Hip Capsular Closure: A Biomechanical Analysis of Failure Torque

Abstract

Background: Hip capsulotomy is routinely performed during arthroscopic surgery to achieve adequate exposure of the joint. Iatrogenic instability can result after hip arthroscopic surgery because of capsular insufficiency, which can be avoided with effective closure of the hip capsule. There is currently no consensus in the literature regarding the optimal quantity of sutures upon capsular closure to achieve maximal stability postoperatively. Purpose/Hypothesis: The purpose of this study was to determine the failure torques of 1-, 2-, and 3-suture constructs for hip capsular closure to resist external rotation and extension after standard anterosuperior interportal capsulotomy (12 to 3 o’clock). Additionally, the degree of external rotation at which the suture constructs failed was recorded. The null hypothesis of this study was that no significant differences with respect to the failure torque would be found between the 3 repair constructs. Study Design: Controlled laboratory study. Methods: Nine pairs (n = 18) of fresh-frozen human cadaveric hemipelvises underwent anterosuperior interportal capsulotomy, which were repaired with 1, 2, or 3 side-to-side sutures. Each hip was secured in a dynamic biaxial testing machine and underwent a cyclic external rotation preconditioning protocol, followed by external rotation to failure. Results: The failure torque of the 1-suture hip capsular closure construct was significantly less than that of the 3-suture construct. The median failure torque for the 1-suture construct was 67.4 N·m (range, 47.4-73.6 N·m). The median failure torque was 85.7 N·m (range, 56.9-99.1 N·m) for the 2-suture construct and 91.7 N·m (range, 74.7-99.0 N·m) for the 3-suture construct. All 3 repair constructs exhibited a median 36° (range, 22°-64°) of external rotation at the failure torque. Conclusion: The most important finding of this study was that the 2- and 3-suture constructs resulted in comparable biomechanical failure torques when external rotation forces were applied to conventional hip capsulotomy in a cadaveric model. The 3-suture construct was significantly stronger than the 1-suture construct; however, there was not a significant difference between the 2- and 3-suture constructs. Additionally, all constructs failed at approximately 36° of external rotation. Clinical Relevance: Re-establishing the native anatomy of the hip capsule after hip arthroscopic surgery has been reported to result in improved outcomes and reduce the risk of iatrogenic instability. Therefore, adequate capsular closure is important to restore proper hip biomechanics, and postoperative precautions limiting external rotation should be utilized to protect the repair.