Outcome for Arthroscopic Treatment of Anterior Inferior Iliac Spine/Subspine Related Hip Impingement

OBJECTIVES: Extra-articular disorders of the hip are under-recognized and under-reported. Extra-articular forms of hip impingement can include anterior inferior iliac spine (AIIS) related subspine impingement. The purpose of this study was to investigate the outcome after arthroscopic treatment of anterior inferior iliac spine (AIIS)/Subspine related hip impingement. METHODS: A prospective institutional hip preservation registry was reviewed to identify patients that underwent isolated arthroscopic AIIS decompression. Primary outcome tools captured in the registry included: the modified Harris Hip Score (mHHS), the Hip Outcome Score (HOS) and the international Hip Outcome Tool (iHOT-33). Patients with minimum one-year follow-up were included. Meaningful outcome improvement was determined based on minimal clinically important difference (MCID). Statistical analyses were primarily descriptive. RESULTS: Thirty-three patients with mean follow-up 19.1 months (range: 12-44 months) were identified. All patients were female with a mean age of 26.1 (+ 10.3) years. All patients were found to have an associated labral tear and the mean acetabular version was increased at 2 and 3 o’clock (14.5 and 19.8 respectively). Mean pre-operative outcome scores on the mHHS, HOS activities of daily living (ADL), HOS Sport and iHOT-33 were 57.2 (SD+15.3), 66.9 (SD+18.8), 43.9 (SD+23.6) and 33.5 (SD+18.3) respectively. At final available follow-up, mean scores on these outcome measures were 79.5 (SD+19.0), 86.8 (SD+15.8), 70.4 (SD+32.8) and 65.0 (SD+31.0) respectively. By the one-year follow-up interval MCID had been achieved in the majority of patients across all four tools. CONCLUSION: There is a paucity of outcome evidence on AIIS/Subspine related hip impingement. This study demonstrates that isolated subspine impingement can be a cause of hip disability even in the absence of FAI. Patients with isolated subspine impingement are more likely to be women and they present with low patient reported outcome scores. Meaningful outcome improvement can be achieved however with arthroscopic AIIS decompression.