University of Groningen Does Computer-Assisted Femur · PDF fileFemur First THR Improve Musculoskeletal Loading ... Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading

University of Groningen

Does Computer-Assisted Femur First THR Improve Musculoskeletal Loading ConditionsWeber Tim A Dendorfer Sebastian Grifka Joachim Verkerke Gijsbertus RenkawitzTobiasPublished inBiomed research international

DOI1011552015625317

IMPORTANT NOTE You are advised to consult the publishers version (publishers PDF) if you wish to cite fromit Please check the document version below

Document VersionPublishers PDF also known as Version of record

Publication date2015

Link to publication in University of GroningenUMCG research database

Citation for published version (APA)Weber T A Dendorfer S Grifka J Verkerke G J amp Renkawitz T (2015) Does Computer-AssistedFemur First THR Improve Musculoskeletal Loading Conditions Biomed research international 2015[625317] DOI 1011552015625317

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Download date 20-04-2018

Research ArticleDoes Computer-Assisted Femur First THR ImproveMusculoskeletal Loading Conditions

Tim A Weber12 Sebastian Dendorfer1 Joachim Grifka2

Gijsbertus J Verkerke34 and Tobias Renkawitz2

1Faculty of Mechanical Engineering Laboratory for Biomechanics Ostbayerische Technische Hochschule Regensburg93053 Regensburg Germany2Department of Orthopaedic Surgery Regensburg University Medical Center (UKR) 93077 Bad Abbach Germany3Department of Rehabilitation Medicine University Medical Center Groningen (UMCG) University of GroningenAntonius Deusinglaan 1 9713 AV Groningen Netherlands4Department of Biomechanical Engineering University of Twente Drienerlolaan 5 7522 NB Enschede Netherlands

Correspondence should be addressed to Tim A Weber timweberoth-regensburgde

Received 14 August 2014 Revised 15 November 2014 Accepted 26 November 2014

Academic Editor Michiaki Takagi

Copyright copy 2015 Tim A Weber et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We have developed a novel computer-assisted operation method for minimal-invasive total hip replacement (THR) following theconcept of ldquofemur firstcombined anteversionrdquo which incorporates various aspects of performing a functional optimization of theprosthetic stem and cup position (CAS FF)The purpose of this study is to assess whether the hip joint reaction forces and patientrsquosgait parameters are being improved by CAS FF in relation to conventional THR (CON) We enrolled 60 patients (28 CAS FF32CON) and invited them for gait analysis at three time points (preoperatively postop six months and postop 12 months) Dataretrieved from gait analysis was processed using patient-specific musculoskeletal models The target parameters were hip reactionforce magnitude (hrf) symmetries and orientation with respect to the cup Hrf in the CAS FF group were closer to a young healthynormal Phase-shift symmetry showed an increase in theCASFF groupHrf orientation in theCASFF groupwas closer to optimumthough no edge or rim-loading occurred in the CON group as well The CAS FF group showed an improved hrf orientation in anearly stage and a trend to an improved long-term outcome

1 Introduction

Total hip replacement (THR) is one of the most successfuloperations of the 20th century [1] Instability and early asepticloosening are the two most common early complicationsfollowing THR [2ndash5] Biomathematical calculations haveshown that prosthetic instability can be reduced by regardingstem and cup as coupled partners in a biomechanical system[6] In this context several authors have proposed startingwith the preparation of the femur and then transferring theorientation of the stem relative to the cup intraoperatively(ldquofemur firstrdquo ldquocombined anteversionrdquo) in order to mini-mize the risk of impingement and dislocation [7ndash10] Wehave developed a novel computer-assisted operationmethodfor THR following the concept of ldquofemur firstcombined

anteversionrdquo (CAS FF) which incorporates various aspectsof performing a functional optimization of the prostheticstem and cup position [11ndash13] Goal of this study was tocompare the hip reaction forces (hrf) and their orientationwhich are known to influence implant survivorship [14ndash16]betweenCASFF and conventional THR (CON)Onemethodto analyze hrf is to employ instrumented implants (II) [17 18]This method is regarded as the gold standard since it is theonly way to measure such forces in vivo however it bears thedisadvantage of being highly invasiveThis limits thismethodto only small sample sizes making statistical analysis andpredictions challenging Novel computational methods likemusculoskeletal modeling (MM) have the potential to accu-rately predict hrf while being noninvasive [19] Validationof such models has been achieved by comparing computed

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 625317 16 pageshttpdxdoiorg1011552015625317

2 BioMed Research International

entities to measured ones [20] After validation has beenachieved the models can be employed to investigate largercollectives [16] Often such studies focus on activities of dailyliving (ADL) such as walking [21] By combining experi-mental data as retrieved from motion capture gait analysismedical imaging and MM it is possible to build anatomicalcorrect models that represent the patient accurately [22]allowing the computation of muscle forces and hip reactionforces in a patient-specific manner [19] Such data can helpto further improve implant design and can be used formeasuring the outcome after THR [21] Analyzing stronglyvarying signals such as joint reaction forces is a challengingtask The question that often remains is if ldquocharacteristicsrdquo(such as local minima local maxima or signal slopes) showa distinct pattern or if they appear randomly [23] Dynamictime warping (dtw) has been established by Bender andBergmann in order to compute typical signals (TS) which areaiming to provide the best representation of time series [23]Parameters gathered during the dtw computations are also ameasure of signal similarity They represent different aspectsof such the phase shift and the magnitudes respectivelyHealthy and able-bodied persons walk in a symmetricalway [24] Following the concept of dynamic similarity thetime series of joint reaction force in healthy persons arealso symmetrical [25] Therefore an important outcome afterTHR is not only magnitude and orientation of hrf but alsosymmetry of hrf as a measure to what extent gait pattern ispathological

The purpose of the current study is to assess whetherthe artificial jointrsquos hip reaction forces and patientrsquos gaitparameters can be improved by CAS FF THR by means ofa combined workflow of experimental and computationalmethods relative to conventional THR The specific targetparameters were (i) Are the hip reaction forces closer to ahealthy young normal in the CAS FF group (ii) Are the hipreaction forces distributedmore symmetrically in the CAS FFgroup (iii) Is critical edge or rim-loading of the acetabularcup less likely to occur in the CAS FF group

2 Patients and Methods

21 Patients The study design procedures and informedconsent were approved by our local medical ethics commit-tee (number 10-121-0263) This single-center patient- andobserver-blinded randomized controlled trial was registeredat the German Clinical Trials Register under the Main ID(DRKS00000739)

Recruitment of participants inclusion and exclusion cri-teria and surgical procedures for this randomized controlledtrial have been published prior to the start of the study[11] Eligible participants between the ages of 50 and 75with an American Society of Anesthesiologists (ASA [26])score le3 were recruited from patients admitted for primaryuncemented unilateral (minimal or no osteoarthritis in theopposite hip) THA due to primary or secondary osteoarthri-tis Exclusion criteria were age lt50 and gt75 years ASA scoregt3 coxarthrosis secondary to hip dysplasia posttraumatichip deformities and prior hip surgery Informed consent was

Patient planned for THR

No prior hip traumaNo dysplasia

Primary THRn = 135

50 lt age lt 75

ASA le 3No

Exclu

ded

Yes

Assign randomly tointervention group

Eligible forgait analysis

(preop)

