Magnetic resonance arthrography for femoroacetabular impingement surgery: is it reliable?

BACKGROUND: Magnetic resonance arthrography (MRA) is commonly used to demonstrate injury to the labrum and hyaline cartilage in patients with femoroacetabular impingement (FAI). The purpose of this study was to assess the diagnostic correlation between MRA and findings at arthroscopic and open surgery. MATERIALS AND METHODS: MRA reports of 41 hips with symptomatic FAI were reviewed and compared with subsequent intraoperative findings (n = 21 surgical dislocations and n = 20 therapeutic hip arthroscopies). Each case was assessed for the presence of a cam deformity, a cartilage lesion of the femoral head, an os acetabuli, an injury to the labrum and injury to the acetabular cartilage. Results were collected prospectively in a cross-table and analysed retrospectively for sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). RESULTS: The sensitivity, specificity, PPV and NPV in the presence of reported cam-type deformity or an os acetabuli were 100 %. In the presence of cartilage lesions of the femoral head, the values were 46, 81, 55 and 73 %, respectively. For labral tears, the values were 91, 86, 97 and 67 %. In the presence of acetabular cartilage injuries, the values were 69, 88, 78 and 81 %, respectively. CONCLUSIONS: MRA appears to be an efficacious imaging modality in the evaluation of labral tears, cam-type impingement lesions and os acetabuli of the hip. MRA is less efficacious in the diagnosis of cartilage abnormalities in the hip, both femoral and acetabular. Researchers should focus on further improvements in imaging techniques in order to give reliable preoperative information to the surgeon.