Predicting outcome of total knee replacement surgery in patients with knee osteoarthritis: a prospective study on the role of phenoptypic characteristics related to osteoarthritis.

Even though a Total Knee Replacement (TKR) is an effective surgical treatment for end-stage knee osteoarthritis (KOA) and the majority of patients report substantial pain relief and functional improvement following this surgical procedure, literature shows that 20-40% of patients are dissatisfied with the postsurgical outcome.Given the high costs related to TKR surgery and the substantial number of patients who do not meet the level of improvement after surgery, the decision to implant a TKR should be very well-considered. It is crucial to improve our understanding of the mechanisms contributing to persisting pain and disability following TKR.There is growing body of research suggesting that in a subgroup of patients with KOA the clinical picture is dominated by sensitization of central nervous system pain pathways (i.e. central sensitization) rather than by structural dysfunctions causing nociceptive pain. Briefly, this means that the pain is to a considerable degree due to hypersensitivity of the central nervous system, rather than being just caused by structural joint damage.Therefore, with our current ongoing study (funded BOF-DOCPRO4 project initiated November 1st 2017) we aim to understand the role of central pain processing in addition to structural and functional impairments related to KOA to predict unsatisfactory outcome (in terms of pain, symptoms, physical performance and QOL) after a TKR in patients with KOA. However, within the context of recent research developments in OA and recent suggestions proposed in international literature, we would like to upgrade our current research project and add a few measurements. In very recent systematic reviews, several OA phenotypes have been proposed, which are in part in line with the aims of our current ongoing study. However, we additionally want to investigate to what extent metabolic and inflammatory factors are related to the clinical expression of OA and are contributing to prognosis and treatment response. Moreover, in literature, different phenotypes are hypothesised and it is also plausible that the proposed phenotypes are not complete distinct entities and that interactions may exist.Therefore, we want to upgrade our research study and add some measurements to investigate the role of different OA characteristics, namely structural joint damage, inflammatory and metabolic factors and pain processing factors, in the clinical expression of KOA before and after a TKR. Moreover, we aim to unravel the interrelationship between these factors and to determine different phenotypes in relation to the outcome and prognosis after TKR, since these phenotypes may be particularly important for tailored treatment. In order to reach these objectives, a longitudinal prospective study will be performed, with specific data collection presurgical (T0) and 6 months (T1) and 1 year (T2) postsurgical.The strength of our current research study (including the proposal to upgrade the project and to add measurements) is that we will examine all putative prognostic factors on the basis of the biopsychosocial model. Besides several psychological factors (cognitive emotional modulation), we assess biomechanical factors (i.e. structural impairments, such as radiographic severity of OA, and functional impairments such as muscle weakness and proprioceptive deficits) and metabolic and inflammatory factors, and examine the role of altered central pain processing. We want to define OA phenotypes that are easy interpretable and possibly related to the outcome and prognosis after TKR.

Keywords:PHENOTYPE, OSTEOARTHRITIS, TOTAL KNEE REPLACEMENT, CHRONIC PAIN

Disciplines:Orthopaedics, Human movement and sports sciences, Rehabilitation sciences