No

Yes

Excludedfrom

gait analysisstudy

Return for two follow-ups(6 months 12 months)4 lost to follow-up

60 complete datasetsCAS FF n = 28

CON n = 32

Figure 1 Flow chart of patient acquisition with inclusion criteriaaccording to Renkawitz et al [11]

acquired by one of four clinical investigators THA in allpatients was performed in the lateral decubitus position usinga minimally invasive single-incision anterolateral approach160 THAs were performed by four orthopaedic surgeonsfrom the Regensburg University Medical Center Each sur-geon had experience with more than 200 fluoroscopy and200 navigation-controlled THAs Press-fit acetabular com-ponents uncemented hydroxyapatite-coated stems (Pinnaclecup Corail stem DePuyWarsaw IN) standard (nondysplas-tic and nonoffset) polyethylene liners and metal heads with adiameter of 32mm were used in all patients

Patients were randomly allocated to receive either FemurFirst CAS THR or conventional THR see Figure 1 Patientcharacteristics according to allocation are presented in

BioMed Research International 3

Table 1 Patient characteristics by intervention group

Group Sample size(malefemale)

Age inyears mean

(SD)

Agerange

minmax

BMI ([kgm2])mean(SD)

BMIrange

minmax

ASA mode(frequency)

Blood loss [gdL]mean(SD)

OP-time[minutes] mean

(SD)

CAS FF 28(1018)

60(7) 5074 2673

(426) 19453522 2(21)

minus30(10)

71(15)

CON 32(1913)

62(8) 5074 2758

(308) 21643368 2(12)

minus33(12)

63(13)

Table 1 The random allocation sequence was computer-generated in a permuted block randomization designed bythe associate statistician using certificated randomizationsoftware (Rancode 36 Professional IDVGauting Germany)

22 Methods

221 Computer-Assisted Minimally Invasive Femur First THR(CAS FF) In the CAS Femur First group an imagelessnavigation system (BrainLAB Navigation System PrototypeHip 60 ldquoFemur Firstrdquo Feldkirchen Germany) with newlydeveloped prototype software was used [13]

222 Conventional Minimally Invasive THR (CON) Acetab-ular components were placed ldquofreehandrdquo without the useof any alignment guides The target acetabular componentposition for all patients was within the ldquosafe zonerdquo as definedby Lewinnek et al 18 (40∘plusmn 10∘ inclination and 15 plusmn 10

∘anteversion) [27]

223 Gait Analysis (GA) Sixty patients performed a 3Dmotion-capture (mocap) gait analysis of the lower extremity(SimiMotion Unterschleiszligheim Germany) at three timepoints (preoperative (t0) 6 months postoperative (t1) and12 months postoperative (t2)) Only patients that were ableto conduct a valid gait experiment (strike one force platewith one foot) were included in the GA-study A bonyand anatomical landmark based marker-set consisting of 27retroreflective markers was previously tested to record thepatient-specific gait pattern by means of six digital videocameras with a video sample rate of 70Hz [28] The patientswalked at self-selected speed on a 10m walkway while theground reaction forces were recorded simultaneously usingtwo force plates (Kistler Winterthur Schweiz sample rate1000Hz) In order to calculate joint position based onmarkerdata a static trial was conducted before the gait experimentstarted Prior to recording the patients were asked to walkon the walkway three to five times in order to acquaintthemselves with the laboratory situation One patient missedt1-gait analysis but returned for the t2-analysis

224 Musculoskeletal Modeling (MM) The measuredground reaction forces and trajectories of the mocapmarkersretrieved during gait analysis were used as the input forthe musculoskeletal model to compute the vectorial jointreaction forces during walking (Figure 2) Musculoskeletalanalysis was conducted using a commercial software

package (AnyBody Technology AS Aalborg Denmark) Ageneric and previously validated model [29 30] (AnyGaitAMMR16) was first scaled based on anthropometricmeasurements as an initial guess [31] This was followedby a nonlinear scaling algorithm based on the maker datagathered during the static trial further adapting the modelto the patient specific anatomy [22] The hip reactionforces were computed for one complete gait cycle with 150computation steps for every model (Figure 2) The muscleswere parameterized using the mechanical Hill-Type Musclemodel the tendons have been calibrated accordingly [32]The time-dependent muscle activity is determined by a cubicoptimization scheme and according to (1) Consider

119866 = sum

119894

(mf119894

119873119894

)

3

(1)

where 119866 is the objective function to estimate muscle activa-tion mf is themuscle force vector (mf

119894is the 119894th element) and

119873 is the normalizing factor (muscle strength) [33] 119866 is to beminimizedwhile the boundary conditions have to be satisfied(equilibrium fulfilled muscles can only pull) The 179 MM intotal were batch-processedwith the aid of parallel computingallowing eleven models to be computed at the same timeusing Matlab (Matlab Release 2013a The MathWorks IncNatick Massachusetts United States)

225 Method Verification Themeasurement chain was eval-uated with respect to different sources of variance (Table 2)Three healthy volunteer male subjects were invited (S1 19years 794 kg 173m S2 25 years 704 kg 169m S3 31 years734 kg 182m) to perform mocap gait analysis The scopeof the verification study was to evaluate the measurementchain and not to conduct a population study hence such anarrow patient collective was acquired Data was processedwith the same workflow as for the patient study To evaluatethe measurement chain the standard error of mean (SEM)of the respective target parameter (Table 2) was computedaccording to (2) with 119899 samples and a sample standarddeviation 120590 [34] Consider

SEM (119883) =120590

radic119899 (2)

226 Model Validation The hrf retrieved from our patientcohort were compared to the publicly available hip 98dataset (httpwwwortholoadcom) [17] Hrf retrieved fromhealthy individuals were checked against literature datawhich were obtained by using similar workflows [35]


Acquisition ofvolunteer patients- Anthropometrics

- Anatomy

Gait analysis- Motion capture

(marker trajectories)- Ground reaction force

Musculoskeletal model

ScalingInput

anthropometricsmocap data

Outputsegment lengths and masses

joint positions

Kinematic analysisInput

scaling gait analysisOutput

- gait pattern(joint angles)

Inverse dynamicsanalysis

Inputkinematic analysis

Outputjoint forces muscles forces

Input for

Input for

Figure 2 Study workflow combining experimental data with numerical simulations during gait

Table 2 Different sources of variance of the measurement chain and the studies in order to determine the standard error of mean

Research question Source of variance Study Target parameter

Is the result obtained dependenton the mocap analyst Mocap analyst

One healthy subject (S1) 1 gait analysis evaluated10 times by 3 different examiners A(experienced) B (experienced) and C (notexperienced)

Standard error of mean(SEM) of hrf-HRFSEM

How big is the influence ofmarker-placement on the resultsobtained

Mocapmdashmarkerplacement

One healthy subject (S1) 10 gait analysesapplication of marker set in alternating manner by2 analysts A (experienced) and B (experienced)

HRFSEM

Is the method robust enough toproduce repeatable results Measurement chain Three healthy subjects (S1 S2 and S3) 10 gait

analyses evaluated by 1 experienced analyst (A) HRFSEM

227 Dynamic Time Warping While arithmetic means canonly be formed at corresponding time-points 119891(119905

119894) dynamic

time warping is based on comparing every time-point1198911(1199051119896

) to every time-point 1198912(1199051119896

) This is done by com-puting the dtw matrix according to Bender and Bergmannand according to (3) Consider

119889 (1198911

(1198941) 1198912

(1198942)) = (120572

2

) (1198911

(1198941)

10038171003817100381710038171198911

1003817100381710038171003817

minus1198912

(1198942)

10038171003817100381710038171198912

1003817100381710038171003817

)

2

+ (1 minus 120572)2

(1198911015840

1

(1198941)

10038171003817100381710038171198911015840

1

1003817100381710038171003817

minus1198911015840

2

(1198942)

10038171003817100381710038171198911015840

2

1003817100381710038171003817

)

2

(3)

The two signals are then connected by minimizing thecumulated costs (4) along the ldquodtw pathrdquo ((5) Figure 3) [23]Consider

