Does surgical approach or prosthesis type affect hip joint loading one year after surgery?

Gait & Posture 44 (2016) 74–82

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Does surgical approach or prosthesis type affect hip joint loading one year after surgery? Mariska Wesseling a,*, Christophe Meyer b, Kristoff Corten c, Jean-Pierre Simon d, Kaat Desloovere b,e, Ilse Jonkers a a

KU Leuven, Department of Kinesiology, Human Movement Biomechanics, Heverlee, Belgium KU Leuven, Department of Rehabilitation Sciences, Leuven, Belgium Hip Unit, Orthopaedic Department, Ziekenhuis Oost-limburg, Genk, Belgium d UZ Pellenberg Orthopedic Department, University Hospitals Leuven, Pellenberg, Belgium e Clinical Motion Analysis Laboratory, University Hospitals Leuven, Pellenberg, Belgium b c

A R T I C L E I N F O

A B S T R A C T

Article history: Received 4 May 2015 Received in revised form 21 October 2015 Accepted 15 November 2015

Several approaches may be used for hip replacement surgery either in combination with conventional total hip arthroplasty (THA) or resurfacing hip arthroplasty (RHA). This study investigates the differences in hip loading during gait one year or more after surgery in three cohorts presenting different surgical procedures, more specific RHA placed using the direct lateral (RHA-DLA, n = 8) and posterolateral (RHAPLA, n = 14) approach as well as THA placed using the direct anterior (THA-DAA, n = 12) approach. For the DAA and control subjects, hip loading was also evaluated during stair ascent and descent to evaluate whether these motions can better discriminate between patients and controls compared to gait. Musculoskeletal modelling in OpenSim was used to calculate in vivo joint loading. Results showed that for all operated patients, regardless the surgical procedure, hip loading was decreased compared to control subjects, while no differences were found between patient groups. This indicates that THA via DAA results in similar hip loading as a RHA via DLA or PLA. Stair climbing did not result in more distinct differences in hip contact force magnitude between patients and controls, although differences in orientation were more distinct. However, patients after hip surgery did adjust their motion pattern to decrease the magnitude of loading on the hip joint compared to control subjects. ß 2015 Elsevier B.V. All rights reserved.

Keywords: Hip arthroplasty Gait Stair ascent Stair descent Hip loading

1. Introduction Total hip arthroplasty (THA) is an often used procedure to treat end stage hip osteoarthritis. However, THA patients present altered gait kinematics compared to control subjects. Several studies have shown that gait kinematics of THA patients do not return to normal [1–3] and that, although improvements are found compared to the pre-operative condition, gait kinematics remain aberrant up to 10 years after surgery [4]. As an alternative to THA, resurfacing hip arthroplasty (RHA) is also performed, specifically for young patients given a better preservation of the tissue and reduced dislocation risk and shorter recovery time [5,6]. Previous studies have shown that kinematics and kinetics of patients after RHA are more comparable to control subjects [7,8]. However,

* Corresponding author at: KU Leuven, Human Movement Biomechanics Research Group, Tervuursevest 101 – box 1501, 3001 Leuven, Belgium. Tel.: +32 16 376463; fax: +32 16 329197. E-mail address: [email protected] (M. Wesseling). http://dx.doi.org/10.1016/j.gaitpost.2015.11.009 0966-6362/ß 2015 Elsevier B.V. All rights reserved.

others found no differences between THA and RHA [9,10] while deviations from control subjects remain. Apart from prosthesis type, the surgical approach is a factor known to affect the outcome after hip arthroplasty surgery. The direct lateral (DLA) [11], posterolateral (PLA) [12] and direct anterior (DAA) [13] approaches are all often performed. Specifically the DAA is suggested to result in decreased muscle damage and is therefore also often considered in young and more active patients [14]. However, in clinical follow-up studies, no clear difference in dislocation incidence, abductor strength or hip kinematics was reported between any of the approaches [15,16]. The differences in early post-operative gait kinematics were not conclusive as some authors report no superior results following minimal invasive surgery (MIS) [16,17] and others report better gait kinematics after DAA [18]. However, no differences were found in late post-operative gait kinematics and kinetics for DAA compared to the lateral approach [1] or between different MIS approaches [19]. Most studies investigating kinematics in hip replacement patients focus on the analysis of gait [2,4,8,9,16], which is only a subset of the relevant motions performed in daily living. Shrader

