Borderline Hip Dysplasia Not Associated With Significant Differences in Hip Survivorship or Patient-Reported Outcomes After Primary Hip Arthroscopy for Femoroacetabular Impingement Syndrome: A Propensity-Matched Cohort Study With Minimum 10-Year Follow-up

Background: Hip arthroscopy has demonstrated favorable short- and mid-term outcomes for femoroacetabular impingement syndrome (FAIS) in patients with borderline hip dysplasia (BHD). However, long-term outcomes in patients with FAIS and BHD treated with hip arthroscopy remain understudied. Purpose: To evaluate hip survivorship and patient-reported outcomes (PROs) in patients with FAIS and BHD compared with those without BHD at a minimum 10-year follow-up. Study Design: Cohort Study; Level of evidence, 4. Methods: A retrospective matched-cohort study was conducted on patients undergoing primary hip arthroscopy for FAIS by a single surgeon (2012-2024). BHD was defined as a lateral center-edge angle (LCEA) of 20° to 25°. Patients with BHD were matched 1 to 2 to controls without BHD based on age, sex, body mass index, and preoperative modified Harris Hip Score (mHHS). Radiographic parameters (eg, alpha angle, LCEA) were assessed pre- and postoperatively. PROs—including mHHS, Non-Arthritic Hip Score (NAHS), and hip survivorship (revision arthroscopy, conversion to total hip arthroplasty [THA])—were compared. Results: The study included 23 patients with BHD (mean age, 33.6 years; 69.6% women) and 46 controls (mean age, 32.7 years; 65.2% women). Both groups showed significant improvements in mHHS and NAHS at 10 years (all P < .001), with no differences in postoperative scores or minimal clinically important difference achievement (BHD group, 91.3% vs control group, 97.5%; P = .55). There were no conversions to THA in the BHD group and 2 in the control group (4.3%; P = .189). Revision arthroscopy rates were 0% in the BHD group and 8.7% in the control group ( P = .549). Patients with BHD exhibited significantly greater reductions in alpha angles on 45° Dunn views (−13° vs −1.9°; P = .01). Conclusion: At a minimum 10-year follow-up, patients with BHD who underwent hip arthroscopy for FAIS achieved comparable PROs and hip survivorship to those without BHD. These findings support the use of hip arthroscopy as a durable and effective treatment for FAIS in this population.