Postoperative Painful Chronicization After Knee Replacement Surgery : Exploratory Study of BDNF's Kinetics

Chronic pain is an extremely disabling disease. It is a major public health problem due to the lack of effective therapy. Chronic postoperative pain (CPOP) is defined by a painful symptomatology in the operated area unrelated to previous pain, present for more than 3 months, and without any link to surgical complication. The prevalence of chronicization of postoperative pain is 30% after total knee arthroplasty. Identification of clinical, biological and psychological profiles are crucial to prevent CPOP. A biologic factor, Brain Derived Neurotrophic Factor (BDNF) produced by a variety of cells is a key regulator of neuroplasticity. BDNF is increasingly studied in the mechanisms of cerebral sensitization and pain chronicization. The role of BDNF in pain of patients remains to be explored in a prospective study. The aim of this observational study is to compare the kinetics of BDNF after total knee arthroplasty in patients with and without CPOP. Patients will be included in the study at the preanesthetic consultation. Serum BDNF levels will be measured preoperatively, 48h postoperatively, 3 and 6 months after surgery.