Predicting outcome after total knee replacement surgery in patients with knee osteoarthritis: a prospective study on the role of altered central pain processing in addition to structural and functional impairments related to knee 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. Similar to other chronic pain conditions, 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, it is not surprising that surgical interventions such as TKRs do not guarantee pain reduction and functional recovery, as the pain goes beyond the joint. 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 and it emphasizes the need for further research on the role of altered central pain processing in patients with end stage KOA awaiting TKR surgery.This research proposal has two main objectives:1) to unravel to which extent central pain processing and structural and functional impairments contribute to the clinical expression of KOA (pain, symptoms, physical performance and quality of life) in patients with end-stage KOA before (at baseline) and 6 months after primary TKR surgery. 2) to unravel which factors are predictive for an unsatisfactory outcome (in terms of pain, symptoms, physical performance and quality of life) 6 months and 1 year after a primary TKR. 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.This study allows identification of prognostic factors for unsatisfactory outcome in KOA patients after a primary TKR. Previous longitudinal studies investigating predictors of poor outcome after TKR, mainly focused on structural and functional factors related to the knee joint, while central pain processing was left unnoticed. Other studies mainly focused on psychological factors as potential predictors of poor outcome. The strength of the recent proposal 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 examine the role of altered central pain processing measured in four ways (Pressure Pain Thresholds, Conditioned Pain Modulation, tactile acuity, Central Sensitization Inventory questionnaire). In this study, it is hypothesized that in patients with altered central pain processing an unsatisfactory effect of TKR surgery on KOA pain, symptoms, physical performance and quality of life can be expected, as there is no clear relation between peripheral input and perceived pain. It is possible that in this subgroup interventions aiming to desensitize the central nervous system might be more beneficial.In future interventional research, it can be clarified whether new interventions, such as cognitive-behavioral therapy or therapeutic pain neuroscience education, whether or not in combination with surgery, are useful. These new interventions target different aspects such as the central nervous system in contrast to therapeutic modalities that are only directed to structural knee joint pathology.

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

Disciplines:Rehabilitation sciences