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et al. already reported more pronounced differences in kinematics and kinetics between THA patients and control subjects during stair ascent and descent [7]. Lamontagne et al. found that kinematics and kinetics of DAA patients during stair climbing were closer to controls compared to DLA patients, although both patient groups remained abnormal [20]. This suggests that these more demanding tasks might result in more distinct differences between patients and controls. On the other hand, Queen et al. reported no clear differences in stair climbing kinematics and kinetics between RHA and THA patients more than 12 months after surgery, while differences between patients and controls remained [10]. Despite the changes in kinematics and kinetics are indicative of the remaining functional disability, they are not indicative of changes in hip joint loading. Joint loading is often related to inferior implant survival as increased loading, due to, e.g., high activity levels, can affect the stress and fixation around the implant [21–23]. To investigate hip joint loading, musculoskeletal models have been used in combination with 3D motion capture data as a non-invasive method to calculate joint contact forces in vivo. Changes in kinematics and kinetics have been related to changes in hip joint loading during gait in healthy subjects [24] as well as in patients before and after THA [25]. Also decreased hip contact forces in THA patients compared to controls were found for gait as well as for stair negotiation [26,27]. To the best of our knowledge, hip contact forces were not yet compared across interventions. This is relevant as surgical procedure i.e. the specific combination of type of prosthesis and surgical approach, might affect the outcome in terms of kinetics and therefore contact forces. Weber et al. already suggested that the decreased muscle damage of an anterior approach could result in better symmetry of both the magnitude and orientation of the hip contact forces compared to a lateral approach [28]. However, so far no study confirmed an effect of surgical approach and prosthesis type on the hip contact forces during functional activities. This study investigates the differences in hip joint loading during gait between different surgical procedures (RHA-DLA, RHA-PLA and THA-DAA) in patients at least one year or more after surgery. It is hypothesized, based on the intervention-specific soft tissue damage, that differences in hip contact forces can be found, presenting hip contact forces closer to control values in DAA patients. For DAA and control subjects, hip joint loading was also evaluated during stair ascent and descent to evaluate if these motions can better discriminate between patients and controls, compared to gait. 2. Methods 2.1. Experimental procedure Three different surgical procedures were evaluated; the direct anterior (THA-DAA, n = 23), direct lateral (RHA-DLA, n = 8) and

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posterolateral (RHA-PLA, n = 14) approaches, and were compared to a group of healthy control subjects (n = 18). For all patients inclusion criteria were: a BMI < 35 kg/m2, unilateral hip osteoarthritis associated with hip pain, no other orthopaedic comorbidities such as lower limb osteoarthritis, joint replacement or neuromuscular disease, neurological complications and lowback pain that could affect gait. Similar inclusion criteria were applied for the recruitment of the control subjects with the exception of painful and/or diagnosed hip OA. Subjects were only recruited based on verbal screening to examine the absence of pain and/or diagnosed OA. Patients operated via the DAA received a conventional total hip arthroplasty (THA), while the other patients received a resurfacing hip arthroplasty (RHA). The PLA patients received a Birmingham hip resurfacing (Smith & Nephew), while DLA patients received a Durom hip resurfacing (Zimmer). All patients had a femoral head size larger than 36 mm. The study was approved by the local ethics committee and all subjects signed informed consent. Subject characteristics are reported in Table 1. All subjects performed three gait trials at self-selected speed. Control subjects and DAA patients also performed three stair ascent and three stair descent trials at self-selected speed. The Plug-in-Gait marker set of the lower limb and trunk (Vicon, Oxford Metrics, Oxford, UK) extended by a three-marker cluster on both upper and lower legs was used, which resulted in a total of 36 markers. Three-dimensional marker trajectories were captured using a Vicon system (100 Hz, VICON, Oxford Metrics, Oxford, UK) and ground reaction force data was measured using two AMTI force platforms (1500 Hz, Advanced Mechanical Technology Inc., Watertown, MA). 2.2. Musculoskeletal modelling A musculoskeletal model consisting of 14 segments, 19 degrees of freedom and 88 musculotendon actuators [29] including wrapping surfaces around the hip, was used. All simulations were done using the standard simulation workflow in OpenSim 3.1 [30]. The model was scaled based on the marker positions in a static pose. The pelvis was scaled non-uniformly based on the position of the markers on the anterior superior iliac spine (ASIS) and posterior superior iliac spine (PSIS), representing pelvis width (left to right ASIS) and depth (ASIS to PSIS). As the experimental markers were used, differences in pelvis dimensions were taken into account when scaling the model. An inverse kinematics procedure was used to calculate joint angles using 3D marker trajectories. An inverse dynamics procedure was used to calculate joint moments. Next, a static optimization procedure was used to calculate muscle forces using a minimization of the total squared muscle activations and taking into account the muscles force– length–velocity relationship. Finally hip contact forces were calculated. Hip moments and contact forces were normalized to body weight.

