Hip resurfacing generates a more physiological gait than total hip replacement: A case-control study

Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

Contents lists available at ScienceDirect

Orthopaedics & Traumatology: Surgery & Research journal homepage: www.elsevier.com

Original article

Hip resurfacing generates a more physiological gait than total hip replacement: A case-control study Cedric Maillot a , Edouard Auvinet a , Ciara Harman b , Justin Cobb a , Charles Rivière a,b,∗ a b

Laboratory Block, MSK Lab, Imperial college London, White City Campus, W12 0BZ London, United Kingdom South West London Elective Orthopaedic Centre, Dorking road, KT18 7EG Epsom, United Kingdom

a r t i c l e

i n f o

Article history: Received 7 June 2019 Accepted 4 December 2019 Keywords: Hip replacement Hip resurfacing Gait analysis Symmetry index Kinematic alignment

a b s t r a c t Background: Restoration of the constitutional joint anatomy after hip replacement favours physiological peri-articular soft-tissue tension and kinematics, and is likely to be functionally beneficial. Hip resurfacing (HR) and conventional total hip replacement (THR) are two different options for replacing degenerated hips, and are likely to result in different anatomical reconstruction. We initiated this study to investigate the differences in gait performance between these two prosthetic options, and aimed to answer the following questions: (1) does HR result in better restoration of the frontal hip anatomical parameters, (2) and generate a more physiological gait compared to THR? (3) Does the quality of the anatomical restoration after THR influence gait performance? Hypotheses: Our hypothesis was that a better anatomical restoration using HR versus THR would produce more physiological (symmetric) gait. Methods: We retrospectively reviewed 52 patients who had unilateral primary osteoarthritis successfully treated by replacement (40 THRs and 12 HRs). Hip anatomical parameters were measured on standing pelvic radiographs on both the prosthetic and the contralateral healthy hips. Patients undertook gait assessment under both normal and stress conditions at a mean follow-up of 14 months (7 to 16 months). Gait performances were compared between HR and THR, and the relationship between gait performances and quality of frontal anatomical restoration (estimated on radiograph) were assessed. Results: Compared to the native contralateral side, the HR procedure tended to decrease all independent anatomical radiographic parameters with the exception of the vertical centre of rotation offset, whilst the THR procedure tended to increase them; the difference between HR and THR was only statistically significant for femoral offset and global horizontal offset (increased after THR while reduced after HR). Only 50% of THR and 25% of HR procedures closely anatomically (±15%) recreated both global horizontal offset and global vertical offset. Under normal conditions (normal walking speed and flat ramp), the gait was fairly symmetric for both the HR and the THR patients with a symmetry index of 0.62% and 3.14% respectively. At high walking speed (stress conditions), the symmetry index degraded for both groups, but the gait remained more symmetric in the HR group (2.09%), compared to the THR group (5.74%); nevertheless, the difference remained not statistically significant (p = 0.159). We were unable to detect any significant relationship between gait performances and radiographically measured hip frontal anatomical parameters. Discussion/conclusions: HR procedure is more consistent than conventional THR in generating a more physiological gait under stress conditions. Radiographic estimation of the quality of the frontal anatomical hip restoration is of poor value to predict gait performances of THR patients. Level of evidence: III – retrospective case-control study with prospective data collection. © 2020 Elsevier Masson SAS. All rights reserved.

∗ Corresponding author at: Laboratory Block, MSK Lab, Imperial college London,White City Campus, W12 0BZ London, United Kingdom. E-mail address: [email protected] (C. Rivière). https://doi.org/10.1016/j.otsr.2019.12.020 1877-0568/© 2020 Elsevier Masson SAS. All rights reserved.

528

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

1. Introduction Hip replacement, either hip resurfacing (HR) or conventional total hip replacement (THR), is a successful procedure, which often significantly improves patients’ quality of life. Usually, the Oxford Hip and EQ5D index scores at 3 months follow-up after hip replacement are above 36 (maximum = 48) and 0.8 (maximum = 1), respectively [1,2]. As a result of the good long-term lifespan of hip implants and the development of bone-preserving component designs, hip replacement is increasingly performed at a younger age when patients are still active and have high expectations [3,4]. The better the anatomical reconstruction during hip replacement, the more the surrounding soft-tissue balance and prosthetic hip kinematics are likely to be close to physiological, and the functional performance optimal [5–10]. Intra-operative technological assistance (e.g. computer assisted surgery, robotics, custom instruments), implant modularity (e.g. modular head/neck, multiple head diameters), bone-preserving femoral components (e.g. hip resurfacing, neck sparing short stem), and kinematic alignment technique for implanting hip components [11,12] have been developed to improve the hip anatomical restoration during THR implantation. Compared to conventional techniques for implanting THR components, HR inherently aims to preserve the unique individual proximal femur tri-dimensional anatomy. This, in addition to being bone-preserving, may explain the excellent functional outcomes of HR [13–15]. Functional benefits from anatomical hip restoration when performing prosthetic replacement are probable but remain difficult to demonstrate with patient reported outcome measurements (PROMs); this may be partly explained by their high ceiling effect [16–18]. A more sophisticated way to assess functional performances between either different implant designs or various techniques for aligning prosthetic components is to perform a gait analysis and compare the symmetry index (SI). Treadmill gait analysis enables a quantitative and objective functional assessment under normal (normal speed on flat ramp) and stress conditions (high speed walking, declined and inclined ramp); this makes the functional assessment less sensitive to the ceiling effect associated with typical patient reported outcome measures [19]. The available evidence suggests that the gait is relatively symmetric for healthy subjects (SI = 4%) [20], but this degrades in osteoarthritic disease [21], with only a partial correction after hip replacement [22]. These issues were incompletely investigated in the literature, therefore we initiated this study to compare the gait performances between HR and THR patients, and aimed to answer the following questions: • does HR result in better restoration of the frontal hip anatomical parameters compared to THR? • Does HR generate a more physiological gait compared to THR? • Does the quality of the anatomical restoration after THR influence gait performance? Our hypothesis was that a better anatomical restoration using HR versus THR would produce more physiological (symmetric) gait. 2. Patients and methods 2.1. Study design and population We performed a retrospective, single-centre, single-surgeon, pilot study. In September 2016, after screening our prospectivelygathered database, we included 52 prosthetic adult patients (40 THRs and 12 HRs) who had had a successful unilateral hip replacement (satisfied patients with Oxford Hip Score = 44) between 2011

