Journal of Orthopaedics 13 (2016) 171176

Contents lists available at ScienceDirect

Journal of Orthopaedics
journal homepage: www.elsevier.com/locate/jor

Original Article

Gait analysis and hip extensor function early post total hip
replacement
Grainne Colgan a,*, Mike Walsh b, Damien Bennett b, John Rice a, Timothy OBrien b
a
AMNCH, Tallaght, Dublin 24, Ireland
b
Central Remedial Clinic, Clontarf, Dublin 3, Ireland

A R T I C L E I N F O A B S T R A C T

Article history: Objective: The purpose of this study was to systematically evaluate the sagittal kinematic and kinetic gait
Received 20 January 2016 patterns in patients in this early post-operative period, to describe them and to better understand the
Accepted 6 March 2016 deciencies in that gait pattern that may help to develop targeted rehabilitation strategies.
Available online
Methods: This study evaluated early gait patterns in 10 patients with isolated unilateral hip
osteoarthritis who were post-operative for total hip replacement. Kinetic and kinematic assessments
Keywords: focusing on sagittal plane abnormalities were performed at 2 weeks pre-operatively and 8 weeks
Gait analysis
post-operatively.
Orthopaedics
Hip replacement
Results: Our results demonstrated that while clinical scoring for pain and functional ability signicantly
Post-operative improved post-operatively, as did clinical assessment of range of motion passively, this did not translate
to the degree of dynamic improvement in gait. Step length and stride length did not improve
signicantly. Lack of hip extension in terminal stance associated with excessive anterior pelvic tilt
persisted and was associated with a worsening in hip extensor power post-operatively.
Conclusion: Based on our results, post-operative rehabilitation programmes should include extensor
muscle exercises to increase power and to retain the operative gain in passive range of motion, which
would help to improve gait patterns.
2016 Prof. PK Surendran Memorial Education Foundation. Published by Elsevier, a division of Reed
Elsevier India, Pvt. Ltd. All rights reserved.

1. Introduction hip exion contractures, with resultant loss of hip extension, have
been shown to recur up to 1 year after total hip replacement, and is
Osteoarthritis (OA) of the hip causes alteration in normal probably due to a combination of factors, e.g. persistent muscle
kinematic patterns particularly in the sagittal plane.1,6,7,9 This weakness, scar tissue formation and learned gait patterns though
may be primarily due to pain, a decreased range of motion because the exact pathogenesis is unknown.10,11,29 Recent outcome studies
of contractures or a combination of both. Total hip replacement have shown that post-operative range of hip motion correlates
surgery (THR) is one of the most successful surgeries, and provides strongly with functional outcome.35,36 The purpose of this study
symptomatic relief for patients with painful osteoarthritis.24 was to systematically evaluate the sagittal kinematic and kinetic
Despite this huge gain in functional ability and a subjective gait patterns in patients in this early post-operative period, to
improvement in walking ability, gait patterns in patients describe them and to better understand the deciencies in that gait
undergoing THR improve, but rarely achieve normality.57,10 Many pattern that may help to develop targeted rehabilitation strategies.
gait analysis studies have shown that gait patterns remain
abnormal in the long term and are comparable to pre-operative 2. Methods
gait.9,12,1719 Foucher et al. demonstrated that pre-operative gait
parameters were strong predictors of some post-operative gait 2.1. Patient selection and procedure
parameters.8 Range of motion was improved following THR, but in
many cases remained less than normal. It is important to note that Inclusion criteria for the study were patients with isolated
unilateral painful hip osteoarthritis, with no signicant medical
problems (ASA grade I & II) who were awaiting a total hip
* Corresponding author. Tel.: +353 877720822. replacement in Adelaide and Meath, incorporating the National
E-mail address: gcolgan@rcsi.ie (G. Colgan). Childrens Hospital (AMNCH) Tallaght.32,34 Exclusion criteria

