Mylène Jansen

KIDA performance in severe OA 215 11 Introduction Osteoarthritis (OA) is a degenerative joint disease characterized by structural changes such as cartilage degeneration, osteophyte formation, and subchondral bone changes. 1 In knee OA, these characteristics are usually evaluated on radiographs, frequently taken in weight-bearing position and in anterior-posterior or posterior-anterior (PA) direction. 2 Although the use of imaging techniques such as magnetic resonance imaging (MRI) is increasing, radiography remains the primary technique for the diagnosis and monitoring of knee OA. With the exception of joint space width (JSW) as a measure of cartilage thickness, radiography based knee OA characteristics are most often evaluated using a grading system, such as the Kellgren & Lawrence (KL) grade and the Altman score. 3,4 While these grading systems have been validated and proven useful, stepwise scoring of OA-related parameters makes results less sensitive to small changes over time. This was 1 of the main motivations for the development of the Knee Images Digital Analysis (KIDA) software in 2008. 5 Using KIDA, the individual radiographic knee OA features of JSW, subchondral bone density, osteophytes, tibial eminence height, and knee joint angle can be measured objectively and quantitatively resulting in continuous variables. The usefulness and validity of the KIDA parameters was initially demonstrated for patients with relatively mild knee OA, as indicated by their average KL grade of 1.3, and measurements were shown to distinguish these patients from healthy controls. Indeed, such distinction in mild OA is key for early detection of presence and progression of radiographic changes. Both the inter- and intra-observer variability were proven to be relatively low, and the smallest detectable difference (SDD) for the different parameters showed good results as well. 5 Since then, KIDA has been used in observational cohorts with patients with relatively mild knee OA, such as the CHECK and APPROACH cohorts. 6,7 However, KIDA parameters have also been used as endpoints in studies including patients with significantly more severe OA. End-stage OA patients treated with knee joint distraction (KJD) or high tibial osteotomy (HTO) were evaluated with KIDA before and up to 9 years after treatment. 8–11 For these severe knee OA cases KIDA has not been evaluated. The goal of the present study was to evaluate the performance of KIDA in patients with severe knee OA. Methods Patients Patients were included from 3 different clinical studies. Twenty (20) patients with end-stage knee OA, in regular care indicated for total knee arthroplasty (TKA) and relatively young (age <60 years), were included in an open prospective study and treated with KJD. In a randomized controlled trial (RCT), where KJD was compared with TKA, 20 end-stage knee OA patients indicated for TKA were treated with KJD. In a separate RCT, KJD was compared with HTO, and another 22 and 45 patients indicated for HTO were treated with KJD or HTO,