Mylène Jansen

MRI cartilage thickness after KJD and HTO 277 14 Introduction Knee osteoarthritis (OA) is the most prevalent form of OA and 1 of the most common causes of disability worldwide. 1 It poses a major global burden, anticipated to increase in the future. 2,3 End-stage knee OA is frequently treated with total knee arthroplasty (TKA), a generally effective and safe treatment. 4,5 However, in younger and more active patients it involves a risk of failure, and future revision surgery. In these cases a joint-preserving alternative may be a desired option. 6 In case of predominantly unicompartmental knee OA, unicompartmental knee arthroplasty (UKA), high tibial osteotomy (HTO), and knee joint distraction (KJD) may be considered as (partly) joint-preserving treatment options. 7–11 As opposed to UKA, only HTO and KJD fully preserve the native joint tissue. HTO permanently unloads the more affected compartment (MAC) of the tibiofemoral joint by (over-) correcting the leg axis. This puts more load on the less affected compartment (LAC), and has shown good long-term survival. 12,13 Further, HTO treatment has shown an increase in radiographic joint space width (JSW) and, in some cases, even cartilage restoration. 14–16 Yet, comparison of JSW before and after HTO may be unreliable, as pseudo-widening of the unloaded compartment may occur due to the induced change in leg axis. Therefore, a direct measurement of cartilage structure is required to evaluate whether HTO has indeed a positive effect on maintenance of cartilage tissue. KJD has been used for uni- and bicompartmental knee OA. KJD aims to promote cartilage restoration by temporarily unloading both compartments, using an external fixation frame. Also KJD has shown good long-term survival and both radiographic JSW increase and cartilage thickness restoration by MRI. 14,17–24 In a previous randomized controlled trial (RCT) that compared HTO with KJD, the clinical effects (based on patient-reported outcomes) and structural effects (based on radiographic measurements) of KJD and HTO were shown to be similar in patients indicated for HTO with an leg axis deviation of <10°. 14,21,22 However, for the reasons provided above, direct cartilage thickness measurements need to be compared between KJD and HTO in order to accurately evaluate the efficacy of both treatment options on cartilage structure. The main goal of this study therefore was to compare 2-year changes in MRI cartilage thickness and denuded joint surface areas during treatment with KJD versus HTO. We hypothesized that KJD is more effective in restoring cartilage in the MAC, while avoiding negative effects (more cartilage thinning) on the LAC. The secondary goal was to identify (baseline) factors that can predict cartilage restoration activity as measured on MRI, in order to help select the appropriate patients for that type of therapy.