Summary

This cadaveric, biomechanical study evaluated the impact of capsular injury and repair on hip joint kinematics, focusing on both rotation and joint translation.

Abstract

Background

While hip arthroscopy utilization continues to increase, capsular management remains a controversial topic.

Purpose

To investigate the biomechanical effect of different capsulotomies 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 hemipelvises (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.
Following specimen preparation, seven conditions were tested: i) intact; ii) after portal placement (anterolateral and mid-anterior); iii) interportal capsulotomy (IPC) [35 mm in length]; iv) IPC repair; v)T-capsulotomy [15 mm longitudinal incision]; vi) partial T-repair (vertical limb); vii) 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 maximum abduction and adduction, resulting in 15 testing positions. 3Nm internal and external rotation moments were manually applied to the femur via the load cell at each position. Rotational range of motion and joint kinematics were recorded.

Results

IPC and T-capsulotomies increased rotational ROM and mediolateral (ML) joint translation in several different joint configurations, most notably from 0-30° in neutral abduction/adduction. Complete capsular repair restored near native joint kinematics, with no significant differences between any complete capsular repair groups and the intact state, regardless of joint position. An unrepaired IPC resulted in increased rotational ROM, but no other adverse translational kinematics. However, an unrepaired or partially repaired T-capsulotomy resulted in increased rotational ROM and ML translation.

Conclusion

The results of this study show that complete capsular repair following interportal or T-capsulotomy adequately restores rotational ROM and joint translation to near intact levels.
Clinical Relevance: Where feasible, complete capsular closure should be performed, especially following T-capsulotomy. However, further clinical evaluation is required to determine if adverse kinematics of an unrepaired capsule are associated with patient reported outcomes.