Comparative Reliability of 3-Tesla Magnetic Resonance Imaging to Arthroscopy Findings in Femoroacetabular Impingement

Abstract

Purpose: We have found that 3-tesla magnetic resonance imaging (3TMRI) is as clinically effective as magnetic resonance (MR) arthrogram when it comes to investigating patients with femoroacetabular impingement (FAI). It is also a noninvasive procedure that can be done more efficiently, with equivalent radiological and surgical outcomes. We would recommend 3TMRI as the primary investigation for patients presenting with FAI-type symptoms. Methods: This was a retrospective review of a single surgeon series of 59 operative cases, over 3 years. The inclusion criteria were arthroscopically confirmed diagnosis of FAI and preoperative imaging with 3TMRI scans. The surgical reports were analyzed and compared to the radiological reports, that were produced independently by two consultant musculoskeletal radiologists. The key findings included were the presence of labral tear, femoral CAM deformity, and acetabular and femoral cartilage damage. Results: We found that 3T MRI is sensitive in detecting the presence of labral tears and CAM deformities. (96% and 83% respectively). It was however, less sensitive in detecting femoral and acetabular cartilage damage. (50% and 69% respectively). The specificity of excluding cartilage wear on both the femoral and acetabular side was also high, (83% and 86%) but low for labral tears and CAM deformities (9% and 69%). The positive predictive value of 3TMRI was high in labral tears, CAM deformities, and acetabular wear (82%, 74%, and 97%) but low in predicting femoral cartilage damage (25%). The negative predictive value was high in detecting CAM lesions and femoral wear (80% and 94%) but low for labral tears and acetabular wear (33% and 27%). Conclusion: 3T MRI is particularly good at detecting the presence of labral tears, and CAM deformities. It is less sensitive at detecting cartilage damage, but more accurate in diagnosing the location of cartilage wear when present. This is a level 3 study, being a retrospective case–control study. The clinical relevance of this study is to determine if the less invasive 3TMRI study can be used to substitute for MR arthrography in the diagnosis of FAI in patients.