http://dx.doi.org/10.1016/j.jor.2016.03.005
0972-978X/ 2016 Prof. PK Surendran Memorial Education Foundation. Published by Elsevier, a division of Reed Elsevier India, Pvt. Ltd. All rights reserved.
172 G. Colgan et al. / Journal of Orthopaedics 13 (2016) 171176

included patients with: contralateral hip pathology, contralateral 3. Results

hip replacement, knee pathology, neurological impairment of the
lower limbs, leg length discrepancy in a lower limb segment other 3.1. Patient demographics
than the pathological hip and xed spinal deformity, as these
factors would all have an affect on gait independent of hip The mean age was 55.4 (4371), M:F 1:1 and mean BMI 27.1
pathology. Case notes for all patients on the AMNCH waiting list (range, 22.731.8). Nine out of ten patients had moderate/severe
were reviewed and all patients who met the inclusion/exclusion OA in their affected hip (Table 1). The ten patients fully completed
criteria were invited to participate. A cohort of ten patients were all aspects of the study, and there were no post-operative
identied and contacted. Participation was voluntary, and complications that may have affected the results. Repeat post-
informed consent was obtained in each case. operative assessments were performed at 8 weeks, and all patients
Patients were assessed 2 weeks pre-operatively and 8 weeks were independently mobile at that stage. Post-operative leg length
post-operatively over a 4-month period. A thorough clinical discrepancy ranged from 26 mm to +5 mm, with a mean of
examination was conducted, using a goniometer to determine 2.5 mm.
joint range of motion for all lower limb joints and presence of
contractures. Manual muscle strength testing was also tested and 3.2. Functional outcome scoring
documented (strength classied on the Medical Research Council
Scale, graded 0 = no contraction to 5 = normal).33 Radiological Table 2 shows the functional scores. There was a statistically
examination included AP pelvis X-ray to determine grade of OA signicant improvement in mean functional outcome based on
using Kellgren and Lawrence scale, and CT scanography to physical component of SF-36v2 scoring, and for the components of
accurately measure for any leg length discrepancy.12 Self-assess- pain, function and range on motion, but not deformity on Harris
ment questionnaires were completed to give an objective measure Hip Scoring.
of function SF-36v2 and Harris Hip Score (HHS).34
Three-dimensional lower limb gait analysis was performed in 3.3. Clinical range of motion
the Gait Laboratory Central Remedial Clinic (CRC), Clontarf using
3 CODA MPX30 motion analysers (Charnwood Dynamics Limited, Pre-operatively, there was marked decreased range of motion
Leicestershire, England). Twenty-four surface mounts, consisting in the affected hip of all patients (Table 3). Nine of the ten patients
of markers in each three-dimensional plane (coded LEDs) were had a xed exion deformity (FFD) contracture pre-operatively.
applied to the bony sites of each of the lower limbs, according to Mean 158 ( 48 to 308). In all patients post-operatively there was
the Bell Hip model, which allows markers to be seen laterally.13 no xed exion contracture apparent on clinical examination, and
Markers were applied by the same investigator pre- and post- all could achieve active hip extension to neutral, at least (Table 3).
operatively. The pre-calibrated system captures the infrared light This improvement was statistically signicant (p = 0.0001).
signal sequence from these markers, at a frequency of 200 Hz as
the patient walks on a 20 m walkway. Patients were requested to 3.4. Temperospatial parameters
refrain from using analgesics on the day of the assessment. Static
and dynamic foot forces were recorded using Kistler piezo- Pre-operatively the walking velocity, cadence and step length
electric footplates, embedded in the walkway (Kistler Instru- were all reduced, compared to normal ranges. Though there was
ments Ltd.) and subsequent joint forces and moments were
calculated using inverse dynamic equations. Kinematic and Table 1
kinetic patterns of the pelvis, hip, knee and ankle joints of the Radiological grade of OA.
lower limbs were therefore assessed. Measuring three successive Kellgren & Lawrence grade 1 2 3 4
gait cycles to improve the accuracy and objectivity of the No of patients 1 1 6 2
measurements by ensuring reliability and determining repeat-
ability for each patients specic gait pattern minimized Table 2
variability in the group. Data from a single representative cycle Mean functional scores.
was retrieved for each patient and results produced were intra-
Pre-operative Post-operative Change in P value
subject ensemble averages. mean score mean score mean score
All patients had THR surgery performed through an ante-
SF-36 v2 PCSa 35.05 50.06 15.01 <.001
rolateral approach with half receiving a cemented Charnley THR
SF-36 v2 MCSb 49.7 55.67 5.97 .10
(DePuyTM) and half an uncemented Plasma cup/Bicontact stems Harris Hip Score 60.71 89.9 29.2 <.001
(Braun AesculapTM). Pain 23 43.2 20.2 <.001
Post-operatively, the patients received focused orthopaedic Function 31.5 38.5 7 .002
physiotherapist and were also instructed on a home exercise Deformity 2.8 3.6 0.8 .17
Range of motion 3.31 4.58 1.27 .002
programme to include joint ROM exercises and abductor muscle
a
strengthening. The patients were reassessed clinically and Physical component score.
b
Mental component score.
radiologically and self-assessment forms were repeated. Gait
analysis was repeated and the results compared to assess the Table 3
changes in the kinematic and kinetic patterns following total hip Analysis of range of motion results affected hip.
replacement. The results were further compared to a database of
Pre-operative Post-operative P value
age- and sex-matched controls. mean mean

