Application of T2 mapping to assess articular cartilage in patients at risk of developing chondromalacia

BACKGROUND: Chondromalacia is a common pathology of joints, leading to a decrease in the patient's quality of life. Magnetic resonance imaging is the method of choice for the diagnosis of articular cartilage defects [1]. T2 mapping of cartilage is a non-invasive quantitative technique that allows estimation of its T2-relaxation time, which may be relevant in cases where articular cartilage surveillance is recommended [2–5]. AIM: To study the magnetic resonance characteristics of knee cartilage using a routine protocol and T2 mapping technique in patients at risk of chondromalacia. MATERIALS AND METHODS: Magnetic resonance research of the knee joint was prospectively performed on 35 patients aged 18–70 years who signed informed voluntary consent in the period from 2022 to 2023. The study was approved by the local ethical committee of International Tomography Center (Novosibirsk, Russia). Exclusion criteria: exacerbation stage of comorbid diseases, knee joint osteoarthritis of stages 3–4. The main group consisted of patients with signs of chondromalacia; the group with initial degenerative changes — of patients with local areas of thinning and/or changes in the signaling characteristics of articular cartilage with minor/no degenerative changes of the joint. The control group consisted of patients without changes in cartilage signaling characteristics, traumatic and degenerative changes of the knee joint. The study of the knee joint was performed on a Philips INGENIA magnetic resonance tomograph (1.5T intensity) using the routine protocol: T2-weighted images, PD-SPAIR, PD-weighted images, T1-weighted images and T2 mapping technique with calculation of the T2-relaxation time of the cartilage tissue. Statistical analysis was performed using non-parametric research methods (Mann–Whitney U-test, Spearman correlation coefficient). The critical level of significance (p) is 0.05. RESULTS: The median age in the control group was 28.0 [24.0; 38.0] years, in the main group 48.0 [37.2; 55.7] years, and in the group with initial degenerative changes 48.0 [38.2; 59.5] years. Analysis of the localization of the cartilage defect of the knee joint revealed that chondromalacia was determined on the medial facet of the patella in 11 (91.6%) patients, on the lateral facet of the patella in 4 (33.3%) patients, and on the medial femoral condyle in 4 (33.3%) patients. When measuring cartilage thickness, a high individual variability of values was revealed with its significant decrease only in the defect area (p 0.05), with no significant differences between the groups in the other sections (p 0.05). When evaluating the values of cartilage T2-relaxation time, its statistically significant increase was revealed in the area of patella cartilage in patients from the main group and with initial degenerative changes (p 0.001 and p 0.01), cartilage of medial femoral condyle in patients with initial degenerative changes (p 0.05) in comparison with the control group. Correlation analysis between cartilage thickness and T2-relaxation time was performed, significant pairs were found: in the control group — in the area of lateral femoral condyle (p=0.011, r=0.636), in the main group — on the medial facet of the patella (r=–0.591, p=0.043), and in the area of medial femoral condyle (r=–0.760, p=0.004). In other cases, no significant correlations between cartilage thickness and patient groups were found. CONCLUSION: A statistically significant local increase in the T2-relaxation time in the patient groups revealed in comparison with the control group at high variability of cartilage thickness. The presented results indicate that the predominant diagnostic criterion is the change in signaling characteristics and increase in T2-relaxation time in the cartilage structure.