Unit 4 Prosthesis

7/28/2019 Unit 4 Prosthesis

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UNIT 4


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Syllabus

PROSTHETIC AND ORTHOTIC DEVICES

Hand and arm replacement different types

of models, externally powered limb

prosthesis, feedback in orthotic system,

functional electrical stimulation, sensory assist

devices.


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Amputation

Amputation is theintentional surgicalremoval of a limb orbody part or thetraumatic loss of a limb.

As a surgical measure,it is used to control painor a disease process inthe affected limb, suchas malignancy organgrene.

In some cases, it iscarried out onindividuals as apreventative surgery forsuch problems.


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Types of amputation

leg

amputation of digits

partial foot amputation

ankle disarticulation

below-knee amputation(transtibial)

knee-bearing amputation(knee disarticulation)

above knee amputation(transfemoral)

Van-ness rotation

hip disarticulation

arm

amputation of digits

metacarpal amputation

wrist disarticulation

forearm amputation(transradial)

elbow disarticulation

above-elbow amputation(transhumeral)


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Reasons for amputation

Amputation isperformed for thefollowing reasons:

to remove tissue thatno longer has anadequate blood supply

to remove malignant

tumors because of severe

trauma to the body part

The goal of allamputations is twofold:

To remove diseased

tissue so that thewound will heal cleanly.

To construct a stumpthat will allow the

attachment of aprosthesis or artificialreplacement part.


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Although over 90% of

limb loss is "acquired",

up to 4% is congenital

(present at birth).

Of all the amputations

performed:

up to 90% are due to

vascular disease(circulation problems),

especially in people

with diabetes, but also

in non-diabetic


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While over 90% of

amputations due to

vascular disease involve

the lower limb, nearly70% of amputations

due to trauma involve

the upper limb.

The remaining ~10% are

needed, either after

limb trauma or as part

of the treatment forbenign or malignant

limb tumours.


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Complications of amputation

Joint deformity

Haematoma formation

Necrosis Wound opening from poor healing

Phantom limb syndrome


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A large proportion ofamputees (50-80%)experience thephenomenon ofphantom limbs.

They feel body partsthat are no longerthere.

These limbs can itch,ache, and feel as if theyare moving.

Some scientists believeit has to do with a kindof neural map that thebrain has of the body,which sends

information to the restof the brain about limbsregardless of theirexistence.


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Phantom sensations

and phantom pain may

also occur after the

removal of body partsother than the limbs.

e.g. after amputation of

the breast, extraction of

a tooth (phantom tooth

pain) or removal of aneye (phantom eye

syndrome).


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What is a prosthesis?

A prosthesis is an

artificial part of the

body that is custom

made and used in placeof the part that has

been lost.

An orthopedic

prosthesis is an internal

or external device that

replaces lost parts orfunction of the

neuroskeletomotor

system.


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Factors to consider when choosing prosthetic

components

Amputation level andresidual limb strength

Contour of the residuallimb

Health status

Physical status (ie, balance,strength) and fitness level

Effects of peripheral

vascular disease anddiabetic nephropathy,which may cause unstableresidual limb volume

other neurologic deficits(ie, stroke)

Sensorimotor deficitscaused by peripheral nervedysfunction


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Expected function and needs of the

prosthesis

Patient's vocation (for example, desk job vs

manual labor)

Patient's avocational interests (ie, hobbies)

The cosmetic importance of the prosthesis


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Acute postsurgical phase

The major issues in this phase are adequate

wound healing, pain management, the

administration of soft and rigid dressings for

limb shaping and exercises and to improvestrength and mobility.


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A skin desensitization program consists

of the following

Gentle tapping andmassage (with awashcloth) on the distalportion of the residual

limb Scar mobilization and

massage to preventexcessive scar formation

from causing the softtissues and skin to adhereto underlying bone

Edema control

The application ofpressure to the distalaspect of the residual

limb to prepare the limbfor weight acceptance


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A rigid, removable dressing may be used over

the residual limb during this phase

The rigid dressing servesthe following functions:

Aids in edema control andleads to rapid residual limb

shrinkage Promotes healing by

providing protection andpreventing edema

Desensitizes the limb

Prevents residual limbtrauma

Reduces wound pain


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Lower Limb Prosthesis

Loss of lower limb

causes :

Loss of Structural

support for the upperbody in standing

Along with complex

joint articulations and

muscular motor system

involved in walking

Apart from this ,

multimode sensory

feedback is lost ,

pressure sensors on thesole of the foot


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Length and force sensors in the muscles

And position sensors in the joints which closed

the control loop around the skeletomotor

system.