Hip extension (8) 15.0 1.80 <.001

2.2. Statistical analysis
Hip exion (8) 82.7 94.3 .002
Hip internal rotation in exion (8) 1.7 10.6 <.001
Paired t-tests were used to test for differences between pre- Hip external rotation in exion (8) 6.7 21.6 <.001
operative and post-operative variables for the affected and Hip abduction (8) 14.71 19.85 .05
unaffected limbs. Statistical analyses were performed using SPSS1 Hip adduction (8) 6.01 15.20 <.001

13.0. P values <0.05 were considered signicant. P < .05 with 95% CI.
 G. Colgan et al. / Journal of Orthopaedics 13 (2016) 171176 173

Table 4
Analysis of temperospatial parameters affected hip.

Normala Pre-operative mean Post-operative mean Change in mean score P value

Gait cycle time (s) 1.01 1.12 1.07 0.05 .24

Cadence (Step/min) 119.9 108.38 112.07 3.7 .31
Step length (m) 0.73 0.586 0.614 0.028 .10
Stride length (m) 1.46 1.175 1.237 0.062 .07
Walking velocity (m/s) 1.46 1.091 1.171 0.08 .12
Percentage stance 59.9 60.42 59.84 0.58 .43
Percentage single limb support 40.2 36.3 37.76 1.46 .27

P < .05 with 95% CI.

a
CRC Laboratory normal.

Table 5
Comparative analysis of temperospatial parameters.

Pre-operative Post-operative

Affected side Unaffected side P value Affected side Unaffected side P value

Step length (m) 0.586 0.590 .76 0.614 0.62 .70

Percentage stance 60.42 63.7 .02 59.84 62.24 .02
Percentage single limb support 36.3 39.67 .02 37.76 40.16 .02

P < .05 with 95% CI.

Table 6
Summary gait kinematic and kinetic parameters pre- and post-operatively affected hip.

