Hip Capsular Management in Patients with Femoroacetabular Impingement or Microinstability: A Systematic Review of Biomechanical Studies

Purpose: To investigate the correlation between hip capsular management (repair or reconstruction) and biomechanical results in the setting of femoroacetabular impingement and microinstability.

Methods: A search of the PubMed and Embase databases was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Included studies focused on hip biomechanics related to capsular release, repair of I- and T-capsulotomy, or capsular reconstruction. Studies were assessed for external/internal rotation of the femur, femoral head translation, rotational torque, and distraction force.. Articles were excluded if they discussed treatment of the hip capsule related to surgical dislocation, mini-open surgery , arthroplasty, reorientation osteotomy, or traumatic dislocation.

Results: A total of 24 biomechanical studies were included which evaluated rotation/translation (11 studies), distraction (3 studies), the capsular role in microinstability (simulated with anterior capsule pie crusting [2 studies] and cyclical loading [2 studies]), allograft reconstruction (3 studies), and anatomic properties (3 studies). Repair and reconstruction demonstrated improvements in maximum distractive force, total range of motion, and torsional stability when compared to capsular release. Significant differences were observed between capsular repair and release in total range of motion in the coronal plane with improved stability in the repair groups (SMD: -1.3˚, 95% CI -1.68 , -0.854; p < .001). There was significantly increased total motion in the coronal plane in the capsular laxity state compared to the native state (SMD: 1.4˚ (95% CI 0.32, 2.49; p = .012).

Conclusions: Biomechanical evidence supports closure of the capsule after hip arthroscopy to reverse the significant effects of capsulotomy. Simulated capsule laxity models created altered joint motion and translation. Capsule reconstruction appears to restore the hip to its native capsule state.