The body also has lost a significant percentage

of its weight and unbalanced.


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Lower Extremity Prosthesis

Components

The major components of a lower extremity

prosthesis are the socket (with or without a

socket liner)

a suspension system

interposed joint components (as needed)

a shank (pylon)

and a prosthetic foot.


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The socket

The socket serves as the

interface between the

residual limb and the

prosthesis.

It must not only protect

the residual limb but

must also appropriately

transmit the forcesassociated with

standing.


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The preparatory socket

can be created by using

a plaster mold of the

residual limb as atemplate

The preparatory

(temporary) socket will

likely need to be

adjusted several timesas the volume of the

residual limb stabilizes.


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Some prosthetic

manufacturing facilities

use computer-assisted

technology to map theresidual limb,

manufacturing a socket

directly from that data.


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patellar tendon-bearing (PTB) socket

The most common

socket used in a

transtibial amputation

is a patellar tendon-bearing (PTB) socket


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TSB

An alternative socket

design for transtibial

amputees is the TSB

socket that is used withan elastomeric liner

system.

When used with gel

liners, the TSB socket is

believed to distribute

pressures moreuniformly within the

socket


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The suspension mechanism

Need:

Every prosthesis

requires some type of

suspension system tokeep it from falling off

the residual limb.

Self-suspension of the

socket

Suction suspension

Suspension device orharness equipment


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The suspension mechanism

Suspension can be

achieved by a variety of

methods:

Suspension device orharness equipment :

includes belts, cuffs,

wedges, straps, and

sleeves.

Self-suspension of the

socket - This makes use

of the anatomic shape

of the residual limb(Syme or knee

disarticulation).


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Suction suspension :

Methods of creating

suction suspension

include the use of anappropriate suction

socket design, of a gel

suspension liner.

A bi ti f th t h i l


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A combination of these techniques also

can be used.

Standard suction is a

common suspension

choice for transfemoral

prostheses.

It employs a total-

contact, form-fitting,

rigid or semi rigid

socket with a 1-way airvalve in the distal end

that allows air to be

expelled after the

socket is donned.


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When air is driven outof the end of the

socket, a small negative

pressurestrong

enough to suspend thesocket on the residual

limbdevelops inside

the socket.

The socket's intimate fit

creates a seal between

the skin of the residual

limb and the socket.


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This form of suspension

allows excellent

proprioceptive feedback

and is lightweight.

One disadvantage of

the suction socket is its

inability to tolerate

much weight or volumefluctuation.


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A total elastic

suspension (TES) belt, a

single-axis knee with

extension assist,endoskeletal

components, and an

energy-storing foot

(anterior view).


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Lateral view with flexed

knee.


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Auxiliary suspension options for the patient with a

transfemoral amputation.


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Silesian belt The Silesian belt fastens

to the socket laterally,above the greatertrochanter, and wrapsaround the opposite

iliac crest. Because it does not

control rotation verywell, people using thistype of suspension belt

often have difficultywith internalrotation, especially ifthe residual limb isfleshy.


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TES(TOTAL ELASTIC SUSPENSION)

The TES belt is morecommonly used todaythan the Silesian beltand aids in rotational

control. It slips over the outside

of the prosthetic socketand surrounds the waistabove the iliac crest to

provide suspension.


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TES

The TES belt is made from the neoprene

material .


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SUCTION SUSPENSION SYSTEM

Patients with a

transfemoral or

transtibial amputation

may utilize the gelliner suction system,

which uses a gel

elastomeric liner.

The liner rolls onto the

residual limb and is

then inserted and

locked into the socket.


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This suspension system

can reduce shear

between the residual

limb and the socket,and minimizes pistoning

of the residual limb in

the socket.


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Heat buildup, skin problems, and decreased

proprioception can be drawbacks to this

suspension system


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Pelvic belt and band

A single-axis hip joint is

integrated into the

lateral socket wall and

pelvic band to controlrotation and is used for

weak hip adductors or

short residual limbs


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TRASFEMEORAL


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Auxiliary suspension options for patient with

a transtibial amputation.

