HIP CAPSULE PRESERVATION FOLLOWING ANTERIOR APPROACH TOTAL HIP ARTHROPLASTY: THE EFFECT ON GAIT BIOMECHANICS

Preservation and repair of the hip capsule following total hip arthroplasty (THA) is recommended when performing a posterior surgical approach, due to increased dislocation risk when left unrepaired (1). However, there is less consensus regarding capsule preservation when performing an anterior approach. Any improvements in stability/function afforded by an intact capsule may be evident when analyzing patients’ gait biomechanics. The objective of this research was to therefore investigate whether preserving the hip joint capsule during an anterior approach THA has an effect on the post-operative kinematics and kinetics of gait. Two groups of patients who underwent an anterior approach THA were studied. Ten patients underwent a capsulotomy, where the hip capsule was repaired at the end of the procedure (6 F, 4 M, age 67.0 ± 4.9yrs) (capsulotomy group), while another 10 patients underwent a partial capsulectomy, where a portion of the capsule is excised (5 F, 5 M, age 65.6 ± 3.1yrs) (capsulectomy group). A further 10 healthy control participants (5 F, 5 M, age 65.3 ± 4.0yrs) (control group) were also included in the study. Three-dimensional gait biomechanics were assessed 12 months following surgery using motion capture and force plate analysis. Statistical parametric mapping (SPM) was used to detect the presence and timing of significant differences in hip kinematics and kinetics during the gait cycle. Spatiotemporal gait parameters were also calculated using the motion capture heel markers and normalized to leg length. To account for additional factors that may influence biomechanical outcomes, hip offset was measured post-operatively via radiographic assessment on both the operated and un-operated side. During early stance phase (3%-28% of the gait cycle), the capsulectomy group showed significantly lower external adduction moments in comparison to the control group, but no significant differences were detected compared to the capsulotomy group. The patient groups exhibited significant differences in their operated/unoperated hip offset, although both group averages remained within ranges deemed to be clinically meaningful (capsulotomy = -2.3 ± 2.5mm, capsulectomy = 2.8 ± 5.1mm)(2). Spatiotemporal gait parameters as well as sagittal and frontal plane hip kinematics between the groups showed no significant differences. Ensuring proper stability in the frontal plane of the hip is crucial for a healthy walking pattern. After total hip arthroplasty (THA), it is commonly observed that patients undergo a decrease in external adduction moments in the hip that has undergone surgery (3). Nevertheless, our findings suggest that retaining the hip capsule during the surgical procedure could enhance the stabilization of the hip joint during the initial stance phase of walking, promoting a more typical distribution of load in the frontal plane. Further investigation is warranted given the limited number of participants and the lack of direct distinctions between the groups of patients.