Comparison of total hip arthroplasty surgical approaches by Statistical Parametric Mapping

Highlights

• The effect of hip arthroplasty surgical approach on gait mechanics is unsettled.

• We used Statistical Parametric Mapping to explore hip kinematics after arthroplasty.

• Lateral and posterior surgical approaches lead to similar hip kinematics.

• Results revealed changes over time in hip adduction during weight acceptance.

• Traditional analysis of gait parameters may miss/overstate hip kinematic features.

Abstract

Background

The most common surgical approaches in use for total hip arthroplasty are the lateral and posterior. When comparing these approaches in terms of gait biomechanics, studies usually rely on pre-defined discrete variables related to the events of gait cycle. However, this analysis may miss differences in other parts of the movement pattern that are not explored. We applied Statistical Parametric Mapping to compare hip kinematics between patients who underwent arthroplasty using either a lateral or posterior approach, contrasting these results with discrete variable analysis.

Methods

Twenty-two participants (11 lateral, 11 posterior; age between 50 and 80 years) underwent gait analysis before, 3 weeks and 12 weeks after hip arthroplasty. One-dimensional (e.g. time-varying) trajectories and zero-dimensional (e.g. peak extension) discrete variables were used to assess differences between groups in each plane of hip movement (sagittal, frontal, and transverse).

Findings

One-dimensional and zero-dimensional analyses found no significant differences between groups. Statistical Parametric Mapping revealed that both groups presented significant changes over time in hip adduction at 11–43% of the gait cycle. Zero-dimensional analysis seems to overstate sagittal plane changes over time since no such changes were found by Statistical Parametric Mapping.

Interpretation

Our results agreed with previous studies suggesting that surgical approach do not affect hip kinematics at the early post-operative stage after arthroplasty. However, Statistical Parametric Mapping revealed changes in frontal plane kinematics over time that were underestimated by the zero-dimensional variables. These findings suggest hip adduction impairment up to 12 weeks after arthroplasty.

Introduction

Total hip arthroplasty (THA) is a successful joint replacement procedure that provides significant pain alleviation and improvement in physical function (Hammett et al., 2018). THA is common, with >1 million procedures undertaken every year globally, and rates for primary and revision THA increasing (Pivec et al., 2012). While several surgical approaches have been described to access the hip joint during surgery, worldwide, the most common approaches in use are posterior and lateral (Chechik et al., 2013). The lateral approach involves surgical separation of gluteus medius and vastus lateralis (Petis et al., 2015). In contrast, the posterior approach involves blunt separation and retraction of gluteus maximus, and requires a tenotomy of the short external rotators and a posterior capsulotomy (Petis et al., 2015). Several studies have revealed that both approaches lead to similar functional and clinical outcomes (Berstock et al., 2015; Greidanus et al., 2013; Jelsma et al., 2016; Petis et al., 2015). However, objective studies investigating these approaches in terms of the gait and walking ability of patients are still rare.

Gait analysis is an objective method that has been used to evaluate the clinical performance of a THA and to assess the quality of gait (Pospischill, 2010). It allows investigators to highlight small discrepancies in the joint mechanics which are out of the normal range or signs of improvement in function of THA patients (Ewen et al., 2012). Few studies have compared the lateral and posterior approaches in terms of gait analysis (Madsen et al., 2004; Petis et al., 2017; Queen et al., 2014, 2013; Zeni et al., 2018). Overall, these studies agree in that postoperative gait changes are similar between surgical approaches. In this literature, postoperative gait comparisons usually rely on pre-defined discrete variables (e.g. peak flexion angle, peak extension angle) that are then contrasted between approaches or to matched healthy controls. However, recent investigations suggest that this analysis may have limitations, since differences in other parts of the movement pattern that were not explored may be missed (Pataky et al., 2016b, Pataky et al., 2015). Thus, to shed light over the true impact of surgical approach on gait biomechanics, it may be necessary to compare surgical approaches with methods of statistical analyses that explore the entire movement trajectory, such as Statistical Parametric Mapping (SPM).

SPM originated for assessment of neuroimaging (Friston et al., 1995), and has also been used to analyse kinematic and kinetic data (Pataky et al., 2013) during walking (Castro et al., 2015) and running (De Ridder et al., 2013). While the analysis of discrete variables (0D) is based on traditional 0D Gaussian randomness, SPM uses the one-dimensional (1D) continuous trajectories that changes in time or space. Random Field Theory is used to make probabilistic conclusions based on the random behaviour of that 1D observational unit (Pataky et al., 2013). Thus, SPM provides statistical hypothesis testing in a continuous manner, directly on the original (registered) curves, were their spatiotemporal biomechanical context is immediately apparent (Pataky, 2012).

THA causes alteration in normal gait mechanics, particularly in hip kinematics (Eitzen et al., 2012; Ewen et al., 2012). For instance, hip range of motion correlates strongly with postoperative functional outcomes (Davis et al., 2007), with sagittal plane hip kinematics being a key feature regarding post-operative rehabilitation programs aiming to improve gait patterns (Colgan et al., 2016). Therefore, it may be important to explore hip kinematic continuous trajectories in order to reveal possible differences between surgical approaches. The aim of this study was to use SPM to compare hip joint kinematics between patients who underwent THA using either a lateral or posterior approach. We were also interested in the longitudinal kinematic outcomes between surgical approaches. Specifically, our goals were: i) use SPM to compare hip kinematics of the entire gait cycle trajectory (1D) between lateral and posterior THA operated patients; ii) utilise commonly used discrete variables (0D) (e.g. peak flexion angle, peak extension angle and flexion/extension range of motion (RoM)) to compare hip kinematics between lateral and posterior THA operated patients; iii) utilise 1D and 0D variables to compare hip kinematics before, 3 weeks and 12 weeks after surgery within each surgical approach group. The comparison between 1D and 0D analysis approaches may help in determining if 0D variables miss/overstate certain hip kinematic features during the gait of THA patients. Given that previous studies suggest differences in hip rotation between approaches (Petis et al., 2017) and an increase in flexion/extension ROM after surgery (Colgan et al., 2016; Zeni et al., 2018), we hypothesised that SPM analysis will reveal transversal and/or sagittal plane differences between the lateral and posterior approaches.