Table 1 Demographic and clinical data for the THR and HR groups.

Age Sex (M/F) BMI Oxford Hip Score

THR

HR

p-value

64 (61; 69) 14/26 24.57 (22; 27) 46 (45; 48)

58 (55; 63) 9/3 25.90 (25; 27.5) 46 (44; 47)

0.022a 0.015a 0.213 0.503

All variables are expressed as median (lower quartile, upper quartile). THR: total hip replacement; HR: hip resurfacing. a Statistically significant difference.

and 2014 for severely debilitating primary hip osteoarthritis, had a native healthy contralateral hip, had no comorbidity liable to affect their functional performance (e.g. lower limb osteoarticular disorders or joint replacement, severe obesity, sagittal spinal imbalance, cardiac or neuromuscular disorder), had undertaken a gait analysis at a minimum of 7 months post-surgery, and had complete demographics, functional, radiographic, and gait data. All data were prospectively collected, at the exception of the radiographic measurements. Median age and BMI for the whole cohort was 63 years (from 57 to 67), and 25.4 kg.m−1 (from 22.73 to 27.2), respectively. The demographic and functional data for HR and THR groups are displayed in Table 1: there were significant difference in terms of sex and age between groups. A sample size was not calculated, as the effect size of HR and THR on the gait symmetry index was unknown at the time we designed the study. All participants gave their written consent, and ethical approval (10/HO807/101) was gained before the study started. 2.2. Surgical procedure Forty patients were conventionally implanted with a THR implant (FurlongTM Hip System using either conventional [6A] or short EVO [34A] FurlongTM stems; JRI, Sheffield, England) and twelve patients with a Birmingham Hip ResurfacingTM (Smith and Nephew, Memphis, TN). Surgeries were all performed with manual instrumentation, through a posterior approach, and with repair of the capsule and external rotators at the end of the procedure. THR patients were implanted with either 32 or 36 mm heads, and their components were systematically aligned as follow: acetabular cup inclined 40◦ and anteverted 15◦ relative to the anterior pelvic plane, femoral stem anteverted 10◦ to 15◦ relative to the posterior condylar line. 2.3. Gait assessment Subjects performed a gait analysis under both normal and stress conditions at a median of 14 months (7 to 16 months) post-surgery on an instrumented treadmill (Kistler Gaitway; Kistler Instrument Corporation, Amherst, NY), using a standardized published method [23]. After a period of familiarisation, the patients had their gait recorded for different walking speed conditions (3.5 km/h followed by sequential incrementation of 0.5 km/h until the patient selfdetermined their top walking speed) and ramp inclinations (flat surface, 5◦ and 10◦ incline, then 5◦ decline). Six kinetic ground reaction force parameters were measured for both the prosthetic and the contralateral native hips of each patient: weight acceptance (heel strike) peak force and peak time, mid support force and time, push off (toe off) peak force and peak time. The data analysis was performed using custom software written using Matlab R2015b. 2.4. Radiographic study Each patient had a standing antero-posterior pelvis X-ray done at 6 weeks post-surgery. Images were imported as DICOM files into OsiriX MD 7.0 image processing software in order to make

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

529

Table 2 Ratio prosthetic hip/healthy contralateral hip of independent radiographical parameters for the THR and HR groups. Total hip replacement (n = 40) Ratio vertical centre of rotation (VCOR) – (%) Ratio horizontal COR (HCOR) – (%) a Ratio femoral offset (FO) – (%) Ratio limb-length (LL) – (%) a Ratio global horizontal offset (GHO) – (%) Ratio global vertical offset (GVO) – (%)

Fig. 1. Radiographical parameters assessed for the operated and non-operated hip on supine antero-posterior pelvis postoperative radiographs. 1: vertical centre of rotation (VCOR) as perpendicular distance from the COR of the hip to the interteardrop line; 2: acetabular offset = horizontal COR (HCOR) as distance between the vertical COR line and the teardrop; 3: femoral offset (FO) as perpendicular distance from the centre of rotation to the femoral shaft line, and; 4: limb-length (LL) as perpendicular distance from the teardrop to the apex of the lesser trochanters. Two combined parameters were calculated: global horizontal offset (GHO = 2 + 3) was defined as the sum of femoral offset (FO) + acetabular offset (HCOR); and global vertical offset (GVO = 4-1) as the difference in Limb-length (LL) – vertical centre of rotation (VCOR).

