cm³, and ex-

hibits even greater recovery

capability. The practitioner

can choose between these

two types depending on the

load conditions, use, and

area. "Astro form 15" is above

all suitable for areas subject-

ed to greater loading like in-

dividual toe elements, heel or

forefoot cushioning, insole

pads, and others.

The material is interesting

above all for orthopaedic ap-

plications that require com-

bined bedding and cushion-

ing properties in the struc-

ture. When heated, "Astro

Nora systems GmbH

form 15" can be very easily

drawn, placed over the work-

piece, and subsequently heat

molded.

The benefits of "Nora As-

tro form 15" are self-evident:

particular softness, excellent

recovery capability after com-

pression, low compression,

outstanding cushioning prop-

erties, thermoformable at ap-

proximately 110 to 130 centi-

grade respectively 230 to 266

degrees Fahrenheit, hygienic

and disinfectable due to the

closed cellular surface, easy

to die-cut and finally excel-

lent bonding properties.

Ideal areas of application

for "Astro form 15" are cush-

ioning in orthotics and pros-

thetics for example in fore-

foot replacement, heel and

forefoot cushioning, Haglund

heel cushioning, cushioning

layer for diabetes-adapted

footbed, heel spur cavities for

heel spur inserts and upper

cushioning like for peroneal

or ankle caps.

Further information

www.nora-shoe.com

Thanks to its thermoplastic properties, "Astro form 15" optimally

moulds itself to the second ply during deep drawing without having

to be heated separately. The permanently resilient properties of this

material are retained to the maximum extent.

THE INTERNATIONAL JOURNAL

FOR FOOT ORTHOTICS

www.foot-and-shoe.com/newsletter

perfect workplace for each

employe can be created by

generating multiple user pro-

files.

The service department

monitors various key parts of

the machine online and noti-

fies you as soon as a mainte-

nance check is required or a

part needs to be replaced. All

information on features can

be found online.

Further Information

www.Ottobock-josamerica.com

Ottobock | Jos America

The new "Flexam" with touchscreen control.

Effect of proprioceptive in-

soles on patients with cervi-

cal spine syndrome

Original Research Report

by Simone Werner et al

foot&shoe 2/2015, page 38

ff.

has been completely revised

and is now available on-line

in the updated version.

Please excuse our problems!

On our own behalf

Page 27: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

27foot & shoe 1/2016

A N N O U N C E M E N T S O F T H E I N D U S T R Y

Think Schuhwerk GmbHC. Maurer Fachmedien

From May 3 to 6, 2016 the

global O&P sector meets up at

OTWorld, International Trade

Show and World Congress in

Leipzig, Germany. The trade

show and the congress will

also have a section for ped -

orthics.

"foot&shoe" will also be at

the trade show. If you come

to Leipzig, you will find us at

the booth of C. Maurer

Fachmedien (1-H17). We will

present the latest issues of

foot&shoe as well as the new

textbook "Pedorthics". We are

looking forward to meet you

to discuss and share ideas for

the further development of

our journal.

The area of OTWorld that

focuses on the wholesale and

retail trades offers visitors an

opportunity to look beyond

the confines of their own

horizons. Major suppliers will

be represented at the trade

fair. The forum on future con-

cerns will include lectures on

sales and marketing, as well

as on staffing and finances,

and a special show devoted to

tips and tricks relating to

shop fitting and product dis-

play.

Pedorthists will get an

overview of the market at

OTWorld. In both trade fair

and congress a comprehen-

sive insight into the neigh-

bouring fields of expertise

that impact on orthopaedic

footwear technology will be

offered.

Premiere in the shoe industry.

Think! is the first shoe pro-

ducer that has been awarded

the "Austrian ecolabel" in Oc-

tober. The model "Chilli" has

been certified, a black lace-

up from the ladies' shoes col-

lection.

The "Austrian ecolabel" is

considered as one of the

strictest sustainability cer-

tificates in Europe. In order

to meet all of the criteria, the

product is not only checked

during the final production.

Also the production of the

used materials has to be car-

ried out in a verifiably eco-

friendly way. Additionally the

distinguished products have

to meet ambitious social cri-

teria.

The certification of the

lace-up "Chilli" is another

step for Think! towards a pro-

duction chain that is tradi-

tionally sustainable and eco-

friendly.

"We have gained valuable

insight through the very de-

manding and time-consuming

certification, that we will use

for the development of our

new collections", Walter

Breuer, the managing director

of Think! promises.

Register

now -

its free!In our new free

quarterly newsletter

we inform you about

recent developments

in the industry and new

scientific findings and

we provide practical

tips for the trade.

We also let you know

about interesting offers

of further education

and events on a global

scale.

THE INTERNATIONAL JOURNAL

FOR FOOT ORTHOTICS

Register

now -

its free!

www.foot-and-shoe.com/newsletter

Page 28: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

R&OC 2016, the 6th edition of

the annual event is the only

one platform showcasing the

rehabilitation equipments,

assistive technology and

prosthetics & orthotics prod-

ucts in China, serves to fea-

ture the latest state of devel-

opment of the Chinese indus-

try and introduces the worlds

latest technologies to the

Chinese market. The combina-

tion of International Reha -

bilitation Canton Forum

(IRCF) makes the R&OC an

optimal trading and dialogue

platform for professionals,

market leaders, suppliers,

dealers and innovative new-

comers from China and across

the world.

The last fair attracted the

presence of 186 well-known

companies from 21 countries

and regions that covers 481

booths, gathering about

13 393 industry professional

visitors from 59 countries and

regions. It is expected to

have about 600 booths con-

sisting of 250 exhibitors in

R&OC 2016. The concurrent

event International Rehabili-

tation Canton Forum (IRCF)

was held by International

Society of Physical and Reha-

bilitation Medicine (ISPRM).

IRCF 2015 forum triumphant-

ly invited 127 renowned do-

mestic and overseas experts

to make academic speeches

and share their latest re-

searches to 1 362 professional

audience, while an expecta-

tion of 300 illustrious experts

Upcomming events

C O N F E R E N C E S & C O N G R E S S E S

foot & shoe 1/201628

Kathrin Ernsting is editor for

the German journal “Orthopä-

dieschuhtechnik” and the

English “foot & shoe”.

Every two years, the global

O&P sector meets up at

OTWorld, International Trade

Show and World Congress.

More than 20 000 visitors

come to discuss the latest re-

search and development work

and practical experiences

with speakers and exhibitors

from all over the world. Inter-

disciplinarity is focussed at

OTWorld: all disciplines

involved in the use of artifi-

cial aids in the treatment of

patients meet here. These in-

clude, for example, ortho -

paedic technicians, ortho -

paedic shoemakers, engi-

neers, doctors, physiothera-

pists and occupational thera-

pists. The Congress involves

many distinguished delegates

and its attendance list reads

like a Who's Who of the

sector. International profes-

sional associations in the

sector meet up in the Global

Networking Area, a platform

for information and commu-

nication, to discuss current

issues in the sector at an in-

ternational level and to share

their work and activities.

“We are delighted that we

are again able to host the

worlds largest gathering of

professional associations in

our sector. The Global Net-

working Area offers an ideal

platform for making many

new personal contacts and

establishing new networks,

which can and will impact

positively on our shared

future long-term,” insists

Klaus-Jürgen Lotz, President

of the German Association of

Orthopaedic Technology.

