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: Twentyfour biomechanical studies were included that 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 ROM, and torsional stability when compared to capsular release. Significant differences were observed between capsular repair and release in total ROM in the coronal plane with improved stability in the repair groups (standardized mean difference [SMD]: -1.3 degrees, 95% confidence interval [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 degrees (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. Clinical Relevance: Investigating the biomechanical outcomes of capsular repair and reconstruction will help surgeons better understand the rationale and implications of these capsular management strategies.