Mylène Jansen

Summary and general discussion 403 19 has moved the field on KJD forward, but additional steps forward could and should be made. Moving forward with KJD as a successful treatment for severe knee OA means focusing on providing the clinical outcome that patients desire, not just on a group level but also on an individual patient level. It is clear from the research presented throughout part I that KJD is able to give patients relief of symptoms such as pain and stiffness, even for the long-term ( chapter 3 ) and outside of trial conditions ( chapter 6 ). KJD can even improve quality of life ( chapter 4 and chapter 9 ) especially with respect to physical problems. Despite many positive results, it is important to realize that KJD treatment is not the holy grail in treating knee OA. The ability to postpone TKA for at least 10 years in half of the patients that were originally indicated for it is impressive ( chapter 3 and chapter 13 ), but at the same time, there are also patients who within the first 2 years after treatment already choose additional surgical treatment ( chapter 4 ). There is a contrast between individual patients in this regard that is not easily explained, probably partly because of the subjectivity involved in deciding to undergo additional surgery. Supporting this subjectivity is that KJD patients chose to have TKA surgery despite, on group level, still clearly experiencing the beneficial effects of KJD surgery ( chapter 3 ). The decision-making in opting for TKA has been studied previously, showing that patients are heavily influenced by not only their own expectations and fears, but also by their close social environment and healthcare provider. 19,20 This results in an individual effect that is not easily measurable, and might influence any other surgical treatment as well including (follow- up) TKA surgery. Still, there are some indications that there are physiological differences between patients who do and do not respond well. Male patients show better response to distraction of not only the knee ( chapter 3 and chapter 13 ), but also the ankle and hip. 21,22 Patients with more severely affected joints show a better clinical ( chapter 3 ) and cartilage restoration ( chapter 13 and chapter 14 ) response to KJD as well. 23 This suggests clinical treatment response is not solely subjective, but at least party dependent on underlying systemic and joint-specific characteristics. It can also be debated whether patients choosing TKA surgery a few years after KJD should be interpreted as treatment failure. The goal of KJD is ultimately to postpone TKA surgery long enough that a revision surgery later in life can be prevented (see Figure 1). The lifetime risk of revision is higher in younger patients, especially under the age of 65, and in these patients even postponing a TKA with 5 years could decrease the risk of revision with up to 20 percentage points. 24 Indeed, recent data from the Dutch Arthroplasty Register showed delaying TKA placement by 5 years in patients under the age of 75 could avoid 17% of revisions. 25 Furthermore, a first KJD treatment does not necessarily have to be followed by TKA or even a UKA. Treating patients with KJD for a second time years after the first treatment has never been tried. A successful second ankle distraction was anecdotally reported, so it is not unlikely that a second KJD could lead to additional years of positive outcome as well. There are also patients who have been treated with HTO years after KJD, or with