Background Arthroscopic surgery for borderline developmental dysplasia of the hip (BDDH) remains controversial.

Objective To observe the effect of hip arthroscopy surgery for BDDH after more than 2 years of operation, and explore the effect of arthroscopic surgery for BDDH.

Methods A retrospective analysis was performed in BDDH patients who underwent arthroscopic surgery in the First Medical Center of Chinese PLA General Hospital from September 2016 to June 2020. Based on the preoperative imaging and intraoperative pathological findings, corresponding managements were conducted. By April 2023, the modified Harris hip score (mHHS), international hip outcome score -12 (IHOT-12), visual analog scale (VAS), and patient's satisfaction score were assessed via questionnaire star with telephone before operation and at two years after operation.

Results Totally 52 patients were included in the study, including 15 males and 37 females. The mean age was 30.75 ± 8.39 years, and the mean LCEA was 21.97° ± 2.14°. The incidence of intraoperative labral tear, acetabular and femoral head cartilage injury was 100%, 44.23% and 32.69%, respectively. All patients underwent acetabular minimal rim trimming with labral repair and fixation, and capsular closure after capsulotomy. The incidence of Cam deformity removal and abnormal anterior inferior iliac spine (AIIS) decompression was 88.46% and 57.69%, respectively. The mean postoperative follow-up was 44.35 ± 10.96 months, and the mHHS score (82.88 ± 9.15 vs 44.38 ± 15.05), iHOT-12 score (83.62 ± 9.59 vs 41.18 ± 13.20) and VAS score (1.83 ± 1.02 vs 6.42 ± 1.29) were all significantly improved compared with those before operation (P<0.01).

Conclusion BDDH is mainly caused by mechanical factors of labrum and cartilage injury. The labrum repair and fixation based on the acetabular minimal rim trimming, Cam deformity sufficient removal, type 2-3 AIIS decompression and capsular closure are performed to obtain satisfactory clinical results.