A Randomized, Double-blind, Placebo-controlled Trial on the Prevention of Chronic Postoperative Pain after Inguinal Hernia and Knee Surgery by Postoperative Treatment with Tapentadol.

INTERVENTION: Trade Name: Tapentadol Product Name: Tapentadol Pharmaceutical Form: Tablet Pharmaceutical form of the placebo: Tablet Route of administration of the placebo: Oral use CONDITION: Chronic pain after inguinal hernia surgery and knee replacement surgery. Therapeutic area: Analytical, Diagnostic and Therapeutic Techniques and Equipment [E] ‐