CC =

119873119896

sum

119894119896=1

119889 (1198911

(119908 (119894119896)) 1198912

(119908 (119894119896))) (4)

119908 (119894119896) = [(119894

1(119894119896)) (1198942

(119894119896)) 119894119896

= 1 2 119873119896] (5)

By minimizing the cumulated cost dtw takes the mostldquosimilarrdquo values into account and permits the computationof a ldquotypical signalrdquo (TS) rather than comparing fixed timepoints 119891

12(1199051119896

) While the difference between the meansignal and the TS is negligible when comparing ldquosimilar


d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2

ldquoSimilar signalsrdquo ldquoDifferent signalsrdquo

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

Computed matrix Computed matrix

Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()

Comparison of two signals (hrf) Comparison of two signals (hrf)

50

4

3

21

00 100

Stance ()

Mean signalTypical signal


Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)

Figure 3 Using dtw for computing the TS from ldquosimilarrdquo or ldquodifferentrdquo signals respectively (a) dtw matrix with optimized path (white)for similar (left) and varying (right) signals (b) Comparison of mean signal (full line) and TS (dashed line) from the similar signals (left)and varying signals (right) For similar signals there is practically no difference between the mean signal and the TS When comparingvarying signals the TS yield different characteristics (red circles) Circle 1 no sharp cutoff appears to be more harmonically circle 2 peak isunderestimated in mean signal and circle 3 peak values between mean signal and TS are practically the same

signalsrdquo (Figure 3) the strength of dtw is comparing varyingsignals as it is often the case when comparing joint reactionforces during walking (Figure 3) [23] By weighting thesignals accordingly it is also possible to compute the TS from

more than two signals as it was done for the comparison ofthe CAS FF and CON group

The path length is a measure of phase shift betweentwo signals (Figure 3) The cumulated cost along the path is


Forceinclination(wrt cup) Sa

gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf

Forceanteversion(wrt cup)

Figure 4 The definition of force orientation which is based upon the definition of acetabular orientation in the radiographic coordinatesystem according to Stansfield and Nicol [35]

a measure of magnitude similarity Asymmetries are beingcomputed between the operated and not-operated leg at t0t1 and t2 as well as between the operated leg and a normativedataset at t0 t1 and t2

228 Postprocessing Bagplots are used to visualize the dis-tribution of bivariate statistical data [36]The greater the areathat is being enclosed the wider the data is scattered andthe more asymmetrical the patients walk in terms of hrfPostprocessing was done using Matlab Hrf orientations arequantified in the radiographic coordinate system accordingto Murray (Figure 4) [37]

229 Statistics ANOVA tests for unequal sample size(119899CASFF = 28 119899CON = 32) including group interactionswere performed for all time-points (t0 t1 t2) divided byintervention groups on asymmetry parameters Significancelevel was set at 5 (120572 = 005) Differences betweenintervention groups in terms of age BMI blood-loss andoperation time were tested using the studentrsquos 119905-test (120572 =

005) or with a chi-squared test (120572 = 005) for categorical datasuch as the ASA score

3 Results

31 PatientmdashCharacteristics The groups showed no signifi-cant differences in terms of age BMI blood loss and diseasecategory (ASA-score) The operation time of the CAS FFgroup was significantly higher

32 Method Verification Figure 5 displays the verificationstudy results The mocap-analyst has a negligible influenceon the target parameters Marker Placement has the greatestinfluence on the target parameters The repeatability studyshows that results are indeed robust but care must be takenwhen conducting experiments A SEM of plusmn025 BW is an

estimate of how accurate the hrf during walking can be com-puted On the right hand side themaximumhrf of the normalsubjects as computed with the aforementioned workflow arecompared to literature (normal subjects computed hrf) [35](Figure 5) 978 of all models compute hrf that lie within the95 (plusmn196SD) confidence interval as published by Stansfieldand Nicol [35] We therefore considered the models valid forthis study

33 Model Validation Figure 6 displays the comparisonof computed hrf against measured hrf (hip98httpwwwortholoadcom) Measured hrf were obtainedfrom four subjects and between 11 and 31 months postop [17]therefore the measured hrf are shown against the computedhrf at t2 The results show good agreement especially at thefirst peak The second peak seems to be overestimated bythe computed hrf but one should note that the measuredhrf have been obtained by only four subjects makingvalid statistical analysis challenging The maximum hrf areup to twofold higher than measured ones however suchmagnitudes have been reported for healthy subjects [35]Themodels were considered valid for this study

34 Typical Signal (TS) of Hrf The TS as computed by dtwincluding the normalized walking speed according to Hofare shown in Figure 7 [38] The dimensionless walking speedincreases significantly over all follow-up points there are nosignificant differences between the two groups While thehrf at t0 are in the same magnitude and similar shape forboth groups the hrf are increasing over the follow-up periodThere are notable differences between the hrf at t1 for bothgroups the hrf in the CON group are greater when comparedto the CAS FF group (04 BW) bearing the SEM of plusmn025 BWin mind At t2 the hrf of the CAS FF group are furtherincreasing until becoming more similar to the healthy groupin terms of magnitude and shape At the second hrf peak of


025

02

015

01

005

SEM

in b

odyw

eigh

tSEM of reaction force

Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2

Stansfield and Nicol [35] (mean)

Validation of verification models

Hrf

inxlowast

body

wei

ght

Verification study experiments

Stansfield and Nicol [35] (plusmn196SD)

(b)

Figure 5 Results of the verification experiments (a) SEM of hrf as computed by different verification studies (b) Comparison of verificationmodel with literature data [34] including 95 confidence interval (plusmn196SD) of the literature data

Stance ()20 40 60 80 100

0

1

2

3

4

5

6

Computed hrf (median)Computed hrf (595 percentile)

Hip98 (median)Hip98 (595 percentile)

Computed hrf (at t2) versus measured hrf (hip98)

Hrf

inxlowast

body

wei

ght

Figure 6 Validation study of patient models The computed hrf are compared to the measured hrf (hip98-data) The hrf in multiples ofbodyweight (119910-axis) are displayed as a function of stance phase (0ndash100 during walking) The gray area indicates the 5 and 95 percentile for(all) hrf (operated side) at t2 the dark gray line represents the median thereof The blue lines represent either the hip98 median hrf (full line)or the 5 and 95 percentile (point-dashed line)

the CAS FF group there is practically no difference to dataretrieved from young healthy adults The hrf of the CONgroup do not further increase

35 Symmetries of Hrf Figure 8 displays the time seriessimilarities of joint reaction forces as computed by dtw by

means of bagplots [36] Figure 8(a) shows the comparison ofoperated leg versus not-operated leg Asymmetry measuresare the greatest in the CAS FF group at t0 thus those patientswere walking preoperative more asymmetrical than patientsin the CON group but this was not significant Duringthe follow-up period both groups improve significantly in


0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght

Typical hip reaction force

(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)

Walking speed at follow up points

015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d

Stansfield and Nicol [35]

(c)

Figure 7 The TS of the different THR-groups (a) The hrf of the CAS FF group at the different follow-up points can be seen (blue t0 greent1 red t2) The 119909-axis denotes the stance-phase in percent the 119910-axis shows the hrf in multiples of bodyweight The dashed line is the TSof the healthy group as gathered during the method verification experiments (b) Results for the CON group (blue t0 green t1 red t2) (c)Dimensionless walking speed computed according to Hof [38] at different follow-up points is displayed as well as literature data for THRpatients [35] (point-dashed dark red line)

phase shift similarity as well as in magnitude similaritythus patients are walking less asymmetrical at t2 Figure 8(b)displays the joint-reaction force time series of the operatedleg compared against the normative data Preoperative values

of the CAS FF group are not as scattered as for the CONgroup but the difference was not significant Phase shift andmagnitude symmetry increases in both groups significantlylarger improvements can be found for the CAS FF group In


Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1

t1 mediant2t2 median

t0

t0 mediant1


(b)

Figure 8 Bagplots of the deviation of joint reaction force time series as computed by dtw On the left row the CAS FF group is displayedwhereas on the right side the CON group is shown On all 119909-axes one can see the cumulated distance as computed by (4) (magnitudesimilarity) whereas on all 119910-axes the normalized path length as computed by (5) (phase shift similarity) is displayed (a) Comparison ofhrf time series for operated versus not operated side at the follow-up points (b) Comparison of hrf time series for operated versus normativedata at the follow-up points


Forc

e inc

linat

ion

wrt

cup

(deg

)

Force inclination at t1Force inclination at t1

P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)

Force anteversion at t1Force anteversion at t1

P = 0014

CAS FF CONCup anteversion

0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60

CAS FFCONOverall fit

CAS FF fitCON fit

(d)

Figure 9 The hrf orientation at peak loads of the CAS FF and the CON group was compared Left hrf orientation as a function of cuporientation including linear regression lines (black overall regression green regression line for CAS FF group magenta regression line forCON group) Blue cross CAS FF red plus CON Right boxplot of the hrf orientation at peak loads for the CAS FF and the CON group (a)Force inclination at t1 (b) force anteversion at t1 (c) force inclination at t2 and (d) force anteversion at t2

Table 3 Measure for the relationship between cup orientation andforce orientation wrt cup at 1199051 and 1199052

Overall CAS FF CON1199051

InclinationPearson correlation coefficient (119877) minus079 minus083 minus074Significance of correlation (119875) 90e minus 14 13e minus 07 13e minus 06

AnteversionPearson correlation coefficient (119877) minus049 minus041 minus048Significance of correlation (119875) 86e minus 05 0039 58e minus 03

1199052


AnteversionPearson correlation coefficient (119877) minus048 minus058 minus041Significance of correlation (119875) 00001 0002 0019

particular phase shift similarity at t2 increased in the CAS FFgroup more than in the CON group which is also supportedby the hrf-TS (Figure 7)

36 Orientation of Hrf at Peak Loads Figure 9 shows theforce inclination and force anteversion at t1 and t2 respec-tively The force inclination with respect to cup correlatessignificantly with the cup inclination in a linear fashion(119891(119909) = 119886 sdot 119909 + 119887) as does the anteversion at both follow-up points (Table 3) The coefficient of determination (1199032)

Table 4 Fit parameters for the linearmodel 119891(119909) = 119886sdot119909+119887 for forceorientation wrt cup orientation at 1199051 and 1199052 119909[cupdegree]

119886 (forcedegreecupdegree) 119887 (degree)1199051

InclinationOverall minus12 1093CAS FF minus14 1168CON minus10 1011

AnteversionOverall minus09 1092CAS FF minus06 984CON minus10 1124

1199052



is greatest at t1 for inclination of the CAS FF group (69variance explained by linear modelmdashTable 2) Roughly 25variance is explained by the linear model for the anteversionangleThe variance explained for inclination decreases to 55at t2 as does the correlation coefficient (minus083rarr minus074)At all follow-up points we performed a significance test


70

60

50

400 20 40 60

Combined anteversion

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60

Combined anteversion0 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)

Figure 10 The hrf orientation at peak loads of the CAS FF and the CON group versus the combined anteversion Left hrf inclination asa function of combined anteversion including linear regression lines (black overall regression green regression line for CAS FF groupmagenta regression line for CON group) Blue cross CAS FF red plus CON Right hrf inclination as a function of combined anteversionincluding linear regression lines (a) force orientation at t1 and (b) force orientation at t2

(studentrsquos 119905-test alpha = 5) between the CAS FF andthe CON group for the force angles We found significantdifferences for both angles at t1 which vanished at t2 Patientthat underwent CAS FF surgery showed force-angles closerto optimum (force angle = 90∘mdashforce attacks at center ofhemisphere) Table 4 lists the coefficients of the linear fitshowing good agreement for inclination angles Deriving alinear regression line for the anteversion is also possible butnot with the same quality as for inclination (Table 3)

37 Orientation of Hrf at Peak Loads with respect to CombinedAnteversion Figure 10 shows the force orientation (force

inclination and force anteversion) as a function of thecombined anteversion There is no relationship betweenthe force orientations of the CAS FF group (Table 5) Theforce anteversion of the CON group shows a significant butweak relationship to the combined anteversion (Table 5)The significant but weak relationship between the combinedanteversion and the force anteversion for both groups is aresult of the weak correlation for the CON group Even ifthere is a relationship between combined anteversion andforce orientation for the CON group only amaximum of 13of the variance of the data points can be explained indicatingonce more influences of other unknown factors


Table 5 Measure for the relationship between combined antever-sion and force orientation wrt cup at 1199051 and 1199052


Force inclinationPearson correlation coefficient (119877) 023 024 006Significance of correlation (119875) 008 023 074

Force anteversionPearson correlation coefficient (119877) minus037 minus001 minus036Significance of correlation (119875) 000 095 004

1199052



4 Discussion

The purpose of this study was to compare the hrf and theirorientation between CAS FF and conventional THR

The TS of the hrf shows improvement for the CAS FFgroup at the endpoint t2 when compared to normative dataStansfield and Nicol report similar walking speed for THRpatients postoperatively at comparable follow-up points [35]Both groups performed approximately the same at t0 evenif the asymmetries were greatest for the CAS FF group at t0The fact that the hrf are decreasing between t1 and t2 in theCON group can be attenuated to measurement noise Hrf asan integral measure for muscle forces are crucial for boneremodeling and bone in-growth [39 40] Therefore restoringthe hrf to young healthy adult ones as we observed it in ourstudy for the CAS FF group is the benchmark outcome forTHR Asymmetries of operated versus not-operated side inthe CAS FF group decrease more than in the CON groupbut the effect seems to be insignificant It is important to alsoinclude the asymmetries of operated side versus normativedata since walking can also be symmetrical if both sidesperform equally poor The CAS FF THR group walks closerto a healthy normal especially at t2 in terms of phase shiftmeaning local maxima and minima are more likely to occurat the same time of a gait cycle as for a young healthyadult This indicates a restored ability to walk [41] possiblyresulting in a long-term benefit for the patients operatedwith CAS FF with functional optimization Such long-termbenefit remains to be proven which can only be achievedwith additional follow-up points At t1 the TS hrf of the CONgroup are closer to a healthy normal but the force orientationfor the CAS FF group is closer to optimum than in the CONgroup Not only hrf magnitude is crucial for the implantsurvivorship but also the orientation of the hrf [21] Hrf thatare closer to the edge of acetabular cup may result in edgeor rim-loading therefore increasing wear and compromisingimplant-survivorship [16] While the hrf anteversion andinclination in theCAS FF group appears to bemore favorable

