MRI findings of femoroacetabular impingement

OBJECTIVE. The purpose of our study was to evaluate MRI in the identification of labral and articular cartilage lesions in patients with a clinical suspicion of femoroacetabular impingement. MATERIALS AND METHODS. Preoperative MRI was performed in 46 consecutive patients (26 men, 20 women; age range, 21-45 years; mean age, 32.3 years) for whom femoroacetabular impingement was clinically suspected. Two musculoskeletal radiologists independently assessed the MR images for the presence and anatomic site of labral disorders, labral-chondral transitional zone disorders, femoral cartilage lesions, and acetabular cartilage lesions. Surgical correlation was obtained in all cases by two surgeons who were experienced in hip arthroscopy. RESULTS. Seven patients showed labral tears on MRI that were confirmed surgically in all cases. Thirty-seven patients (97%) of the 38 surgically confirmed cases had lesions of the labral-chondral transitional zone on MRI. The sites of labral-chondral transitional zone abnormalities at arthroscopy were 50% anterosuperior, 36% anterosuperior and superolateral, 11% superolateral, and 3% superolateral and posterosuperior. The site was identified correctly in 92% (reviewer 1) and 95% (reviewer 2) of cases on MRI. Separate acetabular cartilage abnormality was surgically identified in 39% of cases, and femoral cartilage lesions were found in 20%. The acetabular chondral lesions were correctly identified in 89-94% of cases. CONCLUSION. MRI provides a useful assessment of patients in whom a femoroacetabular impingement is clinically suspected. A high-resolution, nonarthrographic technique can provide preoperative information regarding the presence and anatomic site of labral and cartilage abnormalities.