the following measurements (Fig. 1): vertical (VCOR) and horizontal (HCOR) centre of rotation offsets, femoral offset (FO), and limb-length (LL). In addition to the measured parameters, two combined parameters were calculated: the global horizontal offset (GHO = FO + HCOR) and the global vertical offset (GVO = LL − VCOR). 2.5. Statistical analysis We pooled together the gait acquisition results for normal and fast speed according to published cut off values (around 6 km/h and 5.5 km/h for men and women, respectively, with some variations based on the age) [24]. Gait data were normalized for weight and height in order to enable cross-group comparison. We calculated the gait symmetry index (SI) between the prosthetic and the contralateral native limb for weight acceptance peak force, mid support force and push off peak force by using the equation (1) “SIX = (XProsthetic − XNativ CL )/ [0.5(XProsthetic + XNativ CL )] × 100” [15], where XProsthetic is a gait variable recorded for the prosthetic side and XNative CL is the corresponding variable for the contralateral native hip. Values closer to zero indicated a perfectly symmetrical gait. To account for the absence of X-ray calibration, we computed the “prosthetic/native contralateral” ratio for each radiographical biomechanical parameter by using the equation (2) “RatioY = [(Yprosthetic − YNative CL )/YNative CL ] × 100”, where YProsthetic and YNative CL represent the radiographic variable recorded for the prosthetic and the native contralateral limb, respectively. The RatioY values represent the percentage difference between the prosthetic and the reference native contralateral measures, with the zero-value indicating a perfect symmetry between them. A positive value indicates a prosthetic measure is superior than the native contralateral one. In order to further assess the influence of altering the hip anatomy on the gait performances, we classified the peri-prosthetic soft-tissue balance into 6 different groups, as illustrated in Fig. 2, by combining the RatioGHO and RatioGVO . We selected a threshold of 15% of variation between prosthetic and native contralateral

7.58 (−9.1; 27.7) 0 (−4; 2,6)

Hip resurfacing (n = 12) 12.92 (−6.8; 25.3) −2.02 (−6.3; 2.6)

4.56a (−1.5; 13.4)

−8.01a (−13.4; 3.3)

0 (−3.1; 3.3)

−2.8 (−13.9; 3.8)

3.03a (−0.7; 8.1) −4.99 (−17.4; 8.9)

−3.96a (−10.4; 0) −13.47 (−41.5; 15.5)

All variables are expressed as median (lower quartile, upper quartile). The ratio values obtained are the percentage of variation of prosthetic radiological variables using the healthy contralateral side as a reference. Values closer to zero indicated a perfectly symmetrical radiological parameter. THR: total hip replacement; HR: hip resurfacing. a Significant difference between THR and HR.

parameters (GHO or GVO) as this has been reported to be the minimum value having a biomechanical and clinical influence [25,26]. All the variables were presented as median (lower quartile, upper quartile). The radiographical and gait parameters for THR and HR groups under every gait condition were compared by using the Mann Whitney U test, and the data from each gait condition compared by using the Kruskal-Wallis test. Statistical significance (p-value) for these tests was set at 0.05. Each measured radiographic parameter (RatioY and each group of peri-prosthetic soft-tissue tension) was correlated with the gait (SIX ) parameters for each gait condition (flat surface – normal speed [FN], flat surface – fast speed [FF], incline – normal speed [I], and decline – normal speed [D]), by using the Pearson correlation test. Statistical significance (p-value) of the Pearson coefficients was adjusted at 0.03 to correct for multiple analyses. Statistical analysis was performed using IBM SPSS, version 21. 3. Results The RatioY for each radiographical parameter and the distribution of patients amongst groups of “prosthetic soft-tissue tension” are illustrated in Tables 2 and 3, respectively. Compared to the native contralateral side, the HR procedure tended to decrease all independent anatomical radiographic parameters with the exception of the VCOR, whilst the THR procedure tended to increase them; the difference between HR and THR was only statistically significant for FO and GHO (Table 2). Whilst both procedures reproducibly restored the native HCOR, there was more variability in the restoration of the FO (Table 2). Regarding the combined parameters (Table 3), 0% (0/12) and 25% (3/12) of HR procedures, and 10% (4/40) and 18% (7/40) of THR procedures, significantly (>15% compared to the healthy contralateral hip) increased the GHO and GVO, respectively. Only 50% of THR and 25% of HR procedures closely anatomically (±15%) recreated both GHO and GVO. The SIx and average gait kinetic parameters for HR and THR patients are illustrated in Table 4 and Fig. 3, respectively. Both HR and THR patients had a relatively symmetric gait under normal conditions (normal walking speed and flat ramp), with a symmetry index of 0.62% and 3.14% respectively. Knowing that healthy people may have a symmetry index of up to 4%, 17/40 (42.5%) of THR patients and 5/12 (42%) of HR patients were under this threshold. Regarding stress conditions, increasing the walking speed was more deleterious on the symmetry of the gait than inclining the ramp for both the HR and THR groups. At high walking speed, the

530

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

Fig. 2. Soft-tissue balancing. GHO: global horizontal offset; GVO: global vertical offset.

Table 3 Distribution of patients according to composite radiological hip parameters. Ratio global horizontal offset

Ratio global vertical offset <−15% Restored >15%

<−15%

Restored

>+15%

None None None

15 patients: HR 6/12 (50%)/THR 9/40 (22.5%) 23 patients: HR 3/12 (25%)/THR 20/40 (50%) 10 patients: HR 3/12 (25%)/THR 7/40 (17.5%)

3 patients: THR 3/40 (7.5%) 1 patient: THR 1/40 (2.5%) None

THR: total hip replacement, HR: hip resurfacing.

