Cartilage collagen structure upon knee joint distraction and high tibial osteotomy as measured with T2-mapping MRI - post-hoc analyses of two RCTs

High tibial osteotomy (HTO) and knee joint distraction (KJD) are joint-preserving treatments for knee osteoarthritis (OA) that have shown good clinical results and cartilage thickness increase. In this exploratory study, cartilage T2 relaxation times, as a measure of collagen structure, are evaluated after both treatments, and compared to natural OA progression. Ten patients indicated for total knee arthroplasty (TKA) were treated with KJD (KJDTKA). Thirty patients indicated for HTO were treated with KJD (KJDHTO; n = 10) or HTO (n = 20). 3T T2-mapping MRI scans were performed before and one (KJD groups only) and two years after treatment, from which cartilage was segmented and the volume and T2 relaxation times were calculated. Patients were matched with untreated patients from the Osteoarthritis Initiative (OAI) to compare the change in T2 values over time. KJDHTO (n = 8) and HTO (n = 17) patients both showed statistically significant increases in T2 values (worsening) but no volume changes. KJDTKA patients (n = 8) only showed a tendency for (first-year) T2 value increase, and a significant volume increase in the most affected compartment (MAC). There were no significant differences between the three groups. All treated patients combined showed a significantly higher increase in T2 times than untreated patients from the OAI for both femur and tibia. KJD and HTO cause an increase in cartilage T2 relaxation times, which could indicate loss or reorganization of collagen structure integrity. In TKA-indicated KJD patients, this goes paired with volume increase, indicating it may be the result of maturation of newly formed cartilage.