Zonal T2* and T1(Gd) assessment of knee joint cartilage in various histological grades of cartilage degeneration: an observational in vitro study

OBJECTIVES: Accurate assessment of cartilage status is increasingly becoming important to clinicians for offering joint preservation surgeries versus joint replacements. The goal of this study was to evaluate the validity of three-dimensional (3D), gradient-echo (GRE)-based T2* and T1(Gd) mapping for the assessment of various histological severities of degeneration in knee joint cartilage with potential implications for clinical management. METHODS: MRI and histological assessment were conducted in 36 ex vivo lateral femoral condyle specimens. The MRI protocol included a 3D GRE multiecho data image combination sequence in order to assess the T2* decay, a 3D double-echo steady-state sequence for assessment of cartilage morphology, and a dual flip angle 3D GRE sequence with volumetric interpolated breathhold examination for the T1(Gd) assessment. The histological sample analysis was performed according to the Mankin system. The data were then analysed statistically and correlated. RESULTS: We observed a significant decrease in the T2* and T1(Gd) values with increasing grades of cartilage degeneration (p<0.001) and a moderate correlation between T2* (r=0.514)/T1(Gd) (r=0.556) and the histological grading of cartilage degeneration (p<0.001). In addition, we noted a zonal variation in the T2* and T1(Gd) values reflecting characteristic zonal differences in the biochemical composition of hyaline cartilage. CONCLUSIONS: This study outlines the potential of GRE-based T2* and T1(Gd) mapping to identify various grades of cartilage damage. Early changes in specific zones may assist clinicians in identifying methods of early intervention involving the targeted joint preservation approach versus moving forward with unicompartmental, bicompartmental or tricompartmental joint replacement procedures. TRIAL REGISTRATION NUMBER: DRKS00000729.