“I am, moreover, very

pleased that we shall be

seeing greater international

participation among what is

also the biggest gathering

of young orthotics and pros-

May 8 – 10, 2016: OTWorld, Leipzig

and 3 000 attendances in

2016.

A great success for all

parties concerned, featuring

250 exhibitors of 600 stands,

20 000 square meters includ-

ing exhibition area and the

forum. Besides, there are

more than 25 000 domestic

and overseas visitors expect-

ed in R&OC 2016.

Further information

http://en.cantonrehacare.com

thetics. Alongside German

students and trainees in tech-

nical orthopaedics and medi -

cal students, young members

of the sector from France and

the Netherlands are now

also invited to the Youth

Academy,” explains Professor

Frank Braatz of the Private

University of Göttingen / Uni-

versity Medical Center Göttin-

gen (UMG) and Congress Pres-

ident at OTWorld 2016.

Further information

http://ot-world.com/

The FIP/IFP is an internation-

al not-for-profit association

focused on global leadership

and the development of podi-

atric medicine around the

world. Working together col-

laboratively with leaders of

the podiatry profession, the

Federation enhances the po-

diatric profession through the

sharing of knowledge, prac-

tice and research among

member countries. The FIP

World Congress of Podiatry is

held every three years and

attracts participants from

around the world, including

podiatrists in private prac-

tice, the public sector, the

educational stream and stu-

dents. As well, you can expect

to meet vascular surgeons,

nurses, diabetologists and

other members of the medical

team. The exhibit hall is an

integral part of the World

Congress that enables dele-

gates to see a wide array of

foot related products and ser-

vices from around the world.

With an expected 1200 active

participants, this will be the

largest gathering of inter -

national foot and ankle

practioners/specialists. This

meeting is the forum for pro-

May 26 – 28, 2016: FIP-IFP Congress, Montreal

fessionals, industry and aca -

demia practicing in this field

to interact.

Further information

http://registration.

cgi-pco.com/WCP2016

March 25 – 27, 2016: Rehacare & Orthopedic China, Guangzhou

Page 29: THE INTERNATIONAL JOURNAL FOR FOOT ORTHOTICS · the function of the foot, sometimes re-ferred to as orthotic insoles, inlays, in-soles, custom-made insoles, orthotics or orthoses

Iris Burtscheidt and some examples of her work.

Talking with...

Name: Iris Burtscheidt

Marital status: married

Date of birth: 05/04/1976

Profession: Orthopaedic Shoe Technician / Pedorthist

Place of residence: Eupen, Belgium

Company and position: Managing DirectorBurtscheidt-Orthopädie PGmbH

Place of work: Eupen, Belgium

this is not understood anymore in ourindustry.

My next aim is...to deal with modern media like Face-book, Twitter, etc.

Shoes are for me...passion! A high-quality and beautiful shoe canthrill me. Unfortunately the quality ofready-made shoes is getting worse,since the end consumer wants to havemany and low-priced shoes.

I would like that the shoe industry...pays more attention to quality. Manyfoot problems are caused by low-quali-ty shoes, for example the lack of steeljoints, bad stiffeners...

Interview by Kathrin Ernsting

I came to the shoe trade...through my parents. My grandpa opened the company in 1945, my father took it over in 1980. I used tobe a lot in the workshop when I was little, sometimes I helped. In 1994 Ibegan my education in my parents'company. Since 1995 my husband hasalso worked here.

What I like about my job...is the diversity. We work with patientsin order get the best-possible solutionfor their foot problems. Also manualskills and creativity are needed, sothat the limitation is not "visible".And I also enjoy the office work.

It is very important for me...that the patient is satisfied with ourwork and that he can walk better. I also pay a lot of attention to custom-made work, since every patient shouldbe treated individually. Unfortunately

Job history:1994 A-levels1995 – 1998 Koning Willem College I,'s Hertogenbosch (NL)1999 – 2000 NOV Utrecht (NL)Practical education in company of parentsIn October 2000 successful exam of orthopaedics in Bruxelles (B)2015 Taking over of family business

A typical day in my professional life:I begin my day at 6 o'clock, check mymails and do the book-keeping. In themornings I usually work in the work -shop, since I am responsible for theproduction of insoles together with myfather. Most of the afternoon I work inthe practice and do office work.

Q U E S T I O N A I R

foot & shoe 1/2016 29

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30 foot & shoe 1/2016

Specialized orthopedic devices forstabilizing and offloading thefoot are often used to support the

rehabilitation process after foot sur-gery [2]. There are different types ofshoes prescribed after surgery, such asthose specialized for wound manage-ment or with offloading functions. InGermany, these therapeutic shoesmust meet essential requirements toreceive an official number in the German register of medical technicalaids and it is therefore necessary totest their quality and functions. Wound management requires antibac-terial material and postoperativeshoes have to be firmly affixed to thefoot to reduce loading in the forefootarea. Postoperative shoes must also becomfortable, even if the foot is banda-ged. Forefoot offloading shoes areused when load has to be taken off theinjured area but the patient needs tostay mobile, for example, after halluxvalgus surgery.

How much the injured area is off -loaded can generally be justified bymeasuring plantar pressure. In additi-on to plantar pressure, however, mult-idimensional stresses like bending andtorsional moments also act on thefoot.

After aggregating their calibrationresults, they concluded that the insolemeasuring system is able to easily andreliably measure bending and torsionalmoments at the forefoot [5].

This study analysed the effects oftwo different offloading shoes on ben-ding and torsional moments at the fo-refoot: the Relief Dual offloading shoe(Darco Europe GmbH, Raisting, Ger-many) and a competitor post-op shoe.Both are postoperative offloadingshoes, but their designs are very diffe-rent. The competitor shoe is indexedin the German register of medicaltechnical aids, which is a preconditionfor the reimbursement through thehealth insurance. The aim of the studywas to investigate whether the mecha-nical conditions present in the twoshoes have comparable or significantlydifferent influences on stress at theforefoot.

The insole measuring system vebi-toSCIENCE (vebitosolution GmbH,Steinfurt, Germany) was used to moni-tor bending and torsional stress. Thissystem uses 5 parameters to measure ashoe’s functional limitation and fore-foot offloading effect.

22 healthy subjects (mean age: 35years; 9 female, 13 male) participatedin the present study. Loading curvesfor 30 consecutive gait cycles were ac-quired from each test person, afterwhich the mean values were calcula-ted. The curve of bending and torsio-nal moments were measured at fivedifferent sensor positions and parame-ters like maxima, range and alterna-

Analysis of Bending and Torsional Stresson the Foot in Different Offloading Shoes

Original Research Report

Nora Dawin, M.Sc.1,2; Nicole Dirksen, M.Sc.2; Philipp Buss, M.Sc.2; Klaus Peikenkamp, Prof. Dr. habil.2

Abstract

This study compares the bending and torsional stress acting on the foot in the Darco Relief Dual offloading shoe to that of an al-

ready licensed competitor. Levels of functional limitation and forefoot offloading were analysed in 22 healthy subjects

(9f, 13m; 35 ± 8y) using the vebitoSCIENCE measuring system. 30 gait cycles were monitored and the mean values calculated for

selected parameters. The Darco Relief Dual significantly reduced (p<0.05) maximum dorsal extension moments at MTP I and V. The-

re was also a significant reduction in the range of motion at MTP V and a significant decrease in the total load on MTP I and V over

the entire gait cycle. In the competitor shoe, a significantly reduced maximum plantar flexion moment and alternating load were

measured at MTP I and DIP I.

