The prognostic value of dGEMRIC regarding future knee OA Long-term assessment after traumatic chondral injury and ACL injury

Sammanfattning: Abstract Background: Osteoarthritis (OA) is the most common joint disorder globally and a major cause of disabiltiy with the knee joint responsible for 80% of the disease burden. Progressive degenerative changes in cartilage tissue result in deterioration and loss of articular cartilage. Cartilage has poor capacity of healing and the detection of degeneration usually occurs at a stage of progression where changes are irreversible. To improve the understanding of the degenerative process and to monitor early stage cartilage disease, new methods are needed. Delayed gadolinium enhanced magnetic resonance imaging of cartilage (dGEMRIC) is a technique to evaluate cartilage quality by estimation of glycosaminoglycan (GAG) content, a low dGEMRIC index indicates low cartilage quality. The characteristic resistance to compressive forces of healthy cartilage relies on high GAG content. Decreasing GAG content is regarded as one of the first alterations in progression to cartilage degeneration. Aims and cohorts: 1) To validate the dGEMRIC measurement technique. 2) To monitor changes in cartilage quality in two cohorts of knee-injured patients: a) traumatic cartilage injury and b) ACL injury. To investigate the capacity of dGEMRIC to predict clinical and radiographic OA in both these cohorts. Results: For 6 investigators, the inter- and intra-observer reproducibility of dGEMRIC measurements with manual definition of different regions of interest was good with CV% of <3% at repeated measures. No difference was found related to investigator experience. A traumatic cartilage injury was associated with a high prevalence of OA after 17 years. The dGEMRIC index in the repair tissue was low already 2 years postoperatively, indicating fibrocartilage of low quality. A negative correlation between the dGEMRIC index in the adjacent cartilage and future OA suggests that the quality of the surrounding cartilage influences outcome after cartilage repair surgery. 29 patients with ACL rupture were investigated with dGEMRIC 3 weeks and 2 years after injury. dGEMRIC index was lower compared to non-injured controls. Patient that had sustained meniscectomy, or had BMI ≥25, had lower cartilage quality at 2 years. Long-term follow-up was performed in 16 patients with cartilage repair surgery and 31 patients with ACL rupture. In the cartilage repair group, the 12 knees that had developed radiographic OA had lower dGEMRIC index (p=0.07), and in the ACL group low medial dGEMRIC index was associated with both medial ROA and OA symptoms (p<0.05) after 14 years. Conclusion: Non-invasive assessment of cartilage quality with dGEMRIC is feasible and measures relevant differences in a clinical context. Cartilage quality assessed with dGEMRIC has a prognostic capacity relative knee OA development.