the hrf orientation in the CONgroup is still noncritical whentaking into account that the inlay of the cup gets thinner onthe edge (pinnacleduraloc) due to manufacturing reasons[42] Measurements taken from Effenberger and Hrsg [43]show that there are indeed cups where force orientation suchas presented would result in rim-loading but especially wearcomputations are necessary to identify critical regions in thecup [44] to back up this hypothesisThe significant differencein hrf orientation with respect to cup between the CAS FFand CON groups vanishes at t2 indicating that over thefollow-up period the orientation as found in the CON groupadjusts to similar hrf orientations found in the CAS FF groupbecoming closer to optimum Our data suggests that theCAS FF procedure with functional optimization is especiallybeneficial at an early stage and has the potential to decreasethe propensity for rim-loading and therefore dislocation andimpingement within the first weeks after surgery We alsoinvestigated a possible linear relationship between cup angleand force orientation and found a significant correlationbetween the force inclination and cup inclination at t1 witha high coefficient of correlation (minus075)The other angles alsorevealed a nonzero relationship but the explained variancedecreases over follow-up period (Table 3) This indicates thatwith a greater cup inclination andor anteversion the anglebetween the resultant hip reaction force and the rim of thecup decreases Therefore the resultant hip reaction force getscloser to the rim of the cupThis relationship becomes indeedvaluable when thinking of applying these results to eitherpreoperational planning or real-time biomechanical feedbackduring surgery which only CAS systems could provide Thefact that the correlation coefficient decreases over the follow-up period shows that other influences may play an importantrole (implant shaft gait pattern) and that the relationship ismulti-factorialTheweak or nonexistent relationship betweenthe combined anteversion and force orientation supportsthis assumption The force orientation cannot only be solelyexplained with implant orientation This shows that for thedefinition of an implant safe-zone based on biomechanicalevaluations the patient-specific anatomy and integral motionpattern is of vital importance Based on such biomechanicalevaluations a patient-specific optimal implant safe-zone mayexist which remains to be proven

To the authors knowledge this is the first study thatincludes musculoskeletal models of gait in a prospectiverandomized controlled trial studying the computer-assistedfemur first technique in relation to conventional THR Otherstudies have been conducted to either study early outcome ofstandard CAS after THR by means of gait analysis [45] or tostudy the influence of surgical approach on gait parameters[46 47] The results of the gait analysis of these studies aremostly concise with our findings There are no differencesin temporospatial parameters such as walking speed orkinematic parameters One study also compared muscleactivation profiles of patients that underwent either MIS orconventional THR during walking which also did not revealany significant differences [46]MMhave also been employedto study the outcome of THR but only on an individual basisor with a small not randomized study population [16 21 48]They all used the same validated musculoskeletal model and


investigated similar parameters (edge-loading total hrf) Noevidence of occurring edge-loading in the studied populationwas found which agrees with our findings

41 Strengths We investigated a rather large patient cohortspeaking for this kind of study (combining gait analysis withMM) which was also patient and observer blinded To ourknowledge this is the first study that has used this specificnovel navigation algorithm in clinical practice To the best ofour knowledge this is also the first study ever with a patient-and observer-blinded prospective randomized controlledstudy design on navigation in THR that has been published inthe literature The validated MM were highly patient-specificand we are confident that the models reflect the in vivo loadsas accurate as possible using such a workflow Comparingstrongly varying signals by means of dtw has the advantageto not only focus on particular time points of signal timeseries It rather compares all time-points to all time-pointsThis makes subjective and observer based decisions obsoleteTo our knowledge and based on Bender and Bergmann [23]theTS as computed by dtw is the best representation of typicalpatterns as they occur in time series

42 Limitations Since the MM are purely mechanical mod-els psychological effect are cancelled out By also analyzingclinical outcome scores (such as the Harris Hip Score (HHS)or the hip osteoarthritis outcome score (HOOS)) we triedto counter such effects however the scores revealed nodifferences at t1 or t2 respectively The movement of theupper body has not been quantified using motion captureThe measurement volume of the mocap is too small toeffectively capture themovement of the body segments abovethe pelvisThe integral movement of the upper body has beenapproximated by mechanically balance the center of massabove the pelvisThis does not however reflect themovementit is rather an approximation We also did not includethe patientsrsquo physical activity (PA) particularly Evaluatingthe individual PA is very challenging since the methodsto evaluate PA are biased or can be deceived easily [49]Gait performance in the laboratory may reflect the levelof PA in and that is how we included this effect Patientswith higher levels of PA may recover faster than othersTherefore the results may be biased due to PA level ofevery particular patient This is an effect that can only becountered by evaluating large patient cohorts Even thoughthe biomechanics are crucial for the functioning of one of thelargest and weight-bearing joints in the human body it is notcompletely sure that improved biomechanics also leads to animproved clinical outcome Current research however showsthat improved biomechanics leads to an improved outcomefor the patient [50 51] Also biomechanical parameters havebeen found to be clinically relevant [52]

43 Clinical Relevance We suggest practical application forour work such as operational planning based on biomechan-ical parameters (preop gait pattern orientation of cup versushrf orientation) by deriving simple laws and algorithmsfrom the data The results can also be used for real-time

biomechanical feedback during CAS which is a scope forfurther research A new safe-zone for implant componentposition and orientation is also thinkable which relies onan accurate statistical model This would draw the focus ofimplant positioning rather on analytical laws then experi-ence Future research will also include detailed finite elementmodels based on patient specific medical imaging data andpatient-specificmuscle forces and boundary conditions Suchmodeling will give more insight into implant bone contactstresses and wear in the hip joint both are important for theprediction of implant survivorship

5 Conclusion

The computer-assisted THRmethod following the concept offemur firstcombined anteversion does lead to an improvedoutcome in contrast to conventional THR six month aftersurgery In Particular force orientation is close to optimumfor the novel CAS Femur First technique at an early stageA trend for decreased asymmetries of the gait pattern ofthe CAS FF group compared to the CON group indicates arestored walking ability and therefore a possible long-termbenefit for the patients however this hypothesis can only beproven by repeating the experiments at additional follow-uppoints

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of the paper

Acknowledgments

Thiswork received funding fromDePuy International LeedsUK as well as from ldquoTechnologie und WissenstransferOstbayernrdquoThe authors are also grateful for support fromMrSuszlig Regensburg Center of Biomedical Engineering for helpwith the dtw algorithm Mr Zeman UniversitatsklinikumRegensburg Zentrum fur klinische Studien for support inthe statistical analysis and Mr Waller Universitat Regens-burg British Studies for the revision of this paper

References

[1] I D Learmonth C Young and C Rorabeck ldquoThe operationof the century total hip replacementrdquo The Lancet vol 370 no9597 pp 1508ndash1519 2007

[2] K J Bozic S M Kurtz E Lau K Ong D T P Vail and D JBerry ldquoThe epidemiology of revision total hip arthroplasty inthe united statesrdquo The Journal of Bone amp Joint Surgery vol 91no 1 pp 128ndash133 2009

[3] S Graves D Davidson and A Tomkins ldquoAustralianOrthopaedic Association National Joint Replacement RegistryAnnual Report 2013rdquo Adelaide Australia 2009

[4] D Emsley J Martin C Newell and M PickfordNational JointRegistry for England and Wales 5th Annual Report 2008 2012

[5] A Malik A Maheshwari and L D Dorr ldquoImpingement withtotal hip replacementrdquo Journal of Bone and Joint Surgery A vol89 no 8 pp 1832ndash1842 2007


[6] T Renkawitz M Tingart J Grifka E Sendtner and T KalteisldquoComputer-assisted total hip arthroplasty coding the next gen-eration of navigation systems for orthopedic surgeryrdquo ExpertReview of Medical Devices vol 6 no 5 pp 507ndash514 2009

[7] C S Ranawat and M J Maynard ldquoModern technique ofcemented total hip arthroplastyrdquo Techniques in Orthopaedicsvol 6 no 3 pp 17ndash25 1991

[8] K H Widmer and B Zurfluh ldquoCompliant positioning oftotal hip components for optimal range of motionrdquo Journal ofOrthopaedic Research vol 22 no 4 pp 815ndash821 2004

[9] L D Dorr A Malik M Dastane and Z Wan ldquoCom-bined anteversion technique for total hip arthroplastyrdquo ClinicalOrthopaedics and Related Research vol 467 no 1 pp 119ndash1272009