Keywords: Bending moment, torsional moment, stress, offloading shoes

Bending moments, which are calcu-lated by multiplying the acting forceby the respective lever arm, causebending deformations in the shoe; orrather, on the foot in the shoe. If, forinstance, the forefoot is extended dor-sally with respect to the hindfoot, the-re is an acting dorsal extension mo-ment. In the case of a cyclical move-ment like walking, alternating loadingoccurs in the form of both dorsal extension and plantar flexion moment.Alter nating load cannot be detectedby conventional pressure measurementsystems [5].

The first findings on bending loadsacting on the foot were published byArndt et al. (2002) [1]. The authorsconducted an in-vivo study in whichstrain gauges were surgically implan-ted into the second dorsal metatarsalbone. These measured strain on the2nd metatarsal head during walkingand were capable of detecting bothtensional stress and compressionstress. In the past, invasive procedu-res such as this were the only way tomeasure bending and torsional stres-ses acting on the foot in shoes. Howe-ver, a new, non-invasive insole measu-rement system, developed at the Bio-mechanics Research Laboratory atMünster University of Applied Sciences(Germany), is now available.

Stief and Peikenkamp presented thefirst results obtained with the new in-sole measuring system in 2015, de-monstrating that it could detect plan-tarflexion stress followed by dorsiflexi-on stress during each gait cycle [4, 5].

S C I E N C E

1 vebitosolution GmbH

Am Campus 2

48565 Steinfurt, Germany2 Fachhochschule Münster

Labor für Biomechanik

Am Bürgerkamp 3

48565 Steinfurt, Germany

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31foot & shoe 1/2016

The measuring insoles were placedin the shoes and cables were affixed tothe participants’ legs with flexibleVelcro® straps. To avoid distorted re-sults due to fatigue or testing order,the order of shoe conditions testedwas randomized. Subjects wore thedifferent test shoes on their right foot.On their left foot, they wore an AdidasSamba with additional height compen-sation matching that of the offloadingshoe being tested. The measuring in-soles were worn on both feet. The sy-stem requires an initially unloadedstate, which was measured with sub-jects sitting on a raised chair with legsand feet hanging and immobile. Themeasurements were taken on a Sprin-tex slat belt treadmill (SPRINTEX Trai-ningsgeräte GmbH, Kleines Wiesental,Germany).

Before data acquisition, partici-pants were given five minutes of fami-liarization per shoe condition, duringwhich they walked on the treadmill ata self-selected speed (minimum of 2.5km/h). The velocity chosen by thesubject during this period of fami-liarization was maintained for the fol-lowing trials. Measurement of bending

aids, which is a precondition forthe reimbursement through thehealth insurance (medical tech -nical aids classification numbergroup: 31.03.03.). The Darco Re-lief Dual did not have an medicaltechnical aids classification num-ber at the beginning of this stu-dy. The offloading shoes are verydifferent in design. The competitoris a closed model with cushioned in-terior, featuring a rigid, full outsolewith a double-rocker. The Relief Dual isan open shoe, which protects the toes,with an extended outsole. The outsoleis made of two different materials witha continuous, rigid stiffening sole.Both shoes are fastened to the footwith Velcro.

In total, seven shoe sizes of the Re-lief Dual (34 female – 48 male) and fi-ve sizes of the competitor (37 – 46)were compared. Heel heights of thecompetitor shoes ranged from 30 – 32mm and the Relief Dual from 31 – 39mm.

Bending and torsional

insole measurements

The vebitoSCIENCE insole measure-ment system described above was usedto measure bending and torsionalstress (5 sensor positions, 125 Hz, 16 bit).

The vebitoSCIENCE measurementsystem was developed by the Bio -mechanics Research Laboratory, Mün-ster University of Applied Sciences, Germany. Strain gauges are fixed to a specially shaped flexible layer in theinsoles. The purpose of the specialshaping is to detect bending and tor-sional loads independent of the medi-al and lateral forefoot. Mirror-invertedand interconnected strain gauges canbe found on both the upper and bot-tom surface. The interconnection ofthe strain gauges into half bridge cir-cuits for bending and full bridge cir-cuits for torsion allows both loads tobe measured at the same time. Themeasuring frequency is 125 Hz. Sen-sors are placed proximal to metatarso-phalangeal joints I and V (MTP I andV), proximal to the distal interphalan-geal joints I and V (DIP I and DIP V)and distal to the processus calca -neus(see Figure 2). Data are trans -ferred wirelessly to a notebook viaBluetooth. The calibration results pre-sented a coefficient of determinationof R² > 0.999 and a linearity factor ofalmost 1.0 [5].

S C I E N C E

ting stress were analysed statistically.

MethodsParticipants

The loads occurring under the diffe-rent shoe conditions were recorded intrials with 22 test persons (mean age:35 ± 8 years, between 25 and 52). Ni-ne of the 22 subjects were female. Ageand normal, physiological gait patternwere the selection factors for choosingtest persons.

Relevant data on the test personsand their medical history were collec-ted using a questionnaire before anymeasurement took place. An examina-tion to identify abnormal gait patternsand malpositioning of the feet, hipand knee joints was conducted foreach subject. In addition, the range ofmotion of the upper and lower anklejoint was determined according to theneutral-zero method. Subjects withnotable limitations of movement orpathological abnormalities were exclu-ded from measurement. Subjects gavetheir written consent before participa-ting in this study.

Shoe Conditions

In this study, two different shoe con-ditions were analysed for the rightfoot. On their left foot, participantswore a neutral shoe with height com-pensation (Adidas Samba; Adidas AG,Germany). Height compensation wasmodified in each case to match shoeheight for each individual shoe condi-tion and shoe size.

In this study, the offloading shoesRelief Dual (DARCO International Inc.,Huntington, USA) (see Figure 1) and apostoperative shoe from a competitorwere compared.

For more information about thecompetitor shoe please contact theauthor.

Both shoes were offloading shoes.The competitor shoe is indexed in theGerman register of medical technical

2 vebitoSCIENCE mea-

suring sole with five

sensor positions

(distal interphalan-

geal joints I and V,

metatarsophalan-

geal joints I and V

and processus

calcaneus).

1 The offloading shoe Relief Dual (DARCO

International Inc., Huntington, USA)

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32 foot & shoe 1/2016

and torsional moments was conductedonce per shoe condition. For each trial, 30 gait cycles were recorded.

Data processing and evaluation

The curves of bending and torsionalmoments were recorded at five different measuring points by the vebitoSCIENCE measuring system. Theload curves of 30 serial gait cycles(GC) were monitored and mean valueswere calculated. The point of reference determined automatically by the soft-ware was heel strike [3]. Before ana -lysis, the raw data were run throughlow-pass filter (Butterworth, 10 Hz,second order).

The curves of the bending and tor-sional moments of the right foot wereanalyzed for all five measuring points.

Besides these load curves, five ad-ditional parameters were statisticallyanalysed:– maximum plantar flexion moment/

Nmm– maximum dorsal extension moment/

Nmm– range of bending moments/ Nmm– alternating load of bending mo-

ments/ %– momentum (absolute value) of ben-

ding moments/ Nmm * %Figure 3 presents a characteristic

bending moment curve, including theanalysed parameters. The parameterrange is an index of the range of moti-on over an entire gait cycle. The mo-mentum (absolute value) has not beenvisualised. In this study, the term mo-mentum (absolute value) is used to re-fer to the absolute value of the ben-ding momentum. This designation isabstracted and not equivalent to thephysical quantity momentum. The loadover the entire gait cycle can be cha-racterized by considering the parame-

S C I E N C E

ter momentum (absolute value) of thebending moments.

