Borderline Hip Dysplasia Shows Significantly Improved Clinical and Radiographic Outcome When Treated With Periacetabular Osteotomy, With or Without Concomitant Hip Arthroscopy.

PURPOSE: To analyze the patient-reported outcome measures and radiological results of patients with borderline hip dysplasia (BHD) treated with isolated periacetabular osteotomy (PAO) and to compare it with a control group of patients treated with PAO plus adjuvant hip arthroscopy. METHODS: We retrospectively analyzed PAO cases from 2016 to 2023, of which 73 were classified as BHD, defined as lateral center-edge angle >20°, anterior wall index ≤0.3, and/or posterior wall index ≤0.85, and any tomographic acetabular sector angle below the threshold proposed by Verhaegen et al. Patients were grouped depending on the use of concomitant hip arthroscopy or not at the time of PAO and subclassified using a modified Ottawa classification: anterior-wall-deficient, posterior-wall-deficient, and both-wall-deficient hips (anteroposterior-wall-deficient hips). Outcome measures included modified Harris Hip Score, Hip Disability and Osteoarthritis Outcome Score, and University of California Los Angeles scores, angular correction, and postoperative complications (Clavien-Dindo classification). RESULTS: A total of 223 patients were initially analyzed, with 73 classified as BHD. Thirty-six patients were included in the arthroscopy group and 37 in the without-arthroscopy group. The mean follow-up of the concomitant arthroscopy group was 44.1 months (range, 37.2-52.1), whereas that of the nonarthroscopy group was 49.4 months (range, 36.6-66.7; P = .34). Significant postoperative improvements were observed in the modified Harris Hip Score (63.3 ± 8.8-93.1 ± 8.0), Hip Disability and Osteoarthritis Outcome Score (61.6 ± 8.3-92.3 ± 8.5), and University of California Los Angeles (7 [6.00; 7.00] to 9.00 [9.00; 9.00]) scores (all P < .01). Achievement rates for minimal clinically important difference and patient acceptable symptom state exceeded 95% for both modified Harris Hip score and Hip Disability and Osteoarthritis Outcome Score, whereas substantial clinical benefit was achieved by approximately 70% of patients. No significant differences were observed between the arthroscopy and nonarthroscopy groups across any clinical outcome or radiographic correction (all P > .05). Twenty-five complications occurred, with 3 reoperations for implant removal. CONCLUSIONS: PAO showed excellent early clinical and radiological outcomes in borderline dysplasia, regardless of the use of concomitant hip arthroscopy or anatomical subtype of BHD. LEVEL OF EVIDENCE: Level III, retrospective comparative case series.