Mylène Jansen

262 Chapter 13 As for the whole-joint analyses, cartilage thickness of the 4 compartments showed a biphasic response after treatment: an initial cartilage prompt regeneration phase up to 2 years, statistically significant for MAC femur (baseline 1.3 (SD 0.3) – 2 years 1.6 (0.4); p= 0.010) and MAC tibia (1.7 (0.3) – 1.9 (0.3); p= 0.016), and a gradual degeneration phase between 2 and 10 years, statistically significant for MAC tibia (ten years 1.8 (0.3); p= 0.044) but not the MAC femur (ten years 1.4 (0.3); p= 0.072). The LAC femur (2.1 (0.4) – 2.2 (0.4); p= 0.343) and LAC tibia (2.2 (0.3) – (2.4 (0.3); p= 0.058) showed the same trend of an increase in the first 2 years, with some more variation in the years afterwards (both p> 0.1). Since the MAC compartments clearly show lower cartilage thickness values even at baseline, Supplementary Figure S3 displays the compartmental cartilage thickness over time using separate Y-axis ranges for the subfigures, to better visualize the changes that occur in each compartment. The mean and 95% confidence interval (95%CI) of all data points are shown in Supplementary Table S1. Because this analysis was performed with imputed data, a sensitivity analysis was performed only including the 8 patients with full data sets. Results are shown in Supplementary Figure S4, showing the same biphasic response. Influence of baseline parameters The influence of baseline parameters on the whole-joint 2- and 10-year changes are shown in Figure 4 for all patients with a medial MAC. Over the short-term (2 years), a higher age, lower BMI, male sex and a higher Kellgren-Lawrence grade seemed to result in a higher medial cartilage thickness increase. It should be noted 75% of patients had Kellgren-Lawrence grade 3, however, so these results are based on only a very small number of patients. Long-term results (ten years) generally showed the opposite, although for sex and Kellgren-Lawrence grade it is important to note that at 10 years only 1 female patient was left with grade 2 and 6 male patients all with grade 3. None of the results were statistically significant, although especially male sex and higher Kellgren-Lawrence grade seemed to have some positive influence on the 2-year change in the medial compartment. Influence on clinical outcome The influence of the compartmental cartilage thickness changes over time on the change in total WOMAC is shown in Table 2. As indicated, the 2-year cartilage thickness change did not have a significant influence on the 2-year change in total WOMAC for any of the compartments. However, the 10-year LAC tibia thickness change had a statistically significant influence on the 10-year total WOMAC change (p=0.031) with a relatively large effect estimate: 1 mm cartilage thickness increase could result in 24 points of total WOMAC increase. Looking at the WOMAC subscales separately, the 10-year LAC tibia thickness increase had a significant influence only on the WOMAC function scale (p=0.030; effect estimate 24.93 (95%CI 2.57–47.30)) but not on the other subscales (both p>0.05), although effect estimates were still relatively large (both >17.09).