If there are no moments in the di-rection of a plantar flexion, the mini-mum of the dorsal extension momentsis shown. The alternating load (AL) iscalculated as shown in formula (1). Ifthere is no plantar flexion or dorsal ex-tension moment, then there is no al-ternating load, either.

A two-sided paired t-test was con-ducted to detect significant differen-ces (p < 0.05).

ResultsCurves

The continuous curves present the me-an values, the dotted curves presentthe standard deviation (SD) . The bluecurves describe the loading in the Re-lief Dual shoe as a function of the GCand the red curves the loading in thecompetitor shoe. For each graph, thenumber of subjects (N) used to calcu-late the mean value is given.

If there were measurement errorswith regards to individual test per-sons, then N < 22.

Bending momentsThe mean bending moment at the heelproduces a similar curve in both shoeconditions, with a small SD. The curvesfirst show a dorsal extension momentwith a local peak at about 10 – 20%gait cycle, followed by a slow decreasethat reaches zero at about 60 – 70%GC. The measurement for the ReliefDual shows a slightly higher dorsal ex-tension moment and an additionalplantar flexion moment (Figure 4).

Starting from about 40% GC, ben-ding moments at measuring point MTPI show very similar curves with small

SDs, whereas the competitor presentsconsiderably higher dorsal extensionmoments. After heel strike until about45 % GC, a slight plantar flexion mo-ment can be observed in the ReliefDual. By contrast, the competitor pre-sents a dorsal extension moment.

At measuring point MTP V, the ben-ding moment curves differ little andpresent small SDs. After heel strike, alocal maximum occurs at about 10 –20% GC. At 30 – 40% GC, a local mini-mum can be observed. At about 60%GC, a conspicuous local maximum oc-curs, afterwards showing a steepdecrease. The dorsal extension mo-ments of the Relief Dual also have con-siderably lower values in comparisonto the competitor at this measuringpoint. There is no plantar flexion mo-ment for either shoe condition at mea-suring point MTP V.

Both mean bending moment curvesare almost identical at measuringpoint DIP I. There is a local maximumat about 60 – 70% GC. A relativelyhigh SD exists in the first phase of thegait cycle (until approx. 50%). Afterthe local maximum is reached, bothcurves show a steep decrease. At thismeasuring point, both shoe conditionsdisplay a dominant dorsal extensionmoment.

At DIP V, the bending moments ofboth shoe conditions present a similarcurve. The high SDs apparent here aredue to the relatively high variationsbetween individual subjects. Bendingmoments change their direction from aplantar flexion moment to a dorsal ex-tension moment earlier for the compe-titor (at approx. 55 % GC) as comparedto the Relief Dual. Dorsal extensionvalues are slightly smaller for the com-petitor than for the Relief Dual.

Torsional moments

The mean torsional moment at theheel demonstrates a strongly varyingcurve with a large SD under both shoeconditions. The measurement taken forthe Relief Dual shows a higher eversi-on moment as compared to the com-petitor. An inversion moment is domi-nant in the competitor shoe. High SDsindicate strong variations in the curves of the individual test persons(Figure 4).

The mean torsional moments de-monstrate a similar curve, but unlikethe bending moments at MTP I, higherSDs occur at this location. In addition,

3 Exemplary curve progression for bending moments including illustration of analysed parameters.

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33

foot & shoe 1/2016

4 Mean bending and

torsional moments on

five sensor regions.

Continuous lines pre-

sent the mean values,

dotted lines present

the standard deviation.

Positive values descri-

be a dorsal extension

moment (internal rota-

tion with regard to the

central axis of the foot),

negative values a plan-

tar flexion moment

(external rotation).

S C I E N C E

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S C I E N C E

34 foot & shoe 1/2016

with regards to torsional moments atDIP I. The variance is discernibly high,especially for the Relief Dual. Momentsin the direction of an eversion are do-minant for both shoe conditions.

Under both shoe conditions, thecurves for torsional moments at mea-suring point DIP V show highly oppo-site trends (Fig. 4). In the curve forthe Relief Dual, an eversion moment isdominant, whereas the competitorshoe generally demonstrates an inver-sion moment. This inversion momentis considerably higher in comparisonto the corresponding values of the Re-lief Dual.

Comparison

of selected measuring parameters

Table 1 present the findings for theselected measuring parameters of the

bending and torsional measurement.To enable a direct comparison of theanalysed shoe conditions, the calcula-ted mean values of the measuring parameters are listed below. Signifi-cant differences between both shoeconditions are highlighted in grey(see Table 1).

For the Relief Dual, a significantlyhigher plantar flexion moment can beobserved at the heel and MTP I ascompared to the competitor. At theother measuring points, there is nosignificant difference in the plantarflexion moments.

At MTP I and MTP V, the mean va-lues of the maximum dorsal extensionmoments of the competitor are signifi-cantly higher as compared to the Reli-ef Dual. At the other measuring points,no significant difference exists for thedorsal extension moments.

Only at measuring point MTP V isthere a significant difference betweenthe two shoe conditions for the range.Here, the value of the competitor issignificantly higher than that of theRelief Dual. At the other measuringpoints, there is no significant differen-ce between the two shoe conditions.

The alternating load value of theRelief Dual is significantly higher thanthe value of the competitor at themeasuring points heel, MTP I and DIPI. Because there is no plantar flexionmoment, no alternating load can bedetermined at measuring point MTP V.At DIP V, no significant difference canbe observed between the two shoeconditions.

At the measuring points MTP I andMTP V, the momentum value of thecompetitor is significantly higher thanthe value of the Relief Dual. There wasno significant difference as regardsthe other measuring points.

DiscussionsThe aim of this study was to evaluateloads acting on the foot during wal-king in two different offloading shoeswith very different shoe designs. TheRelief Dual was compared to an off -loading shoe that already is indexed in the German register of medical technical aids. The analysis focuses onfunctional limitation and relief of the forefoot. Bending and torsional loads were measured using the vebitoSCIENCE measuring system.

The curves of the bending loads atthe different measuring points are sig-

the eversion and inversion momentsare higher in the competitor shoe thanin the Relief Dual.

For both shoe conditions, only aninversion moment can be observedwith regards to the torsional momentsat MTP V. The curves are quite similarand there is a small SD. The increase inand amplitude of the inversion mo-ment are considerably higher for thecompetitor in comparison to the Reli-ef Dual.

In contrast to the bending mo-ments, more differences are found re-garding the curves of the torsionalmoments at DIP I. In the first phase ofthe gait cycle, there is a greater in-crease and higher values are observedfor the torsional moments of the Reli-ef Dual as compared to the competitor.Relatively high SDs can be observed

Table 1 Results of the five compared measuring parameters and the findings of the conducted

t-test. Mean value and standard deviation (N=22) presented for each parameter for the Relief Dual

and the competitor at all measuring points.

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35foot & shoe 1/2016

The competitor presents a smaller ma-ximum plantar flexion moment and analternating load at MTP I.

At measuring points DIP I and DIPV, the competitor achieves greater re-lief of the forefoot for one of ten va-lues (alternating load at DIP I). For allother parameters, both offloadingshoes achieve similar functional limi-tation and relief of the forefoot at the-se measuring points.

