Pathological findings in patients with low anterior inferior iliac spine impingement

Femoroacetabular impingement (FAI) has been well described in recent years as one of the major causes of hip pain potentially leading to acetabular labral tears and cartilage damage, which may in turn lead to the development of early degenerative changes. More recently, extra-articular patterns of impingement such as the anterior inferior iliac spine (AIIS)/subspine hip impingement have gained focus as a cause of hip pain and limitation in terminal hip flexion and internal rotation. The purpose of this study was to evaluate the prevalence of low AIIS in patients undergoing hip arthroscopy and to characterize the concomitant intra-articular lesions.

Between November 2011 and April 2013, 100 consecutive patients underwent hip arthroscopy for various diagnoses by a single surgeon. After intra-operative diagnosis of low AIIS was made, a comprehensive review of the patients' records, preoperative radiographs, and intra-operative findings was conducted to document the existence and location of labral and chondral lesions.

Twenty-one (21 %) patients had low AIIS. There were 13 males (mean age 38.4 years) and eight females (mean age 35.5 years). Eight patients had pre-operative radiographic evidence of low AIIS. All patients had a labral tear anteriorly, at the level of the AIIS; 17 had chondrolabral disruption and 17 had chondral lesions in zone two (antero-superior); and four patients had lesion in zones two and three.

Low AIIS is a common intra-operative finding in hip arthroscopy patients. Characteristic labral and chondral lesions are routinely found in a predictable location that effaces the low AIIS. Level of Evidence-Level IV, Case Series.