Mylène Jansen

MRI cartilage thickness up to ten years after KJD 265 13 This is the first time that the cartilage thickness changes after KJD treatment have been shown topographically and over such a long time span, and it seems that the most significant cartilage regeneration moves from the exterior side of the MAC initially to more interiorly long term. Short-term (2-year) subregional analyses in a different cohort have been performed after KJD before, and showed the most significant response on the exterior side of the MAC femur and tibia as well. 16 The exterior side of the MAC seems to be the most affected pre-treatment, meaning that perhaps the initial regenerative response takes place in the parts of the joint with thinner baseline cartilage and a slower response takes place in the less affected parts, including the LAC. In fact, baseline MAC cartilage thickness has previously been shown to significantly predict a short-term (2-year) cartilage thickness increase, as has Kellgren- Lawrence grade. 16 In the current study, Kellgren-Lawrence grade did not have a statistically significant influence. Fifteen of the 20 patients had Kellgren- Lawrence grade 3, so there were only very small groups for grade 1 (n=1), grade 2 (n=3) and grade 4 (n=1), hampering detection of statistically significant differences between the groups. Looking at the influence of Kellgren-Lawrence grade on the whole joint (Figure 3) a higher grade does seem to result in a higher 2-year MAC cartilage increase, but no strong conclusions can be drawn here because of the small sample size. In general, the baseline parameters showed opposing results for the 2- and 10-year change, indicating a distinction between a short- and long-term response, although in both cases the same beneficial effect. Performing short- and long-term MRI scans in a larger group of patients, ideally including for example biomarker analyses or MRI scans reflecting cartilage quality, could help drawing stronger conclusions on different responses between (types of) patients. This study had several limitations. First, the sample size of n=20 was small and there was no control group. Despite the small sample size, results are clear and consistent with previously published short-term results in similar patients. In the current study, long-term MRI cartilage thickness after KJD treatment was evaluated for the first time, adding unique evaluations and conclusions not previously known. Another limitation is that only cartilage thickness was evaluated, not cartilage quality. It would be interesting to see whether the newly generated cartilage is of the same quality, and if the quality of the already present cartilage changes. While dGEMRIC and T2-mapping scans were performed in a different cohort, these were up to 2 years only (T2-mapping analyses being performed currently). 21 Thirdly, patients are lost over time, mostly due to the (delayed) placement of a joint prosthesis. The last data available before TKA have been included and represent the potential worsening of the joint, which remains the reference after data imputation. This may have resulted in underestimation of the cartilage thickness over time. On the other hand, imputation of data based on data available of survivors may have led to overestimation of the repair activity over time, although none of the compartments showed a difference in cartilage thickness changes over the first 2 or 5 years between patients who did and did not complete ten years of follow-up (data not shown;