Because of the additional plantarflexion moments of the Relief Dual andthe lower alternating loads of thecompetitor, the competitor achievedcomparatively slightly reduced loadsat the forefoot. However, given thatthe values of the maximum dorsal ex-tension moment and the momentum(absolute value) of the Relief Dual aresignificantly smaller than the values ofthe competitor, it can be assumed thatthe Relief Dual achieves similar reliefof the forefoot, and in some caseseven greater relief.

Individual walking speed was cho-sen by each participant during thefirst measuring condition and remai-ned constant for the second condition.For statistical analysis, a paired t-testinsensitive to the effect of interindivi-dual differences in walking speed wasused.

For the very same reason, differen-ces in sole stiffness caused by diffe-rent shoe sizes do not affect the dataanalysis; the shoe sizes differed fromsubject to subject, but remained con-stant for the two testing conditions.

To derive more information on theoffloading effects of the two differentshoe designs, the plantar pressure dis-tribution should be analyzed as well.It is also important to what extent pa-tients feel familiar with the shoes andhow the orthopedic device influencesnormal gait patterns. Furthermore, tosee how offloading shoes influencethe gait patterns of bending and tor-sional stress acting on the foot, addi-tional data should be analyzed, i.e.from the left foot wearing the controlshoe, or under control conditions. Todate, no information has been publis-hed on the influences of bending andtorsional loads on the feet of surgerypatients wearing offloading shoes.

ConclusionsAlthough the two shoes investigatedhad very different designs, there wereonly minor differences observed bet-

ween the bending and torsional stressacting on the foot in each shoe de-sign. That said, the offloading effectsduring walking measured by multidi-mensional parameters were attributa-ble to demonstrable differences inbending and torsional stress under thetwo shoe conditions. The significantdifferences found for MTP I and MTP Vsuggest that the Relief Dual has aslightly greater offloading effect onthe forefoot. After this study was com-pleted, the Relief Dual was indexed inthe German register of medical technical aids as an offloading shoe. However, to provide a more compre-hensive view of stress acting on thefoot, plantar pressure must be ana -lyzed in combination with bendingand torsional stress measurements infuture studies.

Conflict of interest

This study was supported by DARCO (Europe)GmbH. This funding did not influence studydesign, data analyses and conclusions.

Literature

[1] Arndt A, Ekenman I, Westblad P, Lund-berg A. Effects of fatigue and load varia-tion on metatarsal deformation measuredin vivo during barefoot walking. Journalof Biomechanics. 2002; 35, 621–8, doi10.1016/S0021-9290(01)00241-X.

[2] Caravaggi P, Giangrande A, Berti L, Lulli-ni G, Leardini A. Pedobraographic and ki-netic analysis in the functional evaluati-on of two post-operative forefoot offloa-ding shoes. Journal of Foot and AnkleResearch. 2015, 8:59, doi10.1186/s13047-015-0116-3.

[3] Dawin N, Kerkhoff A, Peikenkamp K. Ben-ding and Torsional Moments – A newmeasuring system for gait analysis.Scientific talk on: TAR 2015: TechnicallyAssisted Rehabilitation Conference, Ber-lin, March 12 to 13, 2015. Online:http://www.ige.tu-berlin.de/fileadmin/fg176/IGE_Printrei-he/TAR_2015/Session_order/Session_5_Event_1_paper_Dawin_Nora_.pdf

[4] Dawin N, Stief T, Peikenkamp K. Innen-sohlenmesssystem zur Bestimmung vonBiege- und Torsionsmomenten im Schuh.Orthopädieschuhtechnik – Medizin undTechnik. 2013; 34–6.

[5] Stief T, Peikenkamp K. A new insole mea-surement system to detect bending andtorsional moments at the human foot during footwear condition: A technicalreport. J Foot Ankle Res. 2015; 8, 1886,doi 10.1186/s13047-015-0105-6.

nificant and will be discussed as follo-ws. The findings of the bending andtorsional measurements show that si-milar levels of functional stress occurunder the two shoe conditions analy-sed. However, the Relief Dual offeredthe advantage of a reduced dorsal ex-tension moment at MTP I and MTP V.The differences between the two shoeconditions especially occur at themeasuring points heel, MTP I and MTPV. At DIP I and DIP V, the load curvesof both shoes are similar. For the Reli-ef Dual, an additional slight plantarflexion moment can be observed at theheel. Furthermore, the dorsal extensi-on moment is slightly higher at thismeasuring point. The bending load atthe heel is of subordinate importanceregarding the question of functionallimitation and relief of the forefoot. Atthese two measuring points, the dorsalextension moment of the Relief Dual isnotably lower than that of the compe-titor. This implies greater functionallimitation and increased relief of theforefoot. The pronounced occurrenceof a plantar flexion moment at MTP I isof lower importance as compared tothe reduced dorsal extension moment,because the highest loads at the fore-foot are observed during terminalstance and can therefore be expressedwell by the dorsal extension moment.At measuring point MTP V, only a redu-ced dorsal extension moment can beobserved. The fact that no additionalplantar flexion moment was observedimplies that the Relief Dual providesbetter offloading of the forefoot.

Interpreting torsional load curvesgenerally only allows conclusions to bedrawn on the gait pattern of individu-al test persons. They also complicateinterpretation of the occurring loads.

Due to their lack of relevance tooffloading the forefoot, the heel para-meters will not be discussed any furt-her. At measuring points MTP I andMTP V, seven of the nine load parame-ters selected differ significantly. Forfive of these selected parameters, theRelief Dual demonstrates greater reliefof the forefoot during walking. For twoof these parameters, the competitorachieves smaller loads at the forefoot.The values of the maximum dorsal ex-tension moment at MTP I and MTP V, ofthe range at MTP V and of the momen-tum (absolute value) at MTP I and MTPV are significantly smaller for the Reli-ef Dual as compared to the competitor.

S C I E N C E

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30 foot & shoe 1/2016

Specialized orthopedic devices forstabilizing and offloading thefoot are often used to support the

rehabilitation process after foot sur-gery [2]. There are different types ofshoes prescribed after surgery, such asthose specialized for wound manage-ment or with offloading functions. InGermany, these therapeutic shoesmust meet essential requirements toreceive an official number in the German register of medical technicalaids and it is therefore necessary totest their quality and functions. Wound management requires antibac-terial material and postoperativeshoes have to be firmly affixed to thefoot to reduce loading in the forefootarea. Postoperative shoes must also becomfortable, even if the foot is banda-ged. Forefoot offloading shoes areused when load has to be taken off theinjured area but the patient needs tostay mobile, for example, after halluxvalgus surgery.

How much the injured area is off -loaded can generally be justified bymeasuring plantar pressure. In additi-on to plantar pressure, however, mult-idimensional stresses like bending andtorsional moments also act on thefoot.

After aggregating their calibrationresults, they concluded that the insolemeasuring system is able to easily andreliably measure bending and torsionalmoments at the forefoot [5].

This study analysed the effects oftwo different offloading shoes on ben-ding and torsional moments at the fo-refoot: the Relief Dual offloading shoe(Darco Europe GmbH, Raisting, Ger-many) and a competitor post-op shoe.Both are postoperative offloadingshoes, but their designs are very diffe-rent. The competitor shoe is indexedin the German register of medicaltechnical aids, which is a preconditionfor the reimbursement through thehealth insurance. The aim of the studywas to investigate whether the mecha-nical conditions present in the twoshoes have comparable or significantlydifferent influences on stress at theforefoot.