Normal Pre operative mean Post operative mean Change in mean P value*

Maximum anterior pelvic tilt (8) 9.21 20.08 16.62 3.83 .07
Minimum anterior pelvic tilt (8) 4.4 11 7.75 3.25 .12
Pelvic tilt range 4.8 9.08 8.50 0.58 .68
Max hip exion (8) 33.4 34.85 29.21 5.64 .08
Max hip extension in stance (8) 8.95 13.21 0.49 12.72 <.001a
Hip range 42.4 21.63 29.42 7.79 <.001a
Max hip extensor power (W/kg) 0.96 0.4761 0.32 0.14 .3
Max hip exor power (W/kg) 0.92 0.32 0.47 0.15 .1
Knee exion (8) 64.6 55.55 53.31 2.24 .59
Knee extension (8) 0.84 0.29 4.34 4.62 <.001a
Knee range 65.4 55.26 57.65 2.38 .46
Ankle dorsiexion (8) 13.87 14.45 14.09 0.36 .9
Ankle plantarexion (8) 24.25 16.35 16.25 0.1 .92
Ankle range 38.12 30.8 30.35 0.55 .88

The italic values represent the numerical difference between the pre- and post-operative mean.
*
P-value is pre- compared to post-operative results.
a
Signicant difference <.05 between pre- and post-operative mean.

improvement in all variables post-operatively, this was not clinical improvement in passive hip extension and resolution of the
statistically signicant (Table 4). Step length can vary between FFD. Excessive anterior tilt also improved post-operatively but was
affected and unaffected side, i.e. with an antalgic gait. However, still abnormal (16.628) reecting the persistent lack of hip
symmetry ratio of step length between affected and unaffected extension post-operatively. Kinetic assessment showed that while
side showed no differences pre- or post-operatively (Table 5) hip extension improved overall post-operatively, hip extensor power
though the percentage stance duration was signicantly higher for did not improve. In fact, hip extensor power dis-improved during
the unaffected limb pre-operatively (63.7 versus 60.42, p = 0.022). early stance compared to pre-operative measures (Figs. 1 and 2).
There was modest improvement in single limb support post-
operatively on the affected side (36.3% versus 37.76%), but there 4. Discussion
was still a statistically signicant difference between the affected
and unaffected limb for percentage stance (59.84% versus 62.24%, Many studies have evaluated and described the persisting
p = 0.016), and percentage single limb support (37.76% versus abnormalities in gait patterns at up to two years post-operatively.
40.16%, p = 0.016), indicating residual asymmetry between the The purpose of this study was to evaluate gait patterns and muscle
limbs despite clinical improvement in pain. function in the very early post-operative period in an attempt to
compare clinical assessment with objective gait analysis param-
3.5. Gait kinematics & kinetics eters. Eight weeks were chosen as this was the earliest period that
patients were likely to be walking without the use of crutches or
The key kinematic and kinetic data is summarized in Table 6, and post-operative analgesics, which could have altered results.
relevant graphs are shown in Figs. 1 and 2. The most signicant pre- This study demonstrated a clinical improvement in range of
operative nding was lack of hip extension and excessive anterior motion in the affected hip in all planes eight weeks post-operatively,
pelvic tilt seen in terminal stance and pre-swing phases. While there but this improvement had not carried over into walking ability. All
was improvement post-operatively in sagittal hip kinematics in patients improved subjectively and objectively based on SF-36v2
terms of hip extension and hip range of motion, there was still a and HHS. Clinically, eight out of ten patients post-operatively
relative lack of hip extension in terminal stance (0.498), despite a had complete elimination of pain, and a statistically signicant
174 G. Colgan et al. / Journal of Orthopaedics 13 (2016) 171176

Fig. 1. Ensemble averages for pre-operative sagittal hip and pelvis kinematics and hip extensor moment and power in affected hip. Ensemble averages. Max/mon for
dataset. CRC Laboratory normal database results.

