Introduction. The role for hip arthroscopy (HS) in combination with periacetabular osteotomy (PAO) for the treatment of symptomatic acetabular dysplasia has not been clearly defined. In this study, we assessed midterm outcomes of concurrent hip arthroscopy and PAO (HS/PAO) for the treatment of symptomatic acetabular dysplasia with associated intra-articular pathology. Methods. We performed a retrospective review of concurrent HS/PAO cases in a prospectively collected institutional hip preservation database. From November 2005 to December 2012, 85 hips in 80 patients underwent combined HS/PAO. Two hips had a diagnosis other than acetabular dysplasia and 12 hips were lost to follow up, leaving 71 hips for analysis at mean 6.6-year follow-up (range 4–11 years). Hips were evaluated using the University of California, Los Angeles (UCLA) Activity Score, modified Harris Hip Score (mHHS), and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscore. Hips were stratified into preserved or failed groups, with failure defined as conversion to THA or a symptomatic hip (mHHS <70 or WOMAC pain subscore > 10). Complications were recorded and graded by the Clavien-Dindo classification. Regression analyses were performed to identify the interaction between patient factors, radiographic measures, and surgical details with outcome. Results. At final follow-up, two hips had undergone THA and an additional 15 hips were deemed symptomatic. 54 hips (76.1%) did not undergo conversion to THA or meet symptom thresholds, and this group had mean mHHS 92.1 ± 8.8, UCLA activity score 7.8 ± 2.1, and WOMAC pain subscore 1.8 ± 2.4. In univariate analysis, no patient factors, pre- or post-operative radiographic metrics, or intra-operative findings or procedures were associated with failure. There were 3 (4.2%) major complications (Clavien-Dindo Grade III or IV), and 5 patients underwent repeat surgery for recurrent symptoms (4 hip arthroscopy, 1