Table 4 Gait symmetry index (SI) between prosthetic and healthy contralateral side under different gait conditions for the THR and HR groups. Groups

Speed

Plan

SI Weight acceptance peak force

SI Weight acceptance peak time

SI Mid support force

SI Mid support time

SI Push off peak force

SI Push off peak time

THR

Normal Fast Normal

Flat

−3.14 (−5.7; 1.0) −5.74a (−7.1; −1.3) −1.79a (−3.5; 1.7) −0.54a (−3.4; 1.4) −1.28a (−4.1; 0.5) −0.62 (−2.9; 1.7) −2.09a (−5.1; 0.8) −1.53a (−3.6; 1.0) −0.32a (−1.3; 0.4) 2.04a (−1.4; 2.8)

4.8 (−0.6; 10.4) 4.03a (−3.4; 7.3) 3.03 (−2.4; 10.2) 3.33a (−2.0; 12.0) −4.59a (−8.6; 8.5) 1.04 (−3.5; 7.0) −3.01a (−7.0; 0.2) −1.69 (−3.8; 0.4) 0.42 (−3.4; 6.9) 4.52a (−8.2; 9.8)

1.7 (−1.1; 4.7) 2.51a (−1.1; 6.4) 2.03a (−0.1; 3.8) 1.02a (−0.9; 2.0) −0.34a (−1.5; 1.6) 0.07 (−2.2; 3.0) −2.62a (−12; 9.1) 1.15a (−2.4; 3.8) 1.48a (−2.7; 3.3) −0.39 (−3.3; 2.2)

−0.02 (−3.7; 3.9) −0.13 (−3.3; 1.7) −1.35a (−4.2; 3.1) −0.73a (−4.1; 5.9) −0.31a (−3.5; 3.8) −1.59 (−3.6; 0.8) −0.66 (−3.8; 4.0) −6.52a (−10; 0.5) −1.47a (−4.0; 2.6) −1.49a (−2.7; 3.8)

−1.05 (−3.7; 1.1) −2.04 (−3.1; −0.7) −1.5a (−4.2; 1.8) −1.9a (−5.5; 1.4) −1.92a (−3.7; 1.7) −0.79 (−2.0; 1.6) −0.46 (−2.0; 2.0) −0.37 (−4.2; 3.1) −1.21 (−3.6; 2.0) 2.07a (0.5; 3.4)

−0.73 (−2.6; 1.3) −1.16 (−3.7; 0.1) 0.01 (−4.3; 2.0) 0 (−4.2; 1.8) −1.24 (−7.2; 0.9) −1.31 (−2.2; 2.5) −0.63 (−3.2; 3.8) −2.02 (−3.1; −0.1) −0.42 (−4.9; 1.7) −0.16 (−0.9; 2.9)

HR

Normal Fast Normal

10◦ incline 5◦ incline Decline Flat 10◦ incline 5◦ incline Decline

All variables are expressed as median (lower quartile, upper quartile), no unit. The SI values obtained are the percentage of variation of prosthetic gait variables using the healthy contra-lateral side as a reference; values closer to zero indicate a perfectly symmetrical gait. THR: total hip replacement; HR: Hip resurfacing. a Statistically significant difference between normal speed on flat plane and other condition within THR and HR groups.

symmetry index degraded for both groups, but the gait remained more symmetric in the HR group, as illustrated by the SIx for weight acceptance at fast flat exercise being 2.09% and 5.74% for HR and THR patients (p = 0.159), respectively. The gait symmetry indices between soft-tissue tension groups under different gait conditions are illustrated in Table 5. We were unable to detect significant gait differences between THR patients having various estimated “peri-prosthetic soft-tissue balance” (Table 5). In addition, we were unable to detect any significant relationship between gait performances (SIX ) and radiographically measured hip frontal anatomical parameters (Table 6). 4. Discussion Our main findings are that HR procedure is more consistent than conventional THR in generating a more physiological gait under

stress conditions, and radiographical estimation of the quality of the frontal anatomical hip restoration is of poor value to predict gait performances of THR patients. We found the HR procedure mainly reduced the medial FO, while the THR procedure increased it, and the change in GHO after HR and THR procedures was mainly the consequence of change in FO. Our results are in line with those of Silva et al. [27], who compared 50 HR and 40 conventional THR patients; the authors found that HR and THR patients had prosthetic FOs that were respectively 8 mm reduced and 5 mm increased compared to the healthy contralateral hip. Difference in surgical techniques between HR and THR procedures may partly explain these findings. When performing HR, the medio-lateral positioning of the femoral component is determined by the location of the superior femoral neck cortico-cancellous junction; the frequently observed pistol grip deformity on the osteoarthritic hips of young patients eligible for HR may favour an excessively medial location

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

531

Fig. 3. This graph illustrates the average ground reaction force’s symmetric indexes (numerical scale) that were measured on total hip replacement (THR) and hip resurfacing (HR) patients during the stance phase at the weight acceptance, mid support, and push off. The closer the symmetric index is to zero, the more symmetric the prosthetic and healthy contralateral hips. Table 5 Gait symmetry index between soft-tissue tension groups under different gait conditions for the whole group. Speed

Plan

Gait symmetric index

Group B

Group C

Group D

Group E

p-value

Normal

Flat

Weight acceptance peak force Mid support force Push off peak force Weight acceptance peak force Mid support force Push off peak force Weight acceptance peak force Mid support force Push off peak force Weight acceptance peak force Mid support force Push off peak force Weight acceptance peak force Mid support force Push off peak force

−2.22 (−3.8; 0.4) 2.65 (−0.9; 3.5) −0.9 (−3.5; 0.8) −1.29 (−6.6;−0.5) 1.9 (−2.4; 6.4) −2.17 (−5.3;−0) −1.78 (−3.2; 1.6) 1.38 (−0.9; 5.6) 0.09 (−3.5; 3.1) −0.41 (−3.4; 1.5) 1.69 (−1.5; 2.6) −1.61 (−5.5; 2.2) −0.96 (−1.7; 2.7) 0.75 (−2.2; 2.1) 0.81 (−1.4; 1.7)