[10] K-H Widmer ldquoContainment versus impingement findinga compromise for cup placement in total hip arthroplastyrdquoInternational Orthopaedics vol 31 supplement 1 pp S29ndashS332007

[11] T Renkawitz M Haimerl L Dohmen et al ldquoMinimallyinvasive computer-navigated total hip arthroplasty followingthe concept of femur first and combined anteversion designof a blinded randomized controlled trialrdquo BMCMusculoskeletalDisorders vol 12 article 192 2011

[12] T Renkawitz M Haimerl L Dohmen et al ldquoThe associationbetween Femoral Tilt and impingement-free range-of-motionin total hip arthroplastyrdquo BMC Musculoskeletal Disorders vol13 article 65 2012

[13] T Renkawitz M Haimerl L Dohmen et al ldquoDevelopment andevaluation of an image-free computer-assisted impingementdetection technique for total hip arthroplastyrdquoProceedings of theInstitution of Mechanical Engineers Part H vol 226 no 12 pp911ndash918 2012

[14] E Ingham and J Fisher ldquoBiological reactions to wear debrisin total joint replacementrdquo Proceedings of the Institution ofMechanical Engineers PartH Journal of Engineering inMedicinevol 214 no 1 pp 21ndash37 2000

[15] T P Culleton P J Prendergast andD Taylor ldquoFatigue failure inthe cement mantle of an artificial hip jointrdquo Clinical Materialsvol 12 no 2 pp 95ndash102 1993

[16] S J Mellon G Grammatopoulos M S Andersen et alldquoIndividual motion patterns during gait and sit-to-stand con-tribute to edge-loading risk in metal-on-metal hip resurfacingrdquoProceedings of the Institution of Mechanical Engineers Part HJournal of Engineering in Medicine vol 227 no 7 pp 799ndash8102013

[17] G Bergmann G Deuretzbacher M Heller et al ldquoHip contactforces and gait patterns from routine activitiesrdquo Journal ofBiomechanics vol 34 no 7 pp 859ndash871 2001

[18] N W Rydell ldquoForces acting on the femoral head-prosthesisA study on strain gauge supplied prostheses in living personsrdquoActa Orthopaedica Scandinavica vol 37 supplement 88 pp 1ndash132 1966

[19] S Dendorfer T Weber and O Kennedy ldquoMusculoskeletalmodeling for hip replacement outcome analyses and otherapplicationsrdquo Journal of the American Academy of OrthopaedicSurgeons vol 22 no 4 pp 268ndash269 2014

[20] M E Lund M de Zee M S Andersen and J Rasmussen ldquoOnvalidation of multibody musculoskeletal modelsrdquo Proceedingsof the Institution of Mechanical Engineers Part H Journal ofEngineering in Medicine vol 226 no 2 pp 82ndash94 2012

[21] T Weber S Dendorfer S Dullien J Grifka G J Verkerkeand T Renkawitz ldquoMeasuring functional outcome after total

hip replacement with subject-specific hip joint loadingrdquo Pro-ceedings of the Institution of Mechanical Engineers H Journal ofEngineering in Medicine vol 226 no 12 pp 939ndash946 2012

[22] M S Andersen S J Mellon and M Lund ldquoThe effect ofincluding accurate pelvis bony landmarks in a nonlinearlyscaled musculoskeletal lower extremity modelrdquo in Proceedingsof the 12th International Symposium on 3D Analysis of HumanMovement pp 2ndash4 2012

[23] A Bender andG Bergmann ldquoDetermination of typical patternsfrom strongly varying signalsrdquo Computer Methods in Biome-chanics and Biomedical Engineering vol 15 no 7 pp 761ndash7692012

[24] R A Zifchock I Davis and J Hamill ldquoKinetic asymmetryin female runners with and without retrospective tibial stressfracturesrdquo Journal of Biomechanics vol 39 no 15 pp 2792ndash27972006

[25] R M Alexander and A S Jayes ldquoA dynamic similarity hypoth-esis for the gaits of quadrupedal mammalsrdquo Journal of Zoologyvol 201 no 1 pp 135ndash152 2009

[26] M Daabiss ldquoAmerican society of anaesthesiologists physicalstatus classificationrdquo Indian Journal of Anaesthesia vol 55 no2 pp 111ndash115 2011

[27] G E Lewinnek J L Lewis R Tarr C L Compere andJ R Zimmerman ldquoDislocations after total hip-replacementarthroplastiesrdquoThe Journal of Bone amp Joint Surgery vol 60 no2 pp 217ndash220 1978

[28] T Weber S Dullien J Grifka T Renkawitz and S DendorferldquoValidation of a motion capture laboratory and a new markerplacement protocol for clinical applicationsrdquo Gait Posture vol38 pp S113ndashS114 2013

[29] A Petrella J Rasmussen A A Al-Munajjed M DamsgaardM Lund and A Kiis ldquoHow good is good enough Lessons inmusculoskeletal model validation wit the AnyBody ModelingSystemrdquo in Proceedings of the ASMEFDA 1st Annual FrontiersinMedical Devices Applications of ComputerModeling and Sim-ulation (FMD 13) pp 11ndash12 Washington DC USA September2013

[30] C Manders A New and J Rasmussen ldquoValidation of muscu-loskeletal gait simulation for use in investigation of total hipreplacementrdquo Journal of Biomechanics vol 41 supplement 1 pS488 2008

[31] C L C Vaughan B Davis and J OrsquoConnor Dynamics ofHuman Gait Human Kinetics 1992

[32] F E Zajac ldquoMuscle and tendon properties models scalingand application to biomechanics and motor controlrdquo CriticalReviews in Biomedical Engineering vol 17 no 4 pp 359ndash4111989

[33] M Damsgaard J Rasmussen S T Christensen E Surma andM de Zee ldquoAnalysis ofmusculoskeletal systems in theAnyBodyModeling Systemrdquo Simulation Modelling Practice and Theoryvol 14 no 8 pp 1100ndash1111 2006

[34] J M Bland and D G Altman ldquoMeasurement error andcorrelation coefficientsrdquo British Medical Journal vol 313 no7048 pp 41ndash42 1996

[35] B W Stansfield and A C Nicol ldquoHip joint contact forces innormal subjects and subjects with total hip prostheses walkingand stair and ramp negotiationrdquo Clinical Biomechanics vol 17no 2 pp 130ndash139 2002

[36] P Rousseeuw ldquoThe bagplot a bivariate boxplotrdquoThe AmericanStatistician pp 37ndash41 1999


[37] D W Murray ldquoThe definition and measurement of acetabularorientationrdquo The Journal of Bone amp Joint Surgery B vol 75 no2 pp 228ndash232 1993

[38] A L Hof ldquoScaling gait data to body sizerdquo Gait and Posture vol4 no 3 pp 222ndash223 1996

[39] C Bitsakos J Kerner I Fisher and A A Amis ldquoThe effect ofmuscle loading on the simulation of bone remodelling in theproximal femurrdquo Journal of Biomechanics vol 38 no 1 pp 133ndash139 2005

[40] R Huiskes R Rulmerman G H van Lenthe and J D JanssenldquoEffects of mechanical forces onmaintenance and adaptation ofform in trabecular bonerdquo Nature vol 405 no 6787 pp 704ndash706 2000

[41] H Sadeghi P Allard F Prince and H Labelle ldquoSymmetry andlimb dominance in able-bodied gait a reviewrdquo Gait amp Posturevol 12 no 1 pp 34ndash45 2000

[42] J Schryver J Shea and D M Ryan Acetabular Cup BodyProsthesis 1994

[43] Z Effenberger and R Hrsg ldquoPressfitpfannen [GebundeneAusgabe]rdquo MCUmdashMedical Corporate University 2004

