Mylène Jansen

CT subchondral bone changes after KJD 379 18 Introduction Knee osteoarthritis (OA) is characterized not only by cartilage degeneration, but by significant bone remodeling as well. 1 In end-stage knee OA, changes in the subchondral bone include subchondral (cortical) bone plate thickening and trabecular bone density decrease. 2,3 The overall bone shape changes as well, most notably by widening and flattening of femoral and tibial condyles and formation of osteophytes at the edges. 4 Bone changes after (joint-preserving) knee OA treatments are not evaluated often, as these studies generally focus on improving clinical patient-reported outcomes and, to a lesser degree, increasing cartilage thickness. Knee joint distraction (KJD) is 1 of the joint-preserving surgical treatments for relatively young (<65 years) knee OA patients. The treatment has been evaluated in several clinical trials, where it has shown significant short- and long-term clinical improvement. 5–8 Furthermore, KJD has demonstrated the ability to reverse OA cartilage degradation, as radiographic JSW and MRI cartilage thickness measurements showed significant short-term cartilage regeneration, which was sustained for up to 10 years after treatment. 6,9–11 Bone changes have been evaluated on plain radiographs, showing a decrease in overall subchondral bone density 1 year after treatment with increased osteophyte formation in the first 2 years after treatment. 9,12 However, bone changes after KJD have never been evaluated in 3-dimensions (3D), which enables measurement and visualization across the entire joint. As such, the purpose of this research was to explore subchondral cortical bone plate thickness, subchondral trabecular bone density, and overall bone shape from CT imaging before and up to 2 years after KJD treatment. Methods Patients Patients were included from 2 randomized controlled trials (RCTs). In 1 RCT, relatively young (<65 years) OA patients considered for total knee arthroplasty (TKA) were randomized to either KJD (n=20) or TKA (n=40) treatment. In a separate RCT, relatively young (<65 years) OA patients considered for high tibial osteotomy (HTO) were randomized to either KJD (n=23) or HTO (n=46). Inclusion and exclusion criteria were similar between the 2 trials, and included Kellgren-Lawrence grade >2 (as judged by orthopedic surgeon), no history of inflammatory or rheumatoid arthritis, no primary patellofemoral OA, leg axis deviation less than 10 degrees, and no surgical treatment of the involved knee <6 months ago. 6,13,14 In both RCTs, after randomization to KJD treatment, patients were asked to participate in an extended imaging protocol that included CT scans. The first 20 KJD patients (irrespective of the trial from which they were included) who gave written informed consent for the extended