improvement in extension of the affected hip, yet the abnormality of Our ndings also reect those of other studies in terms of lack of
lack of hip extension persisted post-operatively during walking. This hip extension. Perron et al. suggested that the lack of hip extension
was associated with an increase in anterior pelvic tilt. was due to a decrease in step length, and was a learned pattern of
In an antalgic gait, the patient classically tries to minimize the gait, rather than due to a weakness of hip extensor muscles, but
amount of weight applied to the painful hip and the amount of time they did not assess clinical hip range of motion.1 Crosbie showed
that weight is applied. The result is a limp, a decreased single support that lack of hip extension in walking correlated with lack of clinical
time for the affected limb, a shortened step length for the range of motion and was speed-dependent.15 Hurwitz et al.
contralateral limb and an increased double support time. Calve showed decreased hip extensor moments associated with pain in
et al. proposed that this mechanism avoided stretching the joint patients with osteoarthritis rather than gait speed or dynamic hip
capsule and thus prevented pain.14 In keeping with other studies of range of motion. The authors felt that reduced moments reect
early gait following THR, this lack of terminal hip extension in late decreased muscle forces and decreased loads on the femoral
stance was associated with a decrease in hip extensor power and head in the absence of increased antagonistic muscle activity and
exor moments of force and a decrease in the energy developed at thus may be a pain-avoidance mechanism. However, they also
the hip in the sagittal plane during push-off despite subjective demonstrated asymmetry in step length.30 In contrast, this study
improvement in symptoms.10,11,22,26,27,29,30 Though this may be a found that despite a failure to extend the hip on the affected side
learned protective mechanism of the hip, it implies that pain is not during walking, there was no difference in step length, and no
the only factor affecting extension ability. The fact that hip extensor difference in symmetry ratio between the affected and unaffected
power actually decreased post-operatively despite improvement in side pre- and post-operatively. Assessment of temperospatial
both clinical range of motion and pain is important as it is potentially parameters showed no statistical differences between the affected
overlooked during routine post-operative assessment. Many phys- and unaffected side pre- or post-operatively for velocity, step
iotherapy rehabilitation programmes focus on coronal muscle length or cadence; however, the values were less compared to
strengthening i.e. abductor function but do not assess sagittal range normative data.2325,27,28 Though all parameters improved post-
and strength. Hip exion contractures have been shown to recur up operatively, the differences were not statistically signicant. This
to 1 year after surgery and are probably due to a combination of indicates a degree of symmetry between the limbs however,
factors e.g. persistent muscle weakness, learned gait patterns and there was a statistically signicant difference in percentage stance
scar tissue formation etc.10,11,21,29 Our study patients demonstrated time between the limbs both pre- and post-operatively. This
a persistent lack of hip extension during dynamic gait coupled with residual antalgic gait may be an avoidance mechanism to reduce
worsened hip extensor power post-operatively and we suggest this loading of the affected side, which persisted post-operatively
may be a possible the mechanism by which these contractures recur. despite resolution of pain and increased range of motion. Bennett
 G. Colgan et al. / Journal of Orthopaedics 13 (2016) 171176 175

Fig. 2. Ensemble averages for post-operative sagittal hip and pelvis kinematic and hip extensor moment and power in affected hip. Ensemble averages. Max/mon for
dataset. CRC Laboratory normal database results. Ensemble average kinematic gait cycle overlaid on normal band. Horizontal axis: percentage of gait cycle. 0 = initial
contact; 060 = stance phase; 60 = push-off; 60100 = swing phase.