−3.56 (−6.7; 0.3) 1.76 (−1.5; 4.8) −1.34 (−3.6; 0.8) −6.45 (−8.2;−2) 4.27 (−4.3; 7.9) −1.7 (−3.2;−0.3) −3.15 (−5.8; 0.2) 0.94 (−1.1; 3.6) −1.46 (−4.6; 2) −0.68 (−4.3; 0.8) 1.35 (−0.7; 2.3) −1.19 (−4.1; 1.2) 2.04 (−1.3; 2.3) −0.34 (−0.5; 2.3) −1.92 (−3.6; 2.5)

0.37 (−1.5; 2.1) −1.02 (−3.4; 0.3) 1.12 (1.1; 2.4) −0.51 (−3.4; 2.3) −8.53 (−12.3;−4.7) 3.7 (1.7; 5.7) 1.99 (1.9; 2) 2.87 (2.8; 2.8) −1.53 (−1.5;−1.6) 1.85 (1.8; 1.9) −0.41 (−0.4;−0.5) −1.36 (−1.3;−1.4) −1.56 (−1.5;−1.6) 1.14 (1.1; 1.2) 5.03 (5; 5.1)

−2.03 (−5.3; 1.8) 1.46 (−1.0; 2.9) −1.52 (−4.1; 1.4) −5.27 (−5.5;−4.7) 3.03 (−1.4; 10.4) −0.98 (−2;−0.4) −1.23 (−2.5; 1.4) 2.07 (1.2; 3.6) −0.83 (−3.7; 0.5) −0.17 (−2.6; 3.5) 0.43 (−1; 2) −2.33 (−4; 0.1) −2.02 (−4.4;−0.2) −1.53 (−3.8;−0.4) 1.59 (0.1; 2.2)

0.462 0.609 0.421 0.588 0.514 0.290 0.388 0.880 0.914 0.317 0.878 0.991 0.740 0.736 0.443

Fast

Normal

10◦ incline

5◦ incline

Decline

To assess the influence of altering the hip anatomy on the gait performances, we classified the peri-prosthetic soft-tissue balance into 6 different groups (Fig. 2), by combining the RatioGHO and RatioGVO . Group B: moderate soft-tissue loosening. GVO or GHO ratios restored while the other ratio had changes less than 15%; Group C: normal softtissue tension. GHO and GVO ratios restored; Group D: slight soft-tissue tension change. GHO ratio had increased >15% and GVO ratio decreased <−15% or GVO ratio had increased >15% and GHO ratio decreased <−15%; Group E: moderate soft-tissue stretching. GHO ratio restored while GVO increased >15% or GVO ratio restored while GHO increased >15%; Groups A and F are not illustrated because they did not include any subject. All the variables were presented as medians (lower quartile, upper quartile).

of the superior femoral neck cortico-cancellous junction. In contrast, the FO generated with THR is mainly dictated by the residual joint laxity during the piston test, with the capacity for surgeons to reduce this laxity by artificially increasing the FO via selection of high offset stem design and/or high neck length (L, XL) modular head options. As surgeons generally fear prosthetic instability with THR, they tend to reduce the residual laxity by voluntarily tensioning the peri-prosthetic soft-tissue. Overall, we found that HR generated a more physiological gait than THR, mainly under speed conditions. Nevertheless, none of the differences in gait performance between the two procedures reached statistical significance. Few studies report on comparison of gait performances between HR and THR patients. Peterson et al. [28] and Lavigne et al. [29] did not find significant gait

performance differences between HR patients and individuals having been implanted with 28 mm head THA [28] and large diameter head THR [29]. While the former authors [28] compared gait performances under normal conditions (˜4.4 km/h walking speed), the latter [29] investigated normal and stress (fast 6.5 km/h walking speed) conditions. In contrast, others studies found that HR restored a more physiological gait pattern under higher speed conditions, when compared to THR [30,31]. Gerhardt et al. [30] found HR patients reached a higher walking speed, and preserved a more physiological weight acceptance and range of hip flexion compared to THR patients. Aquil et al. [31] also showed that increasing walking speed correlated strongly with differences in weight acceptance (r = 0.9) and push off force (r = 0.79) between the two limbs. The more symmetrical gait achieved with HR highlights the

532

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

Table 6 This table illustrates the relationship between radiographic frontal hip parameters and gait performances when walking at normal speed on a flat plane.

THR Ratio vertical centre of rotation (VCOR) Ratio horizontal COR (HCOR) Ratio femoral offset (FO) Ratio limb-length (LL) Ratio global horizontal offset (GHO) HR Ratio global vertical offset (GVO) Ratio vertical centre of rotation (VCOR) Ratio horizontal COR (HCOR) Ratio femoral offset (FO) Ratio limb-length (LL) Ratio global horizontal offset (GHO) Ratio global vertical offset (GVO)

SI weight acceptance peak force

SI weight acceptance peak time

SI Mid support force

SI Mid support time

SI Push off peak force

SI Push off peak time

r = 0.129 p = 0.429 r = 0.158 p = 0.332 r = 0.194 p = 0.231 r = −0.003 p = 0.984 r = 0.336 p = 0.034 r = 0.033 p = 0.839 r = 0.245 p = 0.442 r = −0.179 p = 0.579 r = 0.541 p = 0.069 r = −0.432 p = 0.161 r = 0.401 p = 0.196 r = −0.422 p = 0.172

r = 0.100 p = 0.538 r = −0.108 p = 0.505 r = 0.104 p = 0.524 r = 0.005 p = 0.974 r = 0.030 p = 0.853 r = −0.093 p = 0.570 r = −0.039 p = 0.904 r = 0.096 p = 0.766 r = −0.644 p = 0.024a r = 0.213 p = 0.507 r = −0.529 p = 0.077 r = 0.237 p = 0.458

