Biomechanical Stability of the Hip Is Impacted by Choice of Partial or Complete Closure of the Capsule Following a Periportal Capsulotomy: An In Vivo Time-Zero Comparison.

Abstract

To evaluate the in vivo biomechanical effects of periportal capsulotomies, single (modified anterior portal [MAP]) portal repair, and complete (MAP + anterolateral portal [ALP]) repair on altering the resistance to axial distraction compared to the native state (i.e., precapsulotomy). Consecutive patients undergoing primary hip arthroscopy with periportal capsulotomies received intraoperative axial distraction testing at 0, 50, and 100 pounds of force (lbf). Patients were excluded if they did not break their suction seal with 100 lbf. Distraction testing was performed prior to capsulotomy (native), postcapsulotomy, after repair of just the MAP (partial repair), and after repair of both the MAP and ALP (complete repair). Distraction distances were calculated in millimeters (mm) as the difference in joint space between 0 and 50 or 100 lbf on intraoperative fluoroscopy from the lateral sourcil edge of the acetabulum to the femoral head. Repeated measures analysis of variance and Bonferroni-corrected P values were used for comparison. Eighty-six patients were included (58% female; mean age, 33.6 ± 11.7 years). There was a significant increase in distraction distance in the unreparied capsulotomy state compared to the native state at 100 lbf (1.14 [0.33-1.96] mm, P = .03). After partial and complete repair, the distraction distance was significantly decreased compared to the native state at 100 pounds of traction by 1.09 mm (0.28-1.90, P < .001) and 2.84 mm (2.09-3.59, P < .001), respectively. In a subgroup analysis, males also had a substantial decrease in distraction distance with MAP closure alone compared to the native state at 100 lbf (1.33 [0.32-2.35] mm, P = .04), whereas females did not (0.92 [0.09-1.75] mm, P = .19). The periportal capsulotomy causes a significant increase in hip distractibility compared to the native state, and both partial and complete capsular repair restore distraction resistance to levels at or greater than the native state. Level IV, retrospective case series.