et al. suggested that the range of motion in the unaffected hip may feel that the results obtained from this detailed study can be
be effectively reduced to maintain symmetry and improve walking condently attributed to the hip pathology. Our results suggest
ability.16 that gait patterns remain persistently abnormal post-operatively
Our patients were re-assessed at 8 weeks post-operatively, despite relatively normal clinical ranges of motion. This area
which is earlier than most studies. It has been shown that gait requires further study to develop early post-operative rehabilita-
parameters improve for up to 1 year post-operatively, so it is not tion programmes focusing on hip extensor power and gait
surprising that the abnormality of slower speed and decreased step training rather than traditional hip range of motion and stretching.
length were still present post-operatively.17,18,23 McCrory et al.
found that magnitude of peak hip forces was signicantly less in the Ethical approval
operated hip following THR, as was loading rate, impulse and stance
time, i.e. patients favoured their affected limb by avoidance of Ethical approval for the study was obtained from the Research
weight acceptance, despite being pain-free, they displayed features Ethics Committee of St James Hospital and the AMNCH, Tallaght.
of residual antalgic gait.20 They commented that the persisting
asymmetric limb loading after THR may be benecial in reducing the
Funding
biomechanical load on the prosthesis.27 In contrast, Shakoor et al.
suggested that biomechanical asymmetry post-operatively was
There was no source of external funding.
disadvantageous. They demonstrated persistent asymmetry of limb
loading in patients up to 2 years post THR specically noting a
higher peak external knee adduction moment, and peak medial Conicts of interest
compartment moment in the contralateral knee, which persisted
after surgery. They proposed this as the mechanism for which The authors have none to declare.
patients who undergo unilateral THR for OA are more likely to
require a contralateral Total Knee Replacement in the future.31 References

1. Perron M, Malouin F, Moffet H, McFadyen BJ. Three dimensional gait analysis in

5. Conclusion
women with a total hip arthroplasty. Clin Biomech 2000. 2000;5:504515.
2. Liang M, Cullen K, Larson M, Thompson M, Schwartz J, Fossel A. Cost effectiveness
We acknowledge that this study was limited by the small of total joint arthroplasty in osteoarthritis. Arthritis Rheum. 1986;29:937943.
number of participants, which may have implications for the 3. Rissanen P, Aro S, Slatis P, Sintonen H, Paavolainen P. Health and quality of life
before and after hip or knee arthroplasty. J Arthroplasty. 1995;10:169175.
generalisability of our results. However, our group of participants 4. Maloney WJ, Keeny JA, Leg length discrepancy after total hip replacement. J
was a uniform cohort with only single joint osteoarthritis, and we Arthroplasty. 2004;19(4 (Suppl. 1)):108110.
176 G. Colgan et al. / Journal of Orthopaedics 13 (2016) 171176