Table 1 Mean (standard deviation) for the subject characteristics. Significant differences (p < 0.05) with DAA are indicated with * and significant differences (p < 0.05) with controls are indicated with **.

No subjects Gender Age at time gait analysis (years) Height (m) BMI (kg/m2) Follow-up after surgery (months) Gait velocity (m/s) Stair ascent velocity (m/s) Stair descent velocity (m/s)

Controls

THA-DAA

RHA-DLA

RHA-PLA

18 9 females/9 males 53.00 (4.97) 1.71 (0.10) 23.67 (3.14) – 1.34 (0.20) 0.73 (0.13) 1.13 (0.23)

12 6 females/6 males 47.75 (13.16) 1.69 (0.87) 25.52 (3.02) 13.67 (1.83) 1.25 (0.13) 0.67 (0.08) 1.01 (0.22)

8 2 females/6 males 55.25 (8.45) 1.72 (0.79) 26.17 (3.87) 34.75 (13.09)* 1.16 (0.13) – –

14 2 females/12 males 52.29 (11.78) 1.73 (0.69) 25.31 (2.56) 52.64 (23.66)* 1.14 (0.15)** – –

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2.3. Data analysis Internal joint moments in hip flexion, abduction and rotation as well as resultant hip contact forces and orientation were calculated. A Kruskal–Wallis test was used to test for significant differences in these variables at the time instances of the first and second peaks (at initial and terminal double support respectively) in hip contact force. Significant differences were confirmed for p < 0.05. In case of a significant difference, a post hoc multiple comparison test using a Bonferroni correction was used to determine between which groups differences were found. Also subject characteristics were tested for significant differences using a Kruskal–Wallis test (significant difference when p < 0.05) and a multiple comparison test with a Bonferroni correction in case of any significant differences. 3. Results The subject characteristics showed no differences in age, height or BMI between any of the groups (Table 1). The time of the followup after surgery was significantly longer for both the DLA and PLA patients compared to the DAA patients. For the PLA patients the gait speed was significantly slower compared to the control subjects. During gait, internal hip moments as well as hip contact forces were decreased for all patient groups (Fig. 1). At the first peak in hip contact forces, only DLA patients showed significantly decreased