The insole measuring system vebi-toSCIENCE (vebitosolution GmbH,Steinfurt, Germany) was used to moni-tor bending and torsional stress. Thissystem uses 5 parameters to measure ashoe’s functional limitation and fore-foot offloading effect.

22 healthy subjects (mean age: 35years; 9 female, 13 male) participatedin the present study. Loading curvesfor 30 consecutive gait cycles were ac-quired from each test person, afterwhich the mean values were calcula-ted. The curve of bending and torsio-nal moments were measured at fivedifferent sensor positions and parame-ters like maxima, range and alterna-

Analysis of Bending and Torsional Stresson the Foot in Different Offloading Shoes

Original Research Report

Nora Dawin, M.Sc.1,2; Nicole Dirksen, M.Sc.2; Philipp Buss, M.Sc.2; Klaus Peikenkamp, Prof. Dr. habil.2

Abstract

This study compares the bending and torsional stress acting on the foot in the Darco Relief Dual offloading shoe to that of an al-

ready licensed competitor. Levels of functional limitation and forefoot offloading were analysed in 22 healthy subjects

(9f, 13m; 35 ± 8y) using the vebitoSCIENCE measuring system. 30 gait cycles were monitored and the mean values calculated for

selected parameters. The Darco Relief Dual significantly reduced (p<0.05) maximum dorsal extension moments at MTP I and V. The-

re was also a significant reduction in the range of motion at MTP V and a significant decrease in the total load on MTP I and V over

the entire gait cycle. In the competitor shoe, a significantly reduced maximum plantar flexion moment and alternating load were

measured at MTP I and DIP I.

Keywords: Bending moment, torsional moment, stress, offloading shoes

Bending moments, which are calcu-lated by multiplying the acting forceby the respective lever arm, causebending deformations in the shoe; orrather, on the foot in the shoe. If, forinstance, the forefoot is extended dor-sally with respect to the hindfoot, the-re is an acting dorsal extension mo-ment. In the case of a cyclical move-ment like walking, alternating loadingoccurs in the form of both dorsal extension and plantar flexion moment.Alter nating load cannot be detectedby conventional pressure measurementsystems [5].

The first findings on bending loadsacting on the foot were published byArndt et al. (2002) [1]. The authorsconducted an in-vivo study in whichstrain gauges were surgically implan-ted into the second dorsal metatarsalbone. These measured strain on the2nd metatarsal head during walkingand were capable of detecting bothtensional stress and compressionstress. In the past, invasive procedu-res such as this were the only way tomeasure bending and torsional stres-ses acting on the foot in shoes. Howe-ver, a new, non-invasive insole measu-rement system, developed at the Bio-mechanics Research Laboratory atMünster University of Applied Sciences(Germany), is now available.

Stief and Peikenkamp presented thefirst results obtained with the new in-sole measuring system in 2015, de-monstrating that it could detect plan-tarflexion stress followed by dorsiflexi-on stress during each gait cycle [4, 5].

S C I E N C E

1 vebitosolution GmbH

Am Campus 2

48565 Steinfurt, Germany2 Fachhochschule Münster

Labor für Biomechanik

Am Bürgerkamp 3

48565 Steinfurt, Germany

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31foot & shoe 1/2016

The measuring insoles were placedin the shoes and cables were affixed tothe participants’ legs with flexibleVelcro® straps. To avoid distorted re-sults due to fatigue or testing order,the order of shoe conditions testedwas randomized. Subjects wore thedifferent test shoes on their right foot.On their left foot, they wore an AdidasSamba with additional height compen-sation matching that of the offloadingshoe being tested. The measuring in-soles were worn on both feet. The sy-stem requires an initially unloadedstate, which was measured with sub-jects sitting on a raised chair with legsand feet hanging and immobile. Themeasurements were taken on a Sprin-tex slat belt treadmill (SPRINTEX Trai-ningsgeräte GmbH, Kleines Wiesental,Germany).

Before data acquisition, partici-pants were given five minutes of fami-liarization per shoe condition, duringwhich they walked on the treadmill ata self-selected speed (minimum of 2.5km/h). The velocity chosen by thesubject during this period of fami-liarization was maintained for the fol-lowing trials. Measurement of bending

aids, which is a precondition forthe reimbursement through thehealth insurance (medical tech -nical aids classification numbergroup: 31.03.03.). The Darco Re-lief Dual did not have an medicaltechnical aids classification num-ber at the beginning of this stu-dy. The offloading shoes are verydifferent in design. The competitoris a closed model with cushioned in-terior, featuring a rigid, full outsolewith a double-rocker. The Relief Dual isan open shoe, which protects the toes,with an extended outsole. The outsoleis made of two different materials witha continuous, rigid stiffening sole.Both shoes are fastened to the footwith Velcro.

In total, seven shoe sizes of the Re-lief Dual (34 female – 48 male) and fi-ve sizes of the competitor (37 – 46)were compared. Heel heights of thecompetitor shoes ranged from 30 – 32mm and the Relief Dual from 31 – 39mm.

Bending and torsional

insole measurements

The vebitoSCIENCE insole measure-ment system described above was usedto measure bending and torsionalstress (5 sensor positions, 125 Hz, 16 bit).

The vebitoSCIENCE measurementsystem was developed by the Bio -mechanics Research Laboratory, Mün-ster University of Applied Sciences, Germany. Strain gauges are fixed to a specially shaped flexible layer in theinsoles. The purpose of the specialshaping is to detect bending and tor-sional loads independent of the medi-al and lateral forefoot. Mirror-invertedand interconnected strain gauges canbe found on both the upper and bot-tom surface. The interconnection ofthe strain gauges into half bridge cir-cuits for bending and full bridge cir-cuits for torsion allows both loads tobe measured at the same time. Themeasuring frequency is 125 Hz. Sen-sors are placed proximal to metatarso-phalangeal joints I and V (MTP I andV), proximal to the distal interphalan-geal joints I and V (DIP I and DIP V)and distal to the processus calca -neus(see Figure 2). Data are trans -ferred wirelessly to a notebook viaBluetooth. The calibration results pre-sented a coefficient of determinationof R² > 0.999 and a linearity factor ofalmost 1.0 [5].

S C I E N C E

ting stress were analysed statistically.

MethodsParticipants

The loads occurring under the diffe-rent shoe conditions were recorded intrials with 22 test persons (mean age:35 ± 8 years, between 25 and 52). Ni-ne of the 22 subjects were female. Ageand normal, physiological gait patternwere the selection factors for choosingtest persons.

Relevant data on the test personsand their medical history were collec-ted using a questionnaire before anymeasurement took place. An examina-tion to identify abnormal gait patternsand malpositioning of the feet, hipand knee joints was conducted foreach subject. In addition, the range ofmotion of the upper and lower anklejoint was determined according to theneutral-zero method. Subjects withnotable limitations of movement orpathological abnormalities were exclu-ded from measurement. Subjects gavetheir written consent before participa-ting in this study.

Shoe Conditions

In this study, two different shoe con-ditions were analysed for the rightfoot. On their left foot, participantswore a neutral shoe with height com-pensation (Adidas Samba; Adidas AG,Germany). Height compensation wasmodified in each case to match shoeheight for each individual shoe condi-tion and shoe size.

In this study, the offloading shoesRelief Dual (DARCO International Inc.,Huntington, USA) (see Figure 1) and apostoperative shoe from a competitorwere compared.

