A pilot study with 3D T1?-mapping for quantitative evaluation of cartilage after open-wedge high tibial osteotomy

Purpose: To evaluate the recently developed three-dimensional (3D) T1 rho-mapping technique for the quantitative evaluation of cartilage changes after open-wedge high tibial osteotomy (OWHTO). Method: Eleven patients with medial knee osteoarthritis and spontaneous osteonecrosis of the medial femoral condyle underwent T1 rho magnetic resonance imaging. The full-thickness cartilage of the medial femoral condyle (MFC), lateral femoral condyle, medial tibial condyle, and lateral tibial condyle, and the trochlea and patella were set as regions of interest; mean T1 rho values were calculated using two-dimensional (2D) and 3D analyses. The state of cartilage injury was evaluated using the International Cartilage Repair Society grading system (ICRS grade). T1 rho values before OWHTO and after hardware removal were compared using the Wilcoxon signed-rank test. The correlation between T1 rho values and the ICRS grade was explored using the Spearman rank correlation coefficient. Results: Cartilage repair at the MFC was observed in a high proportion of patients (82%), but 2D analysis did not reveal a significant difference after surgery at any site. In contrast, 3D analysis revealed a significant decrease in T1 rho values after surgery at the MFC (before surgery: 44.1 ms; after surgery: 38.9 ms; p = 0.016), but no significant difference at any other site. In the MFC, there was a positive correlation between 3D T1 rho values and arthroscopic findings before and after surgery (rs = 0.62, p < 0.01), which was absent from the 2D T1 rho values. Conclusions: 3D T1p-mapping may be an effective tool for detecting changes in cartilage quality after OWHTO.