Magnetic Resonance Arthrography, a valuable pre-operative imaging modality in femoro-acetabular impingement

Background: The diagnostic accuracy of MR arthrography in preoperative assessment of labral tears and chondral abnormalities in femoroacetabular impingement patients. A non-randomized control study including 31 FAI patients (17 male and 14 females, mean age 31.9 years). All patients underwent MR arthrography after US-guided intra-articular contrast injection. Conventional and MR arthrography images were evaluated for bone abnormalities (including alpha angle and acetabular depth measurements), labral tears, and chondral abnormalities. The results were correlated to arthroscopy as the gold standard. Sensitivity, specificity, PPV, and NPV in the detection of labral tears and chondral abnormalities were statistically calculated. Results: The included FAI patients presented cam (mean age 30.4 years +/- 6.8 years), pincer (mean age 33.6 years +/- 9.8 years), and mixed (mean age 36.6 years +/- 12.9 years) types with the predominance of cam type. Cam type predominated in the male, while pincer and mixed types predominated in female patients. MR arthrography detected 41 labral tears in 23 patients with 87.5%, 71.4%, 91.3%, and 62.5% sensitivity, specificity, PPV, and NPV, respectively, and detected chondral abnormalities in 13 patients with 66.7%, 92.3%, 92.3%, and 66.7% sensitivity, specificity, PPV, and NPV, respectively. Conclusion: MR arthrography is a valuable imaging modality in preoperative assessment of FAI patients. Besides identifying the type of impingement through alpha angle and acetabular depth measurements, it detects labral tears with high sensitivity and PPV. Although less sensitive in detection of chondral abnormalities, our results showed high specificity.