For more information about thecompetitor shoe please contact theauthor.

Both shoes were offloading shoes.The competitor shoe is indexed in theGerman register of medical technical

2 vebitoSCIENCE mea-

suring sole with five

sensor positions

(distal interphalan-

geal joints I and V,

metatarsophalan-

geal joints I and V

and processus

calcaneus).

1 The offloading shoe Relief Dual (DARCO

International Inc., Huntington, USA)

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32 foot & shoe 1/2016

and torsional moments was conductedonce per shoe condition. For each trial, 30 gait cycles were recorded.

Data processing and evaluation

The curves of bending and torsionalmoments were recorded at five different measuring points by the vebitoSCIENCE measuring system. Theload curves of 30 serial gait cycles(GC) were monitored and mean valueswere calculated. The point of reference determined automatically by the soft-ware was heel strike [3]. Before ana -lysis, the raw data were run throughlow-pass filter (Butterworth, 10 Hz,second order).

The curves of the bending and tor-sional moments of the right foot wereanalyzed for all five measuring points.

Besides these load curves, five ad-ditional parameters were statisticallyanalysed:– maximum plantar flexion moment/

Nmm– maximum dorsal extension moment/

Nmm– range of bending moments/ Nmm– alternating load of bending mo-

ments/ %– momentum (absolute value) of ben-

ding moments/ Nmm * %Figure 3 presents a characteristic

bending moment curve, including theanalysed parameters. The parameterrange is an index of the range of moti-on over an entire gait cycle. The mo-mentum (absolute value) has not beenvisualised. In this study, the term mo-mentum (absolute value) is used to re-fer to the absolute value of the ben-ding momentum. This designation isabstracted and not equivalent to thephysical quantity momentum. The loadover the entire gait cycle can be cha-racterized by considering the parame-

S C I E N C E

ter momentum (absolute value) of thebending moments.

If there are no moments in the di-rection of a plantar flexion, the mini-mum of the dorsal extension momentsis shown. The alternating load (AL) iscalculated as shown in formula (1). Ifthere is no plantar flexion or dorsal ex-tension moment, then there is no al-ternating load, either.

A two-sided paired t-test was con-ducted to detect significant differen-ces (p < 0.05).

ResultsCurves

The continuous curves present the me-an values, the dotted curves presentthe standard deviation (SD) . The bluecurves describe the loading in the Re-lief Dual shoe as a function of the GCand the red curves the loading in thecompetitor shoe. For each graph, thenumber of subjects (N) used to calcu-late the mean value is given.

If there were measurement errorswith regards to individual test per-sons, then N < 22.

Bending momentsThe mean bending moment at the heelproduces a similar curve in both shoeconditions, with a small SD. The curvesfirst show a dorsal extension momentwith a local peak at about 10 – 20%gait cycle, followed by a slow decreasethat reaches zero at about 60 – 70%GC. The measurement for the ReliefDual shows a slightly higher dorsal ex-tension moment and an additionalplantar flexion moment (Figure 4).

Starting from about 40% GC, ben-ding moments at measuring point MTPI show very similar curves with small

SDs, whereas the competitor presentsconsiderably higher dorsal extensionmoments. After heel strike until about45 % GC, a slight plantar flexion mo-ment can be observed in the ReliefDual. By contrast, the competitor pre-sents a dorsal extension moment.

At measuring point MTP V, the ben-ding moment curves differ little andpresent small SDs. After heel strike, alocal maximum occurs at about 10 –20% GC. At 30 – 40% GC, a local mini-mum can be observed. At about 60%GC, a conspicuous local maximum oc-curs, afterwards showing a steepdecrease. The dorsal extension mo-ments of the Relief Dual also have con-siderably lower values in comparisonto the competitor at this measuringpoint. There is no plantar flexion mo-ment for either shoe condition at mea-suring point MTP V.

Both mean bending moment curvesare almost identical at measuringpoint DIP I. There is a local maximumat about 60 – 70% GC. A relativelyhigh SD exists in the first phase of thegait cycle (until approx. 50%). Afterthe local maximum is reached, bothcurves show a steep decrease. At thismeasuring point, both shoe conditionsdisplay a dominant dorsal extensionmoment.

At DIP V, the bending moments ofboth shoe conditions present a similarcurve. The high SDs apparent here aredue to the relatively high variationsbetween individual subjects. Bendingmoments change their direction from aplantar flexion moment to a dorsal ex-tension moment earlier for the compe-titor (at approx. 55 % GC) as comparedto the Relief Dual. Dorsal extensionvalues are slightly smaller for the com-petitor than for the Relief Dual.

Torsional moments

The mean torsional moment at theheel demonstrates a strongly varyingcurve with a large SD under both shoeconditions. The measurement taken forthe Relief Dual shows a higher eversi-on moment as compared to the com-petitor. An inversion moment is domi-nant in the competitor shoe. High SDsindicate strong variations in the curves of the individual test persons(Figure 4).

The mean torsional moments de-monstrate a similar curve, but unlikethe bending moments at MTP I, higherSDs occur at this location. In addition,

3 Exemplary curve progression for bending moments including illustration of analysed parameters.

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33

foot & shoe 1/2016

4 Mean bending and

torsional moments on

five sensor regions.

Continuous lines pre-

sent the mean values,

dotted lines present

the standard deviation.

Positive values descri-

be a dorsal extension

moment (internal rota-

tion with regard to the

central axis of the foot),

negative values a plan-

tar flexion moment

(external rotation).

S C I E N C E

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S C I E N C E

34 foot & shoe 1/2016

with regards to torsional moments atDIP I. The variance is discernibly high,especially for the Relief Dual. Momentsin the direction of an eversion are do-minant for both shoe conditions.

Under both shoe conditions, thecurves for torsional moments at mea-suring point DIP V show highly oppo-site trends (Fig. 4). In the curve forthe Relief Dual, an eversion moment isdominant, whereas the competitorshoe generally demonstrates an inver-sion moment. This inversion momentis considerably higher in comparisonto the corresponding values of the Re-lief Dual.

Comparison

of selected measuring parameters

Table 1 present the findings for theselected measuring parameters of the

bending and torsional measurement.To enable a direct comparison of theanalysed shoe conditions, the calcula-ted mean values of the measuring parameters are listed below. Signifi-cant differences between both shoeconditions are highlighted in grey(see Table 1).

For the Relief Dual, a significantlyhigher plantar flexion moment can beobserved at the heel and MTP I ascompared to the competitor. At theother measuring points, there is nosignificant difference in the plantarflexion moments.

At MTP I and MTP V, the mean va-lues of the maximum dorsal extensionmoments of the competitor are signifi-cantly higher as compared to the Reli-ef Dual. At the other measuring points,no significant difference exists for thedorsal extension moments.

Only at measuring point MTP V isthere a significant difference betweenthe two shoe conditions for the range.Here, the value of the competitor issignificantly higher than that of theRelief Dual. At the other measuringpoints, there is no significant differen-ce between the two shoe conditions.

The alternating load value of theRelief Dual is significantly higher thanthe value of the competitor at themeasuring points heel, MTP I and DIPI. Because there is no plantar flexionmoment, no alternating load can bedetermined at measuring point MTP V.At DIP V, no significant difference canbe observed between the two shoeconditions.

At the measuring points MTP I andMTP V, the momentum value of thecompetitor is significantly higher thanthe value of the Relief Dual. There wasno significant difference as regardsthe other measuring points.

