Mylène Jansen

62 Chapter 4 (SD) 16.7) was deemed clinically relevant. 14 A 5% type I error and power of 80% were used, with a 15% margin allowed for loss to follow-up. The trial was granted ethical approval (No 10/359/E) and was registered in the Netherlands National Trial Register (NTR2809). In a separate RCT conducted between 2011 and 2013 at 2 centers (Maartenskliniek Woerden and University Medical Center Utrecht), patients with medial compartmental knee OA considered for HTO and less than 10° varus were randomized 2:1 to either HTO (n=46) or to KJD (n=23; KJD HTO ) treatment. Randomization was done in the same way as the TKA trial. The original sample size calculation was based on the change in percentage of denuded bone area as evaluated by quantitative MRI. The group sizes calculated however were sufficiently large to evaluate clinical outcome based on WOMAC score (15 points difference, with a 5% type I error and a power of 80%), all based on non-inferiority as described above. MRI data are not available yet and because of the combination of both independent trials in 1 manuscript, it was chosen to use WOMAC as primary outcome for both studies. The trial was granted ethical approval (No 11/072) and was registered in the Netherlands National Trial Register (NTR2900). Table 1 : In- and exclusion criteria of the 2 randomized controlled trials Both KJD vs TKA and KJD vs HTO KJD vs TKA only KJD vs HTO only Inclusion criteria • Age <65 years • Radiological joint damage: Kellgren & Lawrence score above 2 (as indicated by orthopedic specialist) • Intact knee ligaments • Normal range-of-motion (min. of 120° flexion) • Normal stability • Body Mass Index <35. • Patients considered for TKA according to regular clinical practice • Patients with medial tibiofemoral compart- mental OA considered for HTO according to regular clinical practice Exclusion criteria • Psychological inabilities or difficult to instruct • Not able to undergo MRI examination (stan- dard protocol) • Inflammatory or rheumatoid arthritis present or in history • Post-traumatic fibrosis due to fracture of the tibial plateau • Bone-to-bone contact in the joint (absence of any joint space on radiograph); • Surgical treatment of the involved knee <6 months ago • Primary patellofemoral OA • An infectious sus- ceptible prosthesis (joint replacement) in situ • Mechanic varus axis-de- viation of more than 10 degrees • Contralateral knee OA that needs treatment HTO: high tibial osteotomy; KJD: knee joint distraction; TKA: total knee arthroplasty.