Knee joint


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j

The prosthetic knee must fill the following 3functions:

Provide support during the stance phase ofambulation

Produce smooth control during the swing phase

Maintain unrestricted motion for sitting and

kneeling The prosthetic knee can have a single axis with

a simple hinge and a single pivot point, or it mayhave a polycentric axis with multiple centers ofrotation.


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TYPES OF KNEE

The manual-locking knee

The hydraulic knee

Polycentric knee

The hydraulic-based Otto Bock C-Leg

The weight-activated, or safety knee


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The manual-locking knee provides the most

stability, but the gait is awkward and energy

consuming.

Polycentric knees are heavy, costly, and

require high maintenance.


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The hydraulic knee

The hydraulic knee (pneumatic or oil) allowsfor cadence (tempo) variance.

This design uses a piston in a fluid-filledcylinder that accommodates the swing phaseof the patient's gait.

The knee is heavy, costly, and requires highmaintenance.

Th h d li b d Ott B k C


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The hydraulic-based Otto Bock C-

Leg The hydraulic-based

Otto Bock C-Leg (Otto

Bock Health Care,

Minneapolis, Minn)provides several

benefits over purely

mechanical knee

systems.

These microprocessor-

controlled knees

improve upon the

timing of the hydraulicand pneumatic knees



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Leg The patient can

ambulate at greater

speeds with optimal,

biomechanically correctsymmetry while

expending less energy.

Most importantly, the

user can safely walk

step over step up and

down stairs.



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Leg The built-in battery lasts

anywhere from 25-40hours, which meansthat it can support a full

day of activity.

The recharge can be

performed overnight

or while traveling in a

car (via a cigarettelighter adapter).

Th i h i d f k


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The weight-activated, or safety knee

The safety knee canaccommodate up to 20of kneeflexion, produces

friction, and preventsbuckling.

It allows ambulation on

uneven surfaces.

The safety knee is a

common initial

prosthetic knee for

geriatricpatients, persons with

extreme weakness, and

patients with poor hip

control


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The pylon and ankle

The pylon is a simpletube or shell thatattaches the socket tothe terminal device.

Pylons have progressedfrom simple, staticshells to dynamicdevices that allow axialrotation and that

absorb, store, andrelease energy

The pylon can be an

exoskeleton (soft foam

contoured to match the

other limb andcovered with a hard,

laminated shell) or an

endoskeleton (an

internal, metal framewith cosmetic soft

covering).


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The pylon and ankle

The ankle functionusually is incorporatedinto the terminaldevice.

A separate ankle jointcan be beneficial inheavy-duty industrialwork or in sports suchas mountain climbing,

swimming, and rowing.

However, theadditional weight of aseparate joint requiresmore energy

expenditure and greaterlimb strength to controlthe additional motion.

Th l d kl


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The pylon and ankle

P th ti f t


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Prosthetic feet

The 5 basic functions of the prosthetic footare as follows:

Provide a stable, weight-bearing surface

Absorb shock Replace lost muscle function

Replicate the anatomic joint

Restore cosmetic appearance


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Nonenergy-storing feet

Non

energy-storing

feet include the solid-

ankle/cushioned-heel

(SACH) foot and the

single-axis foot.

The single-axis foot

adds passive plantar

flexion and dorsiflexion,

which increase stability

during stance phase

and smooth gait


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Energy-storing feet

The energy-storing feet

are the multiaxis foot

and the dynamic-

response foot.

The multiaxis foot adds

inversion, eversion, and

rotation to plantar

flexion and dorsiflexion

It handles uneven

terrain well and is a

good choice for the

individual with a

minimal-to-moderate

activity level


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The dynamic-response foot is the top-of-the-

line foot and is commonly used by young

active individuals and athletic individuals with

amputations


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Lower limb prosthetics

SACH (single axis

composite heel) foot,

Seattle light foot

(energy storing footwith Delrin keel),

Carbon Copy II (energy

storing foot with carbon

keel).


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Lower limb prosthetics.

Seattle Light Foot

(energy storing foot

with Delrin keel).

The space between 1st

and 2nd toe, which

allows patient to wear

toe strap sandals

Documents

Unit 4 Prosthesis