contact forces compared to controls (average of 2.84 BW and 3.39 BW, respectively; Fig. 2A). Hip abduction moments were decreased compared to controls, specifically for DLA and PLA patients (average of 0.77 Nm/kg for controls and 0.56 Nm/kg for DLA, 0.63 Nm/kg for PLA; Fig. 4A). At the second peak in hip contact forces, all patients showed decreased contact forces (average of 5.21 BW for controls and 4.39 BW for DAA, 4.29 BW for DLA, 4.21 BW for PLA; Fig. 2A). At the second peak all joint moments were decreased, although significant differences varied between procedures (Fig. 4A). While the hip flexion moment was significantly decreased in DLA patients, a significant decrease was found for the hip abduction moment in DAA patients and for the hip rotation moment in PLA patients, compared to controls. No significant differences in orientation were found between any of the groups at the time instances of either the first or second peak in contact force during gait (Fig. 3A). For stair ascent, hip contact forces were decreased for DAA patients compared to controls (Fig. 1). The magnitude of the hip contact forces was significantly different at the first peak (average of 3.74 BW and 3.21 BW for controls and DAA patients respectively; Fig. 2B). Also the orientation in the frontal and sagittal planes was decreased at this time instant (Fig. 3B), indicating hip contact forces for DAA patients were orientated more vertical compared to controls. The hip abduction moment was decreased in patients at the first peak (average of 0.64 Nm/kg in controls and 0.52 Nm/ kg in DAA patients; Fig. 4B), while during gait no significant differences were found for DAA patients. At the second peak no

Fig. 1. Average hip flexion (A), abduction (B) and rotation (C) moments as well as hip contact forces (D) for gait (left), stair ascent (middle) and stair descent (right) for all subject groups. The grey area represents the standard deviation for control subjects.

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Fig. 2. First and second peak hip contact force in gait (A), stair ascent (B) and stair descent (C) for the different subject groups. Significantly different groups are indicated with an asterisk (*).

significant differences were found for either magnitude (Fig. 4C) or orientation (Fig. 3B) of the hip contact force or the hip moments. For stair descent, hip contact forces were slightly decreased for DAA patients (Fig. 1), however, no significant differences were found in magnitude (Fig. 2C). The orientation in the transversal plane at the time instant of the second peak in contact force was significantly different, where orientation was more anterior for DAA patients (Fig. 3C). In the hip abduction moment a slight but significant decrease was found for DAA patients at the time of the first peak in contact force (average of 0.97 Nm/kg for controls and 0.87 Nm/kg for DAA patients; Fig. 4B). 4. Discussion The goal of this study was to investigate the differences in hip joint loading between different surgical procedures (THA-DAA, RHA-DLA and RHA-PLA) in patients one year or more after surgery. Although loading on the hip joint was decreased in patients compared to controls, no differences were found between patient groups treated with different surgical procedures at the current evaluation point. This finding contrasts the suggestions in previous research that the decreased muscle damage of an anterior approach results in more symmetrical hip loading compared to other approaches [28]. Gait kinematics more comparable to control subjects have been reported after RHA compared to THA [7,8]. As no differences between patient groups were found in the present study, this indicates that a THA using the DAA results in similar hip loading as a RHA via the DLA or PLA. The fact that the RHA-DLA and RHA-PLA patients were evaluated longer after surgery than the

THA-DAA patients, even adds to this conclusion. Nevertheless, all patients were minimally 12 months after surgery, at which a full functional recovery is to be expected [19]. Although hip joint loading was not significantly different between patient groups treated with different surgical procedures, all patients did show aberrant hip contact forces compared to healthy controls. In gait, differences in hip contact forces between patients and controls were specifically found at terminal double support, i.e. the second peak in contact force. All patient groups showed decreased contact forces at this time instant. In accordance with previous research [1–3,26] none of the patient groups returned to normal even more than one year after surgery. For the RHA-DLA patients also decreased contact forces at initial double support were found compared to control subjects. This might be related to the decreased walking velocity that was found in these patients, since contact forces decrease with decreasing walking velocity [26]. However, the effect of gait velocity was only limited for our subjects (supplementary material A). Despite the differences in hip contact force magnitude between patients and controls during gait, the orientation was similar. These findings confirm previous research that already indicated a normalization of the load orientation six weeks after surgery [25]. Limited differences between controls and THA-DAA patients were found during stair ascent and descent, which is in contrast to previous studies which suggested that these tasks can be used to find larger differences in kinematics and kinetics compared to gait [7,20]. Also differences in internal hip moments were limited. Interestingly, the magnitude of the hip contact force was not larger for stair ascent and descent than for gait. Specifically at the second

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Fig. 3. Orientation angles at the first and second peak hip contact force in gait (A), stair ascent (B) and stair descent (C) for the different subject groups. Significantly different groups are indicated with an asterisk (*).