[44] T A Maxian T D Brown D R Pedersen and J JCallaghan ldquoThe Frank Stinchfield Award 3-Dimensional slid-ingcontact computational simulation of total hipwearrdquoClinicalOrthopaedics and Related Research no 333 pp 41ndash50 1996

[45] I H F Reininga M Stevens R Wagenmakers et al ldquoCom-parison of gait in patients following a computer-navigatedminimally invasive anterior approach and a conventional pos-terolateral approach for total hip arthroplasty a randomizedcontrolled trialrdquo Journal of Orthopaedic Research vol 31 no 2pp 288ndash294 2013

[46] M Pospischill A Kranzl B Attwenger and K Knahr ldquoMini-mally invasive compared with traditional transgluteal approachfor total hip arthroplasty a comparative gait analysisrdquo Journalof Bone and Joint SurgerymdashSeries A vol 92 no 2 pp 328ndash3372010

[47] D Bennett L Ogonda D Elliott L Humphreys and D EBeverland ldquoComparison of gait kinematics in patients receivingminimally invasive and traditional hip replacement surgery aprospective blinded studyrdquo Gait amp Posture vol 23 no 3 pp374ndash382 2006

[48] S J Mellon M S Andersen G Grammatopoulos and HS Gill ldquoMal-positioning alone does not necessarily lead toincreased wear in metal-on-metal hip resurfacingrdquo in Proceed-ings of the ORS Annual Meeting vol 79 of Abstract p 2011 SanFrancisco Calif USA

[49] M Morlock E Schneider A Bluhm et al ldquoDuration andfrequency of every day activities in total hip patientsrdquo Journalof Biomechanics vol 34 no 7 pp 873ndash881 2001

[50] M Sliwinski and S Sisto ldquoGait quality of life and theirassociation following total hip arthroplastyrdquo Journal of GeriatricPhysical Therapy vol 29 no 1 pp 10ndash17 2006

[51] P J James A C Nicol and D L Hamblen ldquoA comparison ofgait symmetry and hipmovements in the assessment of patientswith monarticular hip arthritisrdquo Clinical Biomechanics vol 9no 3 pp 162ndash166 1994

[52] C L Christiansen and J E Stevens-Lapsley ldquoWeight-bearingasymmetry in relation to measures of impairment and func-tional mobility for people with knee osteoarthritisrdquo Archives ofPhysical Medicine and Rehabilitation vol 91 no 10 pp 1524ndash1528 2010

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

ObesityJournal of



Computational and Mathematical Methods in Medicine

OphthalmologyJournal of


Diabetes ResearchJournal of



Research and TreatmentAIDS


Gastroenterology Research and Practice


Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom

Research ArticleDoes Computer-Assisted Femur First THR ImproveMusculoskeletal Loading Conditions

Tim A Weber12 Sebastian Dendorfer1 Joachim Grifka2

Gijsbertus J Verkerke34 and Tobias Renkawitz2

1Faculty of Mechanical Engineering Laboratory for Biomechanics Ostbayerische Technische Hochschule Regensburg93053 Regensburg Germany2Department of Orthopaedic Surgery Regensburg University Medical Center (UKR) 93077 Bad Abbach Germany3Department of Rehabilitation Medicine University Medical Center Groningen (UMCG) University of GroningenAntonius Deusinglaan 1 9713 AV Groningen Netherlands4Department of Biomechanical Engineering University of Twente Drienerlolaan 5 7522 NB Enschede Netherlands

Correspondence should be addressed to Tim A Weber timweberoth-regensburgde

Received 14 August 2014 Revised 15 November 2014 Accepted 26 November 2014

Academic Editor Michiaki Takagi

Copyright copy 2015 Tim A Weber et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

We have developed a novel computer-assisted operation method for minimal-invasive total hip replacement (THR) following theconcept of ldquofemur firstcombined anteversionrdquo which incorporates various aspects of performing a functional optimization of theprosthetic stem and cup position (CAS FF)The purpose of this study is to assess whether the hip joint reaction forces and patientrsquosgait parameters are being improved by CAS FF in relation to conventional THR (CON) We enrolled 60 patients (28 CAS FF32CON) and invited them for gait analysis at three time points (preoperatively postop six months and postop 12 months) Dataretrieved from gait analysis was processed using patient-specific musculoskeletal models The target parameters were hip reactionforce magnitude (hrf) symmetries and orientation with respect to the cup Hrf in the CAS FF group were closer to a young healthynormal Phase-shift symmetry showed an increase in theCASFF groupHrf orientation in theCASFF groupwas closer to optimumthough no edge or rim-loading occurred in the CON group as well The CAS FF group showed an improved hrf orientation in anearly stage and a trend to an improved long-term outcome

1 Introduction

Total hip replacement (THR) is one of the most successfuloperations of the 20th century [1] Instability and early asepticloosening are the two most common early complicationsfollowing THR [2ndash5] Biomathematical calculations haveshown that prosthetic instability can be reduced by regardingstem and cup as coupled partners in a biomechanical system[6] In this context several authors have proposed startingwith the preparation of the femur and then transferring theorientation of the stem relative to the cup intraoperatively(ldquofemur firstrdquo ldquocombined anteversionrdquo) in order to mini-mize the risk of impingement and dislocation [7ndash10] Wehave developed a novel computer-assisted operationmethodfor THR following the concept of ldquofemur firstcombined

anteversionrdquo (CAS FF) which incorporates various aspectsof performing a functional optimization of the prostheticstem and cup position [11ndash13] Goal of this study was tocompare the hip reaction forces (hrf) and their orientationwhich are known to influence implant survivorship [14ndash16]betweenCASFF and conventional THR (CON)Onemethodto analyze hrf is to employ instrumented implants (II) [17 18]This method is regarded as the gold standard since it is theonly way to measure such forces in vivo however it bears thedisadvantage of being highly invasiveThis limits thismethodto only small sample sizes making statistical analysis andpredictions challenging Novel computational methods likemusculoskeletal modeling (MM) have the potential to accu-rately predict hrf while being noninvasive [19] Validationof such models has been achieved by comparing computed

Hindawi Publishing CorporationBioMed Research InternationalVolume 2015 Article ID 625317 16 pageshttpdxdoiorg1011552015625317









Primary THRn = 135

50 lt age lt 75

ASA le 3No

Exclu

ded

Yes



(preop)

No

Yes

Excludedfrom

gait analysisstudy



CON n = 32







Age inyears mean

(SD)

Agerange

minmax


BMIrange

minmax

ASA mode(frequency)



(SD)

CAS FF 28(1018)

60(7) 5074 2673

(426) 19453522 2(21)

minus30(10)

71(15)

CON 32(1913)

62(8) 5074 2758

(308) 21643368 2(12)

minus33(12)

63(13)


22 Methods







119866 = sum

119894

(mf119894

119873119894

)

3

(1)





SEM (119883) =120590

radic119899 (2)




- Anatomy




ScalingInput



joint positions







Input for

Input for










HRFSEM




119894) dynamic




119889 (1198911

(1198941) 1198912

(1198942)) = (120572

2

) (1198911

(1198941)

10038171003817100381710038171198911

1003817100381710038171003817

minus1198912

(1198942)

10038171003817100381710038171198912

1003817100381710038171003817

)

2

+ (1 minus 120572)2

(1198911015840

1

(1198941)

10038171003817100381710038171198911015840

1

1003817100381710038171003817

minus1198911015840

2

(1198942)

10038171003817100381710038171198911015840

2

1003817100381710038171003817

)

2

(3)


CC =

119873119896

sum

119894119896=1

119889 (1198911

(119908 (119894119896)) 1198912

(119908 (119894119896))) (4)

119908 (119894119896) = [(119894

1(119894119896)) (1198942

(119894119896)) 119894119896

= 1 2 119873119896] (5)


