Knee joint distraction: moving forward

Abstract

Knee joint distraction (KJD) is a joint-preserving technique for younger (<65 years) patients with knee osteoarthritis (OA). In joint distraction, the two bony ends of a joint are temporarily (6-9 weeks) placed at a certain distance (generally 5 mm), using an external fixation frame. KJD has been applied in several clinical trials and even in regular care conditions in a limited number of Dutch hospitals, focusing not only on symptom relieve but on cartilage regeneration as well. Although the exact working mechanism of the treatment is not yet clear, more and more details of the underlying processes are being revealed.

This thesis aims to take the next steps and move forward with KJD, in two directions. Part I focuses on clinical outcome and patient experience after KJD treatment, evaluated with a systematic review on KJD (chapter 2), the first long-term results (chapter 3), comparisons with alternative treatments from two randomized controlled trials (chapter 4), return to sport and work after treatment (chapter 5), clinical results in regular care (chapter 6), user-friendliness of a dedicated KJD device (chapter 7), pin tract infection reduction (chapter 8), and clinical and structural results one year after treatment with the dedicated device (chapter 9). Part II focuses on processes and potential working mechanisms occurring inside the joint as a result of KJD treatment, by evaluating current literature on clinical evidence and potential underlying mechanisms of KJD (chapter 10), different measurement methods for structural results on radiographs, CT and MRI (chapter 11 and 12), MRI cartilage thickness up to ten years after treatment (chapter 13) and after two years compared with high tibial osteotomy (chapter 14), cartilage quality using T2-mapping MRI (chapter 15), synovial fluid biomarker levels (chapter 16), osteophyte formation (chapter 17), and subchondral bone changes on CT (chapter 18).

Work in this thesis moves the field forward with clinical evaluation of KJD as a treatment for severe knee OA and improving understanding of the working mechanisms behind this treatment. KJD can bring long-lasting clinical efficacy and cartilage regeneration, and increasingly patient-friendly implementation in regular care is possible. KJD induces significant anabolic and catabolic changes in joint homeostasis, showing whole-joint modifications involving bone, cartilage, and synovial fluid, subsequently followed by overall repair. Future studies should focus on deepening comprehension of the mechanisms induced by KJD to improve patient selection, as well as using this unique population showing high rate structural and clinical response to improve understanding of different OA pathways in general.