r = −0.144 p = 0.376 r = −0.137 p = 0.399 r = −0.145 p = 0.371 r = 0.034 p = 0.835 r = −0.275 p = 0.086 r = 0.005 p = 0.977 r = −0.062 p = 0.847 r = 0.431 p = 0.162 r = −0.476 p = 0.117 r = 0.307 p = 0.332 r = −0.231 p = 0.70 r = 0.402 p = 0.195

r = 0.075 p = 0.646 r = −0.052 p = 0.748 r = 0.030 p = 0.854 r = 0.107 p = 0.513 r = −0.011 p = 0.949 r = −0.014 p = 0.933 r = 0.361 p = 0.249 r = 0.193 p = 0.548 r = −0.461 p = 0.131 r = 0.047 p = 0.884 r = −0.271 p = 0.395 r = 0.362 p = 0.247

r = 0.075 p = 0.644 r = 0.089 p = 0.586 r = 0.122 p = 0.491 r = −0.135 p = 0.406 r = 0.199 p = 0.217 r = −0.057 p = 0.725 r = 0.171 p = 0.595 r = −0.333 p = 0.289 r = 0.028 p = 0.932 r = −0.115 p = 0.722 r = −0.107 p = 0.742 r = −0076 p = 0.813

r = −0.36 p = 0.824 r = 0.098 p = 0.547 r = −0.055 p = 0.736 r = 0.106 p = 0.515 r = 0.004 p = 0.980 r = 0.128 p = 0.430 r = 0.470 p = 0.123 r = −0.188 p = 0.558 r = −0.373 p = 0.233 r = −0.16 p = 0.962 r = −0.351 p = 0.263 r = 0.399 p = 0.199

SI: Gait Symmetry Index; THR: total hip replacement; HR: hip resurfacing. a Statistical significance (p = 0.03).

importance of preserving the femoral neck (bone proprioceptors and physiological soft-tissue tension) and native head size, which seems to prevent generation of aberrant prosthetic hip biomechanics [13,32,33]. We were unable to detect significant gait performance differences between THR patients with various estimated quality of anatomical reconstruction and soft-tissue tension (Table 5). The radiographic estimation of the quality of the frontal anatomical hip restoration therefore seems to be of poor value in predicting the gait performance of THR patients. The study limitations mentioned below probably explain our findings. It is probable that restoring both axial (neck anteversion/anterior offset) and frontal (length and FO) native anatomical femoral neck parameters when performing THR is of importance in order to generate physiological peri-articular soft-tissue tension, hip kinematics, and gait performance. The fact that the conventional technique for THR (systematic non physiological implantation) does not primarily aim to restore the constitutional hip axial anatomy may explain why solely restoring the frontal hip anatomy when conventionally implanting THR components is not sufficient to generate significant gait benefit. This also probably explains the functional superiority of HR over THR, and further supports the relevance of performing anatomic or kinematic implantation of THR components (kinematic alignment technique for THR) [11,12]. In contrast with our study, a few papers found a relationship:

• reduction of physiological femoral offset compromising abductor function has been reported: Sariali et al. [25] found that a decrease in FO affected gait symmetry (reduced ROM and lower maximal swing speed) between operated and healthy limbs; Asayama et al. [26] found a decrease of 15% in FO generates weakness of the abductor muscle, while a larger femoral offset decreases the hip abductor muscle force required to walk; • the functional effect of post-THR limb-length discrepancy (LLD) remains less clear: Rösler et al. [34] found no significant disturbance of gait kinematics in the case of asymptomatic

infra-centimetric LLD in 26 patients; Li et al. [35] compared patients with symptomatic (15 patients, average LLD 20 mm – 11.9 to 28.1 mm) or asymptomatic LLD (15 patients, average LLD 10.3 mm – 4.7 to 15.9 mm) and found that symptomatic patients had decreased gait velocity by 0.2 m/s, decreased stride length by 0.3 m, and a 34% higher mid-stance ground reaction force; • the effect on gait performance of the restoration of COR has scarcely been studied: Rösler et al. [34] found that only a proximal location of the prosthetic COR affected gait parameters; Tsai et al. [36] found that COR medialisation and leg lengthening increased the internal rotation of the implanted hip when walking; • finally, the head diameter seems to have a negligible impact on gait performances [37].

It is important to acknowledge a few limitations of our methods that may affect the generalization of our results. Firstly, our findings are likely to be affected by cofounding bias due to the absence of randomisation, matching, and adjustment processes. However, this study could be considered as a basis for future randomized studies by providing basic data to calculate power and sample. Secondly, our study had an insufficient number of HR patients, resulting in statistical tests often being underpowered with the potential subsequent generation of statistical errors type 2. To overcome this limitation, we only used non parametrical tests. Thirdly, radiographic measurements of the FO are known to be inaccurate when compared to 3D measurements, and poorly estimate the true FO [38,39]. This limitation renders difficult the estimation of both the hip anatomical restoration and the peri-articular soft-tissue tension from radiographic pelvis X-rays, and therefore attenuates the relevance of our results for question 3. Despite this limitation, the data provided in the current study were clinically relevant considering that the large majority (72%) of FO measurements on plain X-rays had an error less than 5 mm versus CT-scan [40]. Fourthly, we only estimated the prosthetic anatomical reconstruction in the frontal plane on pelvic radiograph, neglecting the axial plane. However, alteration of the native individual femoral neck anteversion

