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.

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.

Conclusions: 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.