Do Borderline Hips Show a Similar Response to Periacetabular Osteotomy as Frank Hip Dysplasia? A Cohort Study.

Abstract

Periacetabular osteotomy (PAO) is increasingly considered a treatment option for symptomatic borderline hip dysplasia (BHD) with a lateral center edge angle (LCEA) of 20°-25°. However, whether BHD hips are likely to benefit from PAO compared to truly dysplastic hips (LCEA <20°) remains unclear. The aim of this study was to compare the short-term outcome of PAO in borderline hip dysplasia to frank dysplasia. A prospective PAO database was utilized. A total of 230 hips with a minimum follow-up of 1 year that had undergone PAO by a single surgeon between January 2022 and December 2024 were included in this study. Patients were divided into BHD and frank dysplasia based on LCEA. The University of California and Los Angeles activity scale (UCLA), Hip Disability and Osteoarthritis Outcome Score - Physical Function Short Form (HOOS-PS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), International Hip Outcome Tool-12 (iHOT-12), Harris Hip Score (HHS), modified Harris Hip Score (mHHS), German Forgotten Joint Score (G-FJS) and Postel Merle d'Aubigné (PMA) score were assessed at a mean follow-up of 17 - 21 months. Postoperative PROMs were compared between groups using unadjusted analyses and multivariable linear regression models adjusting for baseline PROMs, demographic factors, radiographic parameters and concomitant procedures. Most patient-reported outcome measures (PROMs) differed significantly preoperatively and were inferior in the BHD group. All PROMs improved significantly in both groups at follow-up. No statistically significant between-group differences were observed at final follow-up. In multivariable regression analyses, dysplasia severity was not associated with postoperative outcomes for any PROM. The improvement in UCLA was statistically significantly greater in the BHD group (p=0.043). Patients with BHD benefit from PAO with a magnitude of improvement comparable to frank dysplasia. After adjustment, dysplasia severity was not an independent predictor of outcome, indicating comparable short-term clinical benefit between groups. Level III.