UCSF

In this study, quantitative magnetic resonance based measurements were used to evaluate T_1ρ and T₂ mapping and heterogeneity in femoroacetabular impingement (FAI) patients with acetabular cartilage delamination and to determine the ability of these quantitative MR-based measurements in detecting delamination. Unilateral hip joint MR-scans of 36 FAI patients with arthroscopically-confirmed acetabular cartilage delamination and 36 age, gender, and BMI matched controls were obtained. T_1ρ and T₂ mapping and heterogeneity of the hip joint articular cartilage were assessed in both groups using voxel-based relaxometry (VBR). Quantitative MR-based measurements were compared using statistical parametric mapping (SPM). Receiver operating characteristic (ROC) analysis was used to assess the ability of these quantitative measurements in detecting delamination by calculating the area under the curve (AUC). Pearson partial correlations (r) were used to assess for associations between T_1ρ and T₂ radial heterogeneity with the alpha angle in FAI patients. T_1ρ and T₂ global acetabular values were significantly higher in FAI patients with a focal increase within the posterior acetabular cartilage. FAI patients exhibited increased anterior superior acetabular T_1ρ and T₂ heterogeneity and both of these measures demonstrated a strong ability to detect acetabular cartilage delamination (T_1ρ AUC: 0.96, p < 0.001; T₂ AUC: 0.93, p < 0.001). FAI patients with a larger alpha angle exhibited increased anterior superior acetabular T_1ρ (r = 0.48, p = 0.02) and T₂ (r = 0.42, p = 0.03) heterogeneity. T_1ρ and T₂ heterogeneity within the anterior superior acetabular cartilage was shown to be a sensitive measure in detecting delamination and may prove beneficial to clinicians in determining optimal interventions for FAI patients. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:971-978, 2018.