Inferior Patient‐Reported Outcomes After Primary Hip Arthroscopy in the Congenitally Narrow Joint Despite Similar Cartilage Quality When Compared With a Propensity‐Matched Control Group

PURPOSE: To evaluate the outcomes after hip arthroscopy in patients with a symmetric congenitally narrowed hip joint space without radiographic evidence of degenerative changes. METHODS: Consecutive patients with Tönnis grade 0 undergoing hip arthroscopy between 2009 and 2022 for femoroacetabular impingement syndrome with labral repair and minimum 2-year postoperative outcomes were eligible for inclusion in the study. Subjects were considered congenitally narrowed if they had an average bilateral joint space width less than 3 mm without other radiographic evidence of osteoarthritis. This cohort was propensity-matched to patients with an average joint space greater than 4 mm. Preoperative demographic and radiographic variables, intraoperative findings and procedures, and postoperative outcomes were compared between the 2 groups. RESULTS: Thirty-one patients in the congenitally narrow group were propensity-matched to 57 patients in the control cohort. The groups were comparable in age, gender, body mass index, and radiographic variables other than joint space width between cohorts. The congenitally narrow group had no differences in femoral head or acetabular chondral damage compared with the control cohort (P > .05 for both). There were significantly lower postoperative patient-reported outcomes in the congenitally narrow group across multiple patient reported outcome measures. At 5-year time point, the control group had a significantly higher percentage, meeting patient acceptable symptomatic state for modified Harris Hip Score (80% vs 52%, P = .01) and International Hip Outcome Tool-12 (80% vs 56%, P = .03) and minimal clinically important difference for modified Harris Hip Score (89.5% vs 63%). There was no difference in revision arthroscopy (9.7% vs 10.5%, P = .9) or arthroplasty-free survivorship (100% vs 96.5%; P = .29) between the congenitally narrow and control groups, respectively. CONCLUSIONS: There were no differences in intraoperative cartilage quality or reoperation rate in patients with a congenitally narrow joint compared with a propensity-matched control cohort. However, despite the lack of radiographic osteoarthritis, patients with a congenitally narrow joint had inferior patient-reported outcomes scores compared with the study control group. LEVEL OF EVIDENCE: Level III, retrospective cohort study.