Accuracy of non-arthrographic 3T MR imaging in evaluation of intra-articular pathology of the hip in femoroacetabular impingement

Abstract

Objective: To investigate the accuracy of non-arthrographic 3-T MRI compared to hip arthroscopy in the assessment of labral and cartilaginous pathology in patients with suspected FAI.

Materials and methods: Following IRB approval and waived consent, 42 consecutive cases of suspected FAI with non-arthrographic 3-T MRI and arthroscopy of the hip were reviewed. High-resolution TSE MR imaging was evaluated in consensus by two musculoskeletal radiologists, blinded to arthroscopic findings, for the presence of labral tears and articular cartilage lesions. Acetabular cartilage was categorized as normal, degeneration/fissuring, delamination, or denudation. MRI findings were compared to arthroscopy. Sensitivity, specificity, accuracy, and predictive values for MRI were calculated using arthroscopy as the standard of reference.

Results: Forty-two hips in 38 patients with a mean age of 29 (range 13-45 years) were assessed. Mean interval between MRI and arthroscopy was 154 days (range 27-472 days). MRI depicted 41 cases with labral tears (sensitivity 100%, specificity 50%, accuracy 98%, PPV 98%, NPV 100%), 11 cases with femoral cartilage abnormalities (sensitivity 85%, specificity 100%, accuracy 95%, PPV 100%, NPV 94%), and 36 cases with acetabular cartilage lesions (sensitivity 94% specificity 67%, accuracy 90%, PPV 94%, NPV 67%). Of the 36 cases with acetabular cartilage lesions on MRI, 7 were characterized as degeneration/fissuring, 26 as delamination, and 3 as denudation, with discordant results between MRI and arthroscopy for grading of articular cartilage in ten cases.

Conclusion: Non-arthrographic 3-T MR imaging is a highly accurate technique for evaluation of the labrum and cartilage in patients with clinically suspected FAI.

Keywords: Acetabular labrum; Cartilage; Femoroacetabular impingement; Hip; Magnetic resonance imaging.