Association of Central Acetabular Osteophytes With Microinstability and Increased Combined Anteversion in Borderline Dysplasia Hips

Background: Central acetabular osteophytes (CAOs) have been implicated in abnormal hip biomechanics. However, their relationship with microinstability in borderline developmental dysplasia of the hip (BDDH) is unclear. Purpose/Hypothesis: The purpose of this study is to compare radiographic parameters between BDDH hips with and without CAOs and to determine whether CAOs are associated with microinstability. It was hypothesized that CAOs would correlate with increased version abnormalities and microinstability. Study Design: Case-control study; Level of evidence, 3. Methods: We retrospectively reviewed patients with BDDH, defined as a lateral center-edge angle of 18° to 25°, who underwent hip arthroscopy from 2020 to 2024. Patients were grouped as BDDH with CAO (cBDDH) or without CAO (nBDDH). Radiographic parameters, including anterior/posterior acetabular coverage, femoral neck version, acetabular version, and combined anteversion, were compared. Intraoperative findings of microinstability and ligamentum teres (LT) pathology were analyzed. Binary logistic regression identified predictors of CAO. Results: A total of 157 patients were included (cBDDH, 76; nBDDH, 81). The cBDDH group demonstrated higher rates of microinstability and LT tears, as well as increased femoral neck, acetabular, and combined anteversion. Logistic regression showed that microinstability (β = .027; P < .001), LT tear (β = .010; P = .001), and combined anteversion (β = 1.343; P = .029; R 2 = 0.542) were associated with CAO. Conclusion: In BDDH, CAOs were strongly associated with microinstability, LT tears, and increased combined anteversion. CAO may serve as a radiographic marker of instability and early osteoarthritis in BDDHs.