Comparison of Interportal and Periportal Capsulotomies and Axial Distraction Resistance During Hip Arthroscopy: An In Vivo Propensity-Matched Cohort Study

Background: Intraoperative hip capsule management is increasingly recognized as an important component of hip arthroscopy for the prevention of capsular-related instability. The periportal capsulotomy, relative to the interportal capsulotomy, has been proposed as a minimally invasive technique for decreasing postarthroscopy hip instability; however, the biomechanical effects of this technique are not well established. Purpose/Hypothesis: This study aimed to provide a biomechanical characterization of interportal and periportal capsulotomies, helping inform surgeon choice of capsulotomy type and repair, potentially guiding clinical practice in hip arthroscopy. The authors hypothesized that the periportal capsulotomy would demonstrate greater resistance to axial distraction in all capsular states. Study Design: Cross-sectional study; Level of evidence, 3. Methods: Patients undergoing primary hip arthroscopy by a single surgeon underwent intraoperative axial distraction testing at 25-, 50-, 75-, and 100-pound force intervals, with each axial distraction distance measured by standardized fluoroscopic evaluation. Propensity matching was conducted between the periportal group and the interportal group using native state distraction, lateral center-edge angle, and sex as covariates to achieve balance between groups. Between-group comparisons of distraction distances were then conducted using the Student t test and Fisher exact test. Results: In total, 74 interportal capsulotomies and 124 periportal capsulotomies were identified. Propensity matching yielded 74 hips in each group. Demographic and radiographic characteristics were similar between matched cohorts ( P > .05). An unrepaired interportal capsulotomy led to an increase in hip distraction of 2.74 mm at 100 lbf ( P < .001) compared with the native state, whereas unrepaired periportal capsulotomy led to an increase of 2.43 mm at 100 lbf ( P < .001). Distraction distances were similar between the interportal and periportal groups in both the capsulotomy and repair states ( P > .05), while the periportal capsulotomy repair demonstrated decreased hip distraction distance when compared with the native state by 1.37 mm at 75 lbf and 1.45 mm at 100 lbf ( P < .001). Conclusion: In a propensity-matched cohort analysis, an unrepaired periportal capsulotomy and interportal capsulotomy have similar effects on increasing hip axial distraction distance intraoperatively. Performing a capsular repair restores intraoperative resistance to axial distraction in both procedures. Despite the minimal disruption of the capsule with periportal techniques, repair is required for restoration of native biomechanics.