DiscussionsThe aim of this study was to evaluateloads acting on the foot during wal-king in two different offloading shoeswith very different shoe designs. TheRelief Dual was compared to an off -loading shoe that already is indexed in the German register of medical technical aids. The analysis focuses onfunctional limitation and relief of the forefoot. Bending and torsional loads were measured using the vebitoSCIENCE measuring system.

The curves of the bending loads atthe different measuring points are sig-

the eversion and inversion momentsare higher in the competitor shoe thanin the Relief Dual.

For both shoe conditions, only aninversion moment can be observedwith regards to the torsional momentsat MTP V. The curves are quite similarand there is a small SD. The increase inand amplitude of the inversion mo-ment are considerably higher for thecompetitor in comparison to the Reli-ef Dual.

In contrast to the bending mo-ments, more differences are found re-garding the curves of the torsionalmoments at DIP I. In the first phase ofthe gait cycle, there is a greater in-crease and higher values are observedfor the torsional moments of the Reli-ef Dual as compared to the competitor.Relatively high SDs can be observed

Table 1 Results of the five compared measuring parameters and the findings of the conducted

t-test. Mean value and standard deviation (N=22) presented for each parameter for the Relief Dual

and the competitor at all measuring points.

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35foot & shoe 1/2016

The competitor presents a smaller ma-ximum plantar flexion moment and analternating load at MTP I.

At measuring points DIP I and DIPV, the competitor achieves greater re-lief of the forefoot for one of ten va-lues (alternating load at DIP I). For allother parameters, both offloadingshoes achieve similar functional limi-tation and relief of the forefoot at the-se measuring points.

Because of the additional plantarflexion moments of the Relief Dual andthe lower alternating loads of thecompetitor, the competitor achievedcomparatively slightly reduced loadsat the forefoot. However, given thatthe values of the maximum dorsal ex-tension moment and the momentum(absolute value) of the Relief Dual aresignificantly smaller than the values ofthe competitor, it can be assumed thatthe Relief Dual achieves similar reliefof the forefoot, and in some caseseven greater relief.

Individual walking speed was cho-sen by each participant during thefirst measuring condition and remai-ned constant for the second condition.For statistical analysis, a paired t-testinsensitive to the effect of interindivi-dual differences in walking speed wasused.

For the very same reason, differen-ces in sole stiffness caused by diffe-rent shoe sizes do not affect the dataanalysis; the shoe sizes differed fromsubject to subject, but remained con-stant for the two testing conditions.

To derive more information on theoffloading effects of the two differentshoe designs, the plantar pressure dis-tribution should be analyzed as well.It is also important to what extent pa-tients feel familiar with the shoes andhow the orthopedic device influencesnormal gait patterns. Furthermore, tosee how offloading shoes influencethe gait patterns of bending and tor-sional stress acting on the foot, addi-tional data should be analyzed, i.e.from the left foot wearing the controlshoe, or under control conditions. Todate, no information has been publis-hed on the influences of bending andtorsional loads on the feet of surgerypatients wearing offloading shoes.

ConclusionsAlthough the two shoes investigatedhad very different designs, there wereonly minor differences observed bet-

ween the bending and torsional stressacting on the foot in each shoe de-sign. That said, the offloading effectsduring walking measured by multidi-mensional parameters were attributa-ble to demonstrable differences inbending and torsional stress under thetwo shoe conditions. The significantdifferences found for MTP I and MTP Vsuggest that the Relief Dual has aslightly greater offloading effect onthe forefoot. After this study was com-pleted, the Relief Dual was indexed inthe German register of medical technical aids as an offloading shoe. However, to provide a more compre-hensive view of stress acting on thefoot, plantar pressure must be ana -lyzed in combination with bendingand torsional stress measurements infuture studies.

Conflict of interest

This study was supported by DARCO (Europe)GmbH. This funding did not influence studydesign, data analyses and conclusions.

Literature

[1] Arndt A, Ekenman I, Westblad P, Lund-berg A. Effects of fatigue and load varia-tion on metatarsal deformation measuredin vivo during barefoot walking. Journalof Biomechanics. 2002; 35, 621–8, doi10.1016/S0021-9290(01)00241-X.

[2] Caravaggi P, Giangrande A, Berti L, Lulli-ni G, Leardini A. Pedobraographic and ki-netic analysis in the functional evaluati-on of two post-operative forefoot offloa-ding shoes. Journal of Foot and AnkleResearch. 2015, 8:59, doi10.1186/s13047-015-0116-3.

[3] Dawin N, Kerkhoff A, Peikenkamp K. Ben-ding and Torsional Moments – A newmeasuring system for gait analysis.Scientific talk on: TAR 2015: TechnicallyAssisted Rehabilitation Conference, Ber-lin, March 12 to 13, 2015. Online:http://www.ige.tu-berlin.de/fileadmin/fg176/IGE_Printrei-he/TAR_2015/Session_order/Session_5_Event_1_paper_Dawin_Nora_.pdf

[4] Dawin N, Stief T, Peikenkamp K. Innen-sohlenmesssystem zur Bestimmung vonBiege- und Torsionsmomenten im Schuh.Orthopädieschuhtechnik – Medizin undTechnik. 2013; 34–6.

[5] Stief T, Peikenkamp K. A new insole mea-surement system to detect bending andtorsional moments at the human foot during footwear condition: A technicalreport. J Foot Ankle Res. 2015; 8, 1886,doi 10.1186/s13047-015-0105-6.

nificant and will be discussed as follo-ws. The findings of the bending andtorsional measurements show that si-milar levels of functional stress occurunder the two shoe conditions analy-sed. However, the Relief Dual offeredthe advantage of a reduced dorsal ex-tension moment at MTP I and MTP V.The differences between the two shoeconditions especially occur at themeasuring points heel, MTP I and MTPV. At DIP I and DIP V, the load curvesof both shoes are similar. For the Reli-ef Dual, an additional slight plantarflexion moment can be observed at theheel. Furthermore, the dorsal extensi-on moment is slightly higher at thismeasuring point. The bending load atthe heel is of subordinate importanceregarding the question of functionallimitation and relief of the forefoot. Atthese two measuring points, the dorsalextension moment of the Relief Dual isnotably lower than that of the compe-titor. This implies greater functionallimitation and increased relief of theforefoot. The pronounced occurrenceof a plantar flexion moment at MTP I isof lower importance as compared tothe reduced dorsal extension moment,because the highest loads at the fore-foot are observed during terminalstance and can therefore be expressedwell by the dorsal extension moment.At measuring point MTP V, only a redu-ced dorsal extension moment can beobserved. The fact that no additionalplantar flexion moment was observedimplies that the Relief Dual providesbetter offloading of the forefoot.

Interpreting torsional load curvesgenerally only allows conclusions to bedrawn on the gait pattern of individu-al test persons. They also complicateinterpretation of the occurring loads.

Due to their lack of relevance tooffloading the forefoot, the heel para-meters will not be discussed any furt-her. At measuring points MTP I andMTP V, seven of the nine load parame-ters selected differ significantly. Forfive of these selected parameters, theRelief Dual demonstrates greater reliefof the forefoot during walking. For twoof these parameters, the competitorachieves smaller loads at the forefoot.The values of the maximum dorsal ex-tension moment at MTP I and MTP V, ofthe range at MTP V and of the momen-tum (absolute value) at MTP I and MTPV are significantly smaller for the Reli-ef Dual as compared to the competitor.

S C I E N C E

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