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

(axial plane) when performing conventional THR would probably negatively influence peri-prosthetic soft-tissue balance, hip kinematics, and ultimately the gait performance. Further investigations are needed to assess the influence of axial hip anatomy restoration on THR function. Finally, we took the contra-lateral healthy hip anatomy as a reference to determine the quality of the prosthetic anatomical reconstruction, despite the fact that hips are often not completely symmetric. However, severe hip asymmetry is unlikely in our study population as our patients undertook hip replacement to cure a primary osteoarthritis, and they were known to have no other comorbidities affecting their gait performance [41]. 5. Conclusions The HR procedure is more consistent than conventional THR in generating a more physiological gait under stress conditions. Radiographic estimation of the quality of the frontal anatomical hip restoration is of poor value to predict gait performances of THR patients. Disclosure of interest Outside the current study Charles Rivière declares being a paidconsultant for Medacta, and Justin Cobb declares being a consultant for Biomet-Zimmer, Mathortho, to receive fees from Microport, , and to be involved in the development of a ceramic hip resurfacing. The other authors declare that they have no competing interest. Funding The institution received funding from Depuy for this project. Contribution Cedric Maillot: the conception and design of the study, or acquisition of data, or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content, final approval of the version to be submitted and statistics. Edouard Auvinet: the conception and design of the study, or acquisition of data, or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content, final approval of the version to be submitted and statistics. Ciara Harman: drafting the article or revising it critically for important intellectual content and final approval of the version to be submitted. Charles Rivière: the conception and design of the study, or acquisition of data, or analysis and interpretation of data, drafting the article or revising it critically for important intellectual content and final approval of the version to be submitted. Justin Cobb performed the prosthetic implantations, was involved in conception and design of the study, and revising the manuscript critically for important intellectual content and final approval of the version to be submitted. References [1] Naal FD, Impellizzeri FM, Lenze U, Wellauer V, von Eisenhart-Rothe R, Leunig M. Clinical improvement and satisfaction after total joint replacement: a prospective 12-month evaluation on the patients’ perspective. Qual Life Res 2015;24:2917–25. [2] Peters RM, van Beers LW, van Steenbergen LN, Wolkenfelt J, Ettema HB, et al. Similar superior patient-reported outcome measures for anterior and posterolateral approaches after total hip arthroplasty: postoperative patient-reported outcome measure improvement after 3 months in 12,774 primary total hip arthroplasties using the anterior, anterolateral, straight lateral, or posterolateral approach. J Arthroplasty 2018;33:1786–93.

533

[3] Girard J, Lons A, Ramdane N, Putman S. Hip resurfacing before 50 years of age: a prospective study of 979 hips with a mean follow-up of 5.1 years. Orthop Traumatol Surg Res 2018;104:295–9. [4] Girard J, Lons A, Pommepuy T, Isida R, Benad K, Putman S. High-impact sport after hip resurfacing: the ironman triathlon. Orthop Traumatol Surg Res 2017;103:675–8. [5] Sariali E, Klouche S, Mamoudy P. Investigation into three dimensional hip anatomy in anterior dislocation after THA. Influence of the position of the hip rotation centre. Clin Biomech 2012;27:562–7. [6] Baghdadi YMK, Larson AN, Sierra RJ. Restoration of the hip center during THA performed for protrusio acetabuli is associated with better implant survival. Clin Orthop Relat Res 2013;471:3251–9. [7] Sakalkale DP, Sharkey PF, Eng K, Hozack WJ, Rothman RH. Effect of femoral component offset on polyethylene wear in total hip arthroplasty. Clin Orthop Relat Res 2001;388:125–34. [8] Kleemann RU, Heller MO, Stoeckle U, Taylor WR, Duda GN. THA loading arising from increased femoral anteversion and offset may lead to critical cement stresses. J Orthop Res 2003;21:767–74. [9] Hayashi S, Nishiyama T, Fujishiro T, Hashimoto S, Kanzaki N, Nishida K, et al. Excessive femoral offset does not affect the range of motion after total hip arthroplasty. Int Orthop 2013;37:1233–7. [10] Windhagen H, Chincisan A, Choi HF, Thorey F. Soft-tissue balance in short and straight stem total hip arthroplasty. Orthopedics 2015;38:14–20. [11] Rivière C, Harman C, Parsons T, Villet L, Cobb J, Maillot C. Kinematic alignment versus conventional techniques for total hip arthroplasty: a retrospective case control study. Orthop Traumatol Surg Res 2019;105:895–905. [12] Rivière C, Maillot C, Harman C, Cobb J. Kinematic alignment technique for total hip arthroplasty. Sem Art 2018;29:330–43. [13] Girard J, Lavigne M, Vendittoli PA, Roy AG. Biomechanical reconstruction of the hip: a randomised study comparing total hip resurfacing and total hip arthroplasty. J Bone Joint Surg Br 2006;88:721–6. [14] Herman KA, Highcock AJ, Moorehead JD, Scott SJ. A comparison of leg length and femoral offset discrepancies in hip resurfacing, large head metal-on-metal and conventional total hip replacement: a case series. J Orthop Surg 2011;6:65. [15] Arnould A, Boureau F, Benad K, Pasquier G, Migaud H, Girard J. Computed tomography evaluation of hip geometry restoration after total hip resurfacing. Orthop Traumatol Surg Res 2015;101:571–5. [16] Huo SC, Wang F, Dong -J, Wei W, Zeng JQ, Huang HX, et al. Short-stem prostheses in primary total hip arthroplasty: a meta-analysis of randomized controlled trials. Medicine (Baltimore) 2016;95:e5215. [17] Liang HD, Yang WY, Pan JK, Huang HT, Luo MH, Zeng LF, et al. Are shortstem prostheses superior to conventional stem prostheses in primary total hip arthroplasty? A systematic review and meta-analysis of randomised controlled trials. BMJ Open 2018;8:e021649. [18] Ortiz-Declet VR, Iacobelli DA, Yuen LC, Perets I, Chen AW, Domb BG. Birmingham hip resurfacing vs total hip arthroplasty: a matched-pair comparison of clinical outcomes. J Arthroplasty 2017;32:3647–51. [19] Hamilton DF, Loth FL, Giesinger JM, Giesinger K, MacDonald DJ, Patton JT, et al. Validation of the English language Forgotten Joint Score-12 as an outcome measure for total hip and knee arthroplasty in a British population. Bone Joint J 2017;99:218–24. [20] Herzog W, Nigg BM, Read LJ, Olsson E. Asymmetries in ground reaction force patterns in normal human gait. Med Sci Sports Exerc 1989;21:110–4. [21] Tanaka R, Shigematsu M, Motooka T, Mawatari M, Hotokebuchi T. Factors influencing the improvement of gait ability after total hip arthroplasty. J Arthroplasty 2010;25:982–5. [22] Ewen AM, Stewart S, St Clair Gibson A, Kashyap SN, Caplan N. Post-operative gait analysis in total hip replacement patients – A review of current literature and meta-analysis. Gait Posture 2012;36:1–6. [23] Aqil A, Wiik A, Zanotto M, Manning V, Masjedi M, Cobb JP. The effect of hip arthroplasty on osteoarthritic gait: a blinded, prospective and controlled gait study at fast walking Speeds. J Arthroplasty 2016;31:2337–41. [24] Oberg T, Karsznia A, Oberg K. Basic gait parameters: reference data for normal subjects, 10–79 years of age. J Rehabil Res Dev 1993;30:210. [25] Sariali E, Klouche S, Mouttet A, Pascal-Moussellard H. The effect of femoral offset modification on gait after total hip arthroplasty. Acta Orthop 2014;85:123–7. [26] Asayama I, Chamnongkich S, Simpson KJ, Kinsey TL, Mahoney OM. Reconstructed hip joint position and abductor muscle strength after total hip arthroplasty. J Arthroplasty 2005;20:414–20. [27] Silva M, Lee KH, Heisel C, Dela Rosa MA, Schmalzried TP. The biomechanical results of total hip resurfacing arthroplasty. J Bone Joint Surg Am 2004;86:40–6. [28] Petersen MK, Andersen NT, Mogensen P, Voight M, Søballe K. Gait analysis after total hip replacement with hip resurfacing implant or mallory-head exeter prosthesis: a randomised controlled trial. Int Orth 2011;35:667–74. [29] Lavigne M, Therrien M, Nantel J, Roy A, Prince F, Vendittoli PA. The functional outcome of hip resurfacing and large-head THA is the same: a randomized, double-blind study. Clin Orthop Relat Res 2010;468:326–36. [30] Gerhardt DM, Mors TG, Hannink G, Van Susante JL. Resurfacing hip arthroplasty better preserves a normal gait pattern at increasing walking speeds compared to total hip arthroplasty. Acta Orthop 2019;28:1–9. [31] Aqil A, Drabu R, Bergmann JH, Masjedi M, Manning V, Andrews B, et al. The gait of patients with one resurfacing and one replacement hip: a single blinded controlled study. Int Orthop 2013;37:795–801.