5. Loizeau J, Allard P, Duhaime M, Landjerit B. Bilateral gait patterns in subjects tted 21. Stanseld BW, Nicol AC. Hip joint contact forces in normal subjects and subjects
with a total hip prosthesis. Arch Phys Med Rehabil. 1995;76(June (6)):552557. with total hip prostheses: walking and stair and ramp negotiation. Clin Biomech
6. Kyriazis V, Rigas C. Temporal gait analysis of hip osteoarthritic patients operated (Bristol Avon). 2002;17(February (2)):130139.
with cementless hip replacement. Clin Biomech (Bristol Avon). 2002;17(May 22. Mattsson E, Brostrom LA, Linnarsson D. Walking efciency after cemented and
(4)):318321. noncemented total hip arthroplasty. Clin Orthop Relat Res. 1990;(May (254)):
7. Wykman A, Olsson E. Walking ability after total hip replacement. A comparison of 170179.
gait analysis in unilateral and bilateral cases. J Bone Joint Surg Br. 1992;74(January 23. Elble RJ, Thomas SS, Higgins C, Colliver J. Stride-dependent changes in gait of older
(1)):5356. people. J Neurol. 1991;238(February (1)):15.
8. Foucher KC, Hurwitz DE, Soomekh D, Andriacchi TP, Rosenberg AG, Galante JO. 24. Prince F, Corriveau H, Hebert R, Winter DA. Gait in the elderly. Review article. Gait
Factors inuencing variation in gait adaptations after total hip arthroplasty. Gait Posture. 1997;(5):128135.
Posture. 1998;7(March (2)):158159. 25. Oberg T, Karsznia A, Oberg K. Basic gait parameters: reference data for normal
9. Tanaka Y. Gait analysis of patients with osteoarthritis of the hip and those with subjects, 1079 years of age. J Rehabil Res Dev. 1993;30(2):210223.
total hip arthroplasty. J Jpn Orthop Assoc. 1993;67:100113. 26. Long WT, Dorr LD, Healy B, Perry J. Functional recovery of noncemented total hip
10. Paul JP. Gait analysis. Ann Rheum Dis. 1989;48:179181. arthroplasty. Clin Orthop Relat Res. 1993;(March (288)):7377.
11. Paul JP. Strength requirements for internal and external prostheses. J Biomech. 27. Miki H, Sugano N, Hagio K, et al. Recovery of walking speed and symmetrical
1999;32(April (4)):381393. movement of the pelvis and lower extremity joints after unilateral THA. J Biomech.
12. Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum 2004;37(April (4)):443455.
Dis. 1957;16:494502. 28. Murray MP, Brewer BJ, Gore DR, Zuege RC. Kinesiology after McKeeFarrar total hip
13. Newman C, Walsh M, OSullivan R, et al. The characteristics of gait in Charcot replacement. J Bone Joint Surg. 1975;57A:33742.
Marie-tooth disease types I and II. Gait Posture. 2007;26(June (1)):120127. 29. Shimada T. Factors affecting appearance patterns of hip exion contractures
14. Calve J, Galland M, DeCagney R. Pathogenesis of the limp due to coxalgia. J Bone and their effects on postural and gait abnormalities. Kobe J Med Sci. 1996;42:
Joint Surg. 1939;21:1225. 271290.
15. Crosbie J, Vachalathiti R. Synchrony of pelvic and hip joint motion during walking. 30. Hurwitz DE, Hulet CH, Andriacchi TP, Rosenberg AG, Galante JO. Gait compensa-
Gait Posture. 1997;6:237248. tions in patients with osteoarthritis of the hip and their relationship to pain and
16. Bennett D, Humphreys L, OBrien S, Kelly C, Orr JF, Beverland DE. Gait kinematics of passive hip motion. J Orthop Res. 1997;15(July (4)):629635.
age-stratied hip replacement patients a large scale, long-term follow-up study. 31. Shakoor N, Hurwitz DE, Block JA, Shott S, Case JP. Asymmetric knee loading
Gait Posture. 2008;28(August (2)):194200. in advanced unilateral hip osteoarthritis. Arthritis Rheum. 2003;48(June (6)):
17. Murray MP. Studies of the functional performance of patients before and after total 15561561.
joint replacement. Int J Rehabil Res. 1979;2(December (4)):543. 32. Saklad M. Grading of patients for surgical procedures. Anesthesiology. 1941;2:
18. Wall JC, Ashburn A, Klenerman L. Gait analysis in the assessment of functional 281284.
performance before and after total hip replacement. J Biomed Eng. 1981;3(April 33. Medical Research Council. Aids to the investigation of the peripheral nerve system.
(2)):121127. London: Her Majestys Stationery Ofce; 1975:12.
19. Murray MP, Brewer BJ, Zuege RC. Kinesiologic measurements of functional per- 34. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures:
formance before and after McKeeFarrar total hip replacement. A study of thirty treatment by mold arthroplasty. J Bone Joint Surg. 1969;51A:737755.
patients with rheumatoid arthritis, osteoarthritis, or avascular necrosis of the 35. Davis KE, Ritter MA, Berend ME, Meding JB. The importance of range of motion after
femoral head. J Bone Joint Surg Am. 1972;54(March (2)):237256. total hip arthroplasty. Clin Orthop Relat Res. 2007;465(December):180184.
20. McCrory JL, White SC, Lifeso RM. Vertical ground reaction forces: objective 36. Johansson HR, Bergschmidt P, Skripitz R, Finze S, Bader R, Mittelmeier W. Impact of
measures of gait following hip arthroplasty. Gait Posture. 2001;14(October preoperative function on early postoperative outcome after total hip arthroplasty. J
(2)):104109. Orthopaed Surg. 2010;18(April (1)):610.