Mylène Jansen

Long-term clinical success of KJD 55 3 no statistically significant difference in WOMAC scores. Considering a minimally clinical important difference of 15–20 points for the total WOMAC and 25–30 mm for VAS pain, numbers that have been reported as clinically relevant differences in other studies 13,14 , there was no clinical difference between survivors or failures either. As clinical scores are still improved compared to baseline at the moment of choosing TKA after KJD, it could be questioned whether TKA is a valid end-point for survival. Additional reasons may have lead these patients to choose for a subsequent TKA. The average time to TKA for failures was 6.4 years, and the potentially temporary decrease in clinical benefit seen around 5 years post-treatment (Figure 2) might be causative to choose a subsequent TKA. Anecdotally knee OA patients treated with distraction are willing to undergo a second KJD years after the first KJD which has for ankle distraction been proven to be successful again. The minimum and mean JSW of the MAC at baseline were not different for survivors and patients who underwent TKA, where survivors showed a larger JSW increase in the first year. The gradual decrease that was subsequently observed seemed parallel for the 2 groups, suggesting that the initial JSW gain is crucial as it is this increase that is largely maintained during the remainder of follow-up. Despite the smaller initial JSW increase in patients who underwent TKA after KJD, their JSW was on average not decreased compared to baseline at the last measurement before TKA. This should be considered in the context of a general decrease in JSW over time as natural course of joint degeneration in case the disease remains untreated. 7 Regression analysis showed several factors predicting 9-year survival of KJD treatment. In the present study, for the first time it is shown that structural improvement in the first year after distraction predicts long-term clinical survival. Chance for survival is better after a higher initial minimum JSW increase and increase in mean cartilage thickness on MRI when corrected for baseline values. Also men had a better chance for survival, as described previously for hip and ankle distraction as well. 15,16 It was observed that male patients generally had a larger initial increase in minimum JSW (>0.5 mm increase: 9 males, 2 females; <0.5 mm increase: 1 male, 5 females), but performing a Cox regression analysis with both sex and 1-year change in minimum JSW as covariates showed this barely affected the HR (0.29 uncorrected for baseline), indicating that the minimum JSW increase has a strong association with survival even when corrected for sex. Pin-tract infections during treatment, which occurred in 17 of the 20 patients, were not predictive of survival ( p= 0.578). The previously reported decrease in knee flexion angle at 3 and 6 months also was not predictive ( p= 0.776 and p= 0.698, respectively). 7 A clear limitation of the present study is the small number of patients. However, this is thus