Subregion-Specific T2-Cluster Analysis Reveals Early Cartilage Changes in Anterior Cruciate Ligament Reconstructed Knees

Motivation: To assess spatiotemporal changes of femoral cartilage in anterior cruciate ligament reconstructed (ACLR) patients from 3 weeks to 30 months using T2 relaxation times. Goal(s): Convert cartilage T2 into T2-clusters (longitudinally elevated T2 regions) across 5 femoral cartilage subregions (anterior, medial-central, medial-posterior, lateral-central, and lateral-posterior) and assess longitudinal changes. Approach: T2-clusters were categorized for femoral cartilage subregions in 15 ACLR subjects, their contralateral knees, and in 15 matched controls at 3 weeks, 3, 9, 18, and 30 months post-ACLR. Results: Anterior, lateral-posterior, and medial regions saw the greatest changes in T2-clusters across 30 months, with ACLR knees exhibiting larger changes compared to others. Impact: T2-clusters are better at detecting spatiotemporal variations in T2 within femoral cartilage subregions compared to bulk mean T2. T2-clusters are consistent with patterns of full-thickness defects observed in osteoarthritic cartilage, suggesting its potential application in monitoring cartilage health post-ACLR.