Fig. 3. (Continued ).

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Fig. 3. (Continued ).

peak, hip contact forces appeared decreased for stair ascent (4.65 BW for controls and 3.95 BW for THA-DAA patients) and descent (4.28 BW for controls and 3.76 BW for THA-DAA patients) compared to gait (5.21 BW for controls and 4.38 BW for THA-DAA patients; Figs. 1 and 2). Hip contact forces during stair ascent were only significantly decreased at initial double support, which has been reported before [26,27]. Bergmann et al. reported only slightly increased hip loading using instrumented prostheses during stair ascent and descent compared to gait [31] and also Stansfield and Nicol reported similar or decreased loading [26]. This indicates that stair ascent and descent cannot be labelled as higher demanding tasks than gait in terms of hip joint loading magnitude. In contrast, hip loading orientation did discriminate between DAA patients and controls during stair ascent (presenting a more vertical loading in DAA patients) and descent (presenting a more anterior loading in DAA patients), while this was not found during gait. Therefore, stair climbing will induce altered loading conditions in the DAA patients, therefore affecting the loading of the prosthesis: the more vertical loading during stair ascent will induce a higher medial bending action on the femur and induce increased tensile stress on the lateral side of the femur but compressive stress on the medial side [22]. The more anterior loading in stair descent will increase the torsional loading in the femur. Future research is therefore needed to evaluate the effect of the decreased loading magnitude against the effect to the altered loading direction in order to better understand potential risks associated with stair climbing, as these insights may affect the staging of clinical rehabilitation protocols. A limitation of this study is that DAA patients received a THA, while patients operated via the DLA and PLA received a RHA. This design did not allow indicating whether surgical approaches or

prosthesis type (THA and RHA) could result in changes in hip loading. To be able to define the isolated effect of surgical approach and prosthesis type, a design involving six cohorts, i.e. THA-DAA, THA-DLA, THA-PLA and RHA-DAA, RHA-DLA, RHA-PLA, should be investigated. However, RHA via the DAA is a difficult surgery which is not often performed [32]. Besides that, a multi-centre study will be necessary as experienced surgeons for each approach need to be involved. Since stair ascent and descent were only available for DAA patients, it was not possible to investigate differences between the different patient groups using these tasks. Therefore it could not be determined if stair ascent and descent could distinguish better between the patient groups, as has been suggested before [20]. Besides that, several assumptions were made for the musculoskeletal modelling. We used similar maximal isometric muscle forces for both control subjects and patients. However, in hip arthroplasty patients, muscle parameters might have changed following the surgery or due to the OA process. As patients were one or more years after surgery it was assumed that soft tissue repair had proceeded to return to their original function, this approach seems valid. We also assumed the hip joint centre did not change, despite the placement of a prosthesis. An altered hip joint centre can affect muscle moment arms and therefore muscle and hip contact forces. Also, calculated hip contact forces were increased compared to previously reported contact forces measured using instrumented prostheses [31]. This has been reported before [33] and might partially be explained by differences in gait characteristics and more specific differences in patient-specific joint moments. In conclusion, results showed that patients after hip surgery adjusted their gait pattern to decrease the magnitude of loading on the hip joint. In gait, patients operated via the DAA with a THA

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Fig. 4. Internal hip moments at the time of the first and second peak in hip contact force during gait (A) and for the first (B) and second (C) peak in stair ascent and descent for the different subject groups. Significantly different groups are indicated with an asterisk (*).

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C Fig. 4. (Continued ).

showed similar hip contact forces as patients operated via the DLA and PLA who received a RHA. Although, stair climbing did not result in more pronounced differences in hip contact force magnitude between THA-DAA patients and controls, the pronounced effect on loading orientation is a strong indication for including stair climbing activities in protocols evaluating functional outcome after surgical intervention. Acknowledgment This work was funded by the Agency for Innovation by Science and Technology (IWT-TBM no. 100786). The funder had no role in the study. Conflict of interest The authors have no conflicts of interest to report.

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