Mylène Jansen

46 Chapter 3 Abstract Background: Knee joint distraction (KJD), a joint-preserving surgery for severe osteoarthritis (OA), provides clinical and structural improvement and postpones the need for total knee arthroplasty (TKA). This study evaluates 9-year treatment outcome and identifies characteristics predicting long-term treatment success. Methods: Patients with severe tibiofemoral OA (n=20; age <60 years) indicated for TKA were treated with KJD. Questionnaires, radiographs, and MRI were used for evaluation. Survival after treatment was analyzed, where ‘failure’ was defined by TKA over time. Results: Nine-year survival was 48%, and 72% for men (compared to 14% for women; p= 0.035) and 73% for those with a first-year minimum joint space width (JSW) increase of >0.5mm (compared to 0% for <0.05mm; p= 0.002). Survivors still reported clinical improvement compared to baseline (ΔWOMAC +29.9 points (95%CI 16.9–42.9; p= 0.001), ΔVAS -46.8mm (-31.6 to -61.9; p< 0.001)). Surprisingly, patients getting TKA years after KJD still reported clinical improvement although less pronounced (ΔWOMAC +20.5points (-1.8 to 42.8; p= 0.067), ΔVAS -25.4mm (-3.2 to -47.7; p= 0.030)). Survivors showed long- lasting minimum JSW increase (baseline 0.3mm (IQR 1.9), follow-up 1.3mm (2.5); p= 0.017) while ‘failures’ did not (baseline 0.4mm (1.8), follow-up 0.2mm (1.5); p= 0.161). First-year minimum JSW on radiographs and cartilage thickness increase on MRI predict 9-year survival (HR 0.05 and 0.12, respectively; both p< 0.026). Male sex was associated with survival (HR 0.24; p= 0.050). Conclusion: KJD shows long-lasting clinical and structural improvement. In addition to a greater survival rate for males (>two out of three), the initial cartilage repair activity appears to be important for long-term clinical success.