534

C. Maillot et al. / Orthopaedics & Traumatology: Surgery & Research 106 (2020) 527–534

[32] Nantel J, Termoz N, Vendittoli PA, Lavigne M, Prince F. Gait patterns after total hip arthroplasty and surface replacement arthroplasty. Arch Phys Med Rehabil 2009;90:463–9. [33] Szymanski C, Thouvarecq R, Dujardin F, Migaud H, Maynou C, Girard J. Functional performance after hip resurfacing or total hip replacement: a comparative assessment with non-operated subjects. Orthop Traumatol Surg Res 2012;98:1–7. [34] Rösler J, Perka C. The effect of anatomical positional relationships on kinetic parameters after total hip replacement. Int Orthop 2000;24:23–7. [35] Li J, McWilliams AB, Jin Z, Fisher J, Stone MH, Redmond AC, et al. Unilateral total hip replacement patients with symptomatic leg length inequality have abnormal hip biomechanics during walking. Clin Biomech 2015;30:513–9. [36] Tsai TY, Li JS, Dimitriou D, Kwon YM. Does component alignment affect gait symmetry in unilateral total hip arthroplasty patients? Clin Biomech 2015;30:802–7.

[37] Zagra L, Anasetti F, Bianchi L, Licari V, Giacometti Ceroni R. No Difference in gait recovery after THA with different head diameters: a prospective randomized study. Clin Orthop Relat Res 2013;471:3830–7. [38] Lazennec JY, Chometon Q, Folinais D, Robbins CB, Pour AE. Are advanced threedimensional imaging studies always needed to measure the coronal knee alignment of the lower extremity? Int Orthop 2017;41:917–24. [39] Lazennec JY, Brusson A, Dominique F, Rousseau MA, Pour AE. Offset and anteversion reconstruction after cemented and uncemented total hip arthroplasty: an evaluation with the low-dose EOS system comparing two- and threedimensional imaging. Int Orthop 2015;39:1259–67. [40] Lecerf G, Fessy MH, Philippot R, Massin P, Giraud F, et al. Femoral offset: anatomical concept, definition, assessment, implications for preoperative templating and hip arthroplasty. Orthop Traumatol Surg Res 2009;95:210–9. [41] Young EY, Gebhart J, Cooperman D, Ahn NU. Are the left and right proximal femurs symmetric? Clin Orthop Relat Res 2013;471:1593–601.