dGEMRIC as a tool for measuring changes in cartilage quality following high tibial osteotomy: A feasibility study

Objective: The high tibial osteotomy (HTO) is an effective strategy for treatment of painful medial compartment knee osteoarthritis. Effects on cartilage quality are largely unknown. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) enables non-invasive assessment of cartilage glycosaminoglycan content. This study aimed to evaluate if dGEMRIC could detect relevant changes in cartilage glycosaminoglycan content following HTO. Design: Ten patients with medial compartment osteoarthritis underwent a dGEMRIC scan prior to HTO, and after bone healing and subsequent hardware removal. A dGEMRIC index (T1Gd) was used for changes in cartilage glycosaminoglycan content, a high T1Gd indicating a high glycosaminoglycan content and vice versa. Radiographic analysis included mechanical axis and tibial slope measurement. Clinical scores [Knee Osteoarthritis Outcome Scale (KOOS), visual analogue score (VAS) for pain, Knee Society Clinical Rating System (KSCRS)] before, 3 and 6 months after HTO and after hardware removal were correlated to T1Gd changes. Results: Overall a trend towards a decreased T1Gd, despite HTO, was observed. Before and after HTO, lateral femoral condyle T1Gd was higher than medial femoral condyle (MFC) T1Gd and tibial cartilage T1Gd was higher than that of femoral cartilage (P < 0.001). The MFC had the lowest T1Gd before and after HTO. Clinical scores all improved significantly (P < 0.01), KOOS Symptoms and QOL were moderately related to changes in MFC T1Gd. Conclusions: dGEMRIC effectively detected differences in cartilage quality within knee compartments before and after HTO, but no changes due to HTO were detected. Hardware removal post-HTO seems essential for adequate T1Gd interpretation. T1Gd was correlated to improved clinical scores on a subscore level only. Longer follow-up after HTO may reveal lasting changes.ClinicalTrials.gov registration ID: NCT01269944