The Correlation Between Arthroscopically Defined Acetabular Cartilage Defects and a Proposed Preoperative Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage Index in Hips of Patients With Femoroacetabular Impingement Syndrome
Purpose: To evaluate a delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) index designed to predict focal acetabular articular cartilage damage in patients with femoroacetabular impingement (FAI).
Methods: The inclusion criteria were patients who underwent dGEMRIC and hip arthroscopy between April 2010 and August 2015 for FAI syndrome. The exclusion criteria were previous hip conditions, a Tönnis grade greater than 1, and a delay between magnetic resonance imaging and surgery greater than 180 days. The cutoff value for full-thickness chondral damage was set to 350 milliseconds. The coronal anterolateral (CAL) index was designed to evaluate focal articular anterolateral chondral defects. We calculated the binary classification test of the CAL index for full-thickness chondral damage, with arthroscopy as the gold standard. We calculated the correlation between the CAL index and the arthroscopically defined acetabular labrum articular disruption (ALAD) and Outerbridge grades and tested for differences between no or mild focal chondral damage and moderate or severe focal chondral damage. We repeated this analysis on the sagittal superior index, a combination of the sagittal anterior and posterior indices.
Results: A total of 195 hips (183 patients) were reviewed. The CAL index showed a sensitivity of 55% (95% confidence interval [CI], 32%-76%), specificity of 81% (95% CI, 74%-86%), positive predictive value of 27% (95% CI, 18%-37%), and negative predictive value of 93% (95% CI, 90%-96%). The CAL index showed a significant difference between no or mild focal chondral damage and moderate or severe focal chondral damage per both ALAD and Outerbridge groups (P < .0001). The CAL index was moderately inversely correlated with ALAD and Outerbridge grades (ρ = -0.403, P < .0001). The sagittal superior index was not significantly different between the groups and showed a weak correlation with focal defects.
Conclusions: The CAL index may play a role in ruling out full-thickness articular cartilage defects in patients with FAI syndrome. In addition, it may help in differentiating between no or mild focal chondral damage and moderate or severe focal chondral damage.