12(1199051119896



d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2


500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue


Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()


50

4

3

21

00 100

Stance ()



Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)







gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
























Primary THRn = 135

50 lt age lt 75

ASA le 3No

Exclu

ded

Yes



(preop)

No

Yes

Excludedfrom

gait analysisstudy



CON n = 32







Age inyears mean

(SD)

Agerange

minmax


BMIrange

minmax

ASA mode(frequency)



(SD)

CAS FF 28(1018)

60(7) 5074 2673

(426) 19453522 2(21)

minus30(10)

71(15)

CON 32(1913)

62(8) 5074 2758

(308) 21643368 2(12)

minus33(12)

63(13)


22 Methods







119866 = sum

119894

(mf119894

119873119894

)

3

(1)





SEM (119883) =120590

radic119899 (2)




- Anatomy




ScalingInput



joint positions







Input for

Input for










HRFSEM




119894) dynamic




119889 (1198911

(1198941) 1198912

(1198942)) = (120572

2

) (1198911

(1198941)

10038171003817100381710038171198911

1003817100381710038171003817

minus1198912

(1198942)

10038171003817100381710038171198912

1003817100381710038171003817

)

2

+ (1 minus 120572)2

(1198911015840

1

(1198941)

10038171003817100381710038171198911015840

1

1003817100381710038171003817

minus1198911015840

2

(1198942)

10038171003817100381710038171198911015840

2

1003817100381710038171003817

)

2

(3)


CC =

119873119896

sum

119894119896=1

119889 (1198911

(119908 (119894119896)) 1198912

(119908 (119894119896))) (4)

119908 (119894119896) = [(119894

1(119894119896)) (1198942

(119894119896)) 119894119896

= 1 2 119873119896] (5)


12(1199051119896



d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2


500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue


Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()


50

4

3

21

00 100

Stance ()



Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)







gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of



















Age inyears mean

(SD)

Agerange

minmax


BMIrange

minmax

ASA mode(frequency)



(SD)

CAS FF 28(1018)

60(7) 5074 2673

(426) 19453522 2(21)

minus30(10)

71(15)

CON 32(1913)

62(8) 5074 2758

(308) 21643368 2(12)

minus33(12)

63(13)


22 Methods







119866 = sum

119894

(mf119894

119873119894

)

3

(1)





SEM (119883) =120590

radic119899 (2)




- Anatomy




ScalingInput



joint positions







Input for

Input for










HRFSEM




119894) dynamic




119889 (1198911

(1198941) 1198912

(1198942)) = (120572

2

) (1198911

(1198941)

10038171003817100381710038171198911

1003817100381710038171003817

minus1198912

(1198942)

10038171003817100381710038171198912

1003817100381710038171003817

)

2

+ (1 minus 120572)2

(1198911015840

1

(1198941)

10038171003817100381710038171198911015840

1

1003817100381710038171003817

minus1198911015840

2

(1198942)

10038171003817100381710038171198911015840

2

1003817100381710038171003817

)

2

(3)


CC =

119873119896

sum

119894119896=1

119889 (1198911

(119908 (119894119896)) 1198912

(119908 (119894119896))) (4)

119908 (119894119896) = [(119894

1(119894119896)) (1198942

(119894119896)) 119894119896

= 1 2 119873119896] (5)


12(1199051119896



d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2


500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue


Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()


50

4

3

21

00 100

Stance ()



Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)







gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















- Anatomy




ScalingInput



joint positions







Input for

Input for










HRFSEM




119894) dynamic




119889 (1198911

(1198941) 1198912

(1198942)) = (120572

2

) (1198911

(1198941)

10038171003817100381710038171198911

1003817100381710038171003817

minus1198912

(1198942)

10038171003817100381710038171198912

1003817100381710038171003817

)

2

+ (1 minus 120572)2

(1198911015840

1

(1198941)

10038171003817100381710038171198911015840

1

1003817100381710038171003817

minus1198911015840

2

(1198942)

10038171003817100381710038171198911015840

2

1003817100381710038171003817

)

2

(3)


CC =

119873119896

sum

119894119896=1

119889 (1198911

(119908 (119894119896)) 1198912

(119908 (119894119896))) (4)

119908 (119894119896) = [(119894

1(119894119896)) (1198942

(119894119896)) 119894119896

= 1 2 119873119896] (5)


12(1199051119896



d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2


500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue


Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()


50

4

3

21

00 100

Stance ()



Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)







gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















d(f1(i1) f2(i2)) = (1205722)(f1(i1)

f1minusf2(i2)

f2+ (1 minus 120572)2(

f9984001(i1)

f9984001minusf9984002(i2)

f9984002(2

(2


500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue

500400

300200

100

500400

300200

100 Target signal

Reference signal

40

30

20

10

0

dtw

val

ue


Find

opt

imal

pat

h (w

hite

) thr

ough

dtw

mat

rix

(a)

50

4

3

2

1

3

2

1

00 100

Stance ()


50

4

3

21

00 100

Stance ()



Hrf

inxlowast

body

wei

ght

Hrf

inxlowast

body

wei

ght

Com

paris

on b

etw

een

mea

n an

d ty

pica

l sig

nal

(b)







gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















gitta

l pla

ne

Hrf

Transverse planeCup

inclination

Sagittal Coronal

Cup

Transversal

anteversion

Sagittal plane

Cor

onal

pla

ne

Hrf







3 Results







025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















025

02

015

01

005

SEM

in b

odyw

eigh


Ana

lyst

A

Ana

lyst

B

Ana

lyst

C

Mar

ker

plac

emen

t A

Mar

ker

plac

emen

t B

Subj

ect1

Subj

ect2

Subj

ect3

RightLeft

(a)

7

6

5

4

3

2



Hrf

inxlowast

body

wei

ght



(b)


Stance ()20 40 60 80 100

0

1

2

3

4

5

6




Hrf

inxlowast

body

wei

ght






0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















0 50 100Stance ()

t0

t1

t2

Norm

1

15

2

25

3

35

4

45H

rf in

bod

ywei

ght


(a)

t0

t1

t2

Norm

0 50 1001

15

2

25

3

35

4

45

Stance ()H

rf in

bod

ywei

ght


(b)


015

02

025

03

035

04

pn pc p6n

p6c

p12n

p12c

Nor

mal

ized

spee

d


(c)





Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

110 1e5 2e5 3e5 4e5

Cumulated distance

CONCAS FF

(a)

CONCAS FF

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

Nor

mal

ized

pat

h le

ngth

13

12

11

10 5000 10000

Cumulated distance

t0

t0 mediant1


t0

t0 mediant1


(b)



Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 0017

80

60

40

CAS FF CON

Forc

e inc

linat

ion

wrt

cup

(deg

)80

60

40

30 40 50

Cup inclination

(a)


P = 0014


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

(b)

Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e inc

linat

ion

wrt

cup

(deg

)


P = 079

80

60

40

80

60

40

30 40 50 CAS FF CON

CAS FF

Cup inclination

CONOverall fit

CAS FF fitCON fit

(c)

Figure 9 Continued



P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


















P = 034


0 10 20 30

140

120

100

80

60

Forc

e ant

ever

sion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)140

120

100

80

60


CAS FF fitCON fit

(d)






1199052









1199052





70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















70

60

50

400 20 40 60


Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60

0 20 40 60


(a)

70

60

50

400 20 40 60



Forc

e inc

linat

ion

wrt

cup

(deg

)

Forc

e ant

ever

sion

wrt

cup

(deg

)

140

120

100

80

60


CAS FF fitCON fit


CAS FF fitCON fit

(b)










1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















1199052



4 Discussion











5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of






















5 Conclusion




Acknowledgments


References





























































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of







































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of






































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















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