The Effect of Capsulotomy and Capsular Repair on Hip Distraction: A Cadaveric Investigation

Purpose: To quantify how increasing interportal capsulotomy size affects the force required to distract the hip and to biomechanically compare simple side-to-side suture repair to acetabular-based suture anchors as capsular repair techniques. Methods: Twelve fresh-frozen cadaveric hip specimens were dissected to the capsuloligamentous complex of the hip joint and fixed in a material testing system, such that a pure axial distraction of the iliofemoral ligament could be achieved. After each hip in was tested an intact state, sequential distraction was tested with 2, 4, 6, and 8 cm capsulotomies. Specimens were assigned randomly to be repaired with either 4 side-to-side suture repair (n = 6) or 2 doubleloaded all-suture anchors (n = 6). The distraction force as well as the relative distraction force percentage normalized to the intact capsule were compared between suture repair and suture anchor repair groups. Results: Increasing the size of the capsulotomy resulted in less force required to distract the hip to 6 mm. The force decreased as the capsulotomy was extended with statistical significance in distraction force seen between the intact state and the 4 cm (P = .003), 6 cm (P < .001), and 8 cm (P .001) pound capsulotomy but not for the intact state compared to the 2 cm capsulotomy (P = .28). Statistical significance in relative distraction force was seen for each of the capsulotomy conditions (P < .001 for all conditions compared with the intact state). The side-to-side suture repair construct (104.3% of intact force) required greater force to distraction to 6 mm compared with the suture anchor repair (87.1% of intact force) (P = .008). Conclusions: An interportal capsulotomy significantly affected the force required to distract the hip in a cadaveric model, with the larger the size of capsulotomy resulting in less force required to distract the hip. When we performed an interportal capsulotomy, the iliofemoral ligament strength was altered significantly but capsular repair with either side-to-side sutures or suture anchor-based repair was able to restore the capsular strength to a native intact hip. We found, however, that the side-toside suture repair was better able to restore the distraction force compared with suture anchor repair.