Complete Capsular Repair Restores Native Kinematics After Interportal and T-Capsulotomy

Abstract

Background: Although the use of hip arthroscopy continues to increase, capsular management remains a controversial topic. Purpose: To investigate the biomechanical effect of capsulotomy and capsular repair techniques on hip joint kinematics in varying combinations of sagittal and coronal joint positions. Study Design: Controlled laboratory study. Methods: Eight fresh-frozen hemi-pelvises (78.3 ± 6.0 years of age; 4 left, 6 male) were dissected of all overlying soft tissue, with the exception of the hip joint capsule. The femur was potted and attached to a load cell, while the pelvis was secured to a custom-designed fixture allowing static alteration of the flexion-extension arc. Optotrak markers were rigidly attached to the femur and pelvis to track motion of the femoral head with respect to the acetabulum. After specimen preparation, 7 conditions were tested: (1) intact, (2) after portal placement (anterolateral and midanterior), (3) interportal capsulotomy (IPC) (35 mm in length), (4) IPC repair, (5) T-capsulotomy (IPC +15-mm longitudinal incision), (6) partial T-repair (repair of longitudinal incision with IPC left open), (7) full T-repair. All conditions were tested in 15° of extension (–15°), 0°, 30°, 60°, and 90° of flexion. Additionally, all flexion angles were tested in neutral, as well as in specimen-specific maximum abduction and adduction, resulting in 15 testing positions. Internal rotation (IR) and external rotation (ER) moments of 3 N·m were manually applied to the femur via the load cell at each position. Rotational range of motion and joint kinematics were recorded. Results: In the neutral coronal plane, T-capsulotomy significantly increased IR/ER rotational range of motion compared with intact state at −15° (55.96°± 6.11° vs 44.92°± 7.35°, P < .001), while IPC significantly increased rotation compared with the portal state at 0° (60.09°± 6.82° vs 51.68°± 10.35°, P = .004). No statistically significant increases were found in mediolateral joint translation after IPC or T-capsulotomy. Similarly, no statistically significant increases were noted in anteroposterior translation after IPC or T-capsulotomy. Complete capsular repair restored near native joint kinematics, with no significant differences in rotation or translation between any complete capsular repair groups and the intact state, regardless of joint position. Conclusion: Universally, across all conditions, complete capsular repair after interportal or T-capsulotomy restored rotational range of motion and joint translation to values observed in the native joint. Clinical Relevance: Where feasible, complete capsular closure should be performed, especially after T-capsulotomy. However, further clinical evaluation is required to determine whether adverse kinematic parameters of an unrepaired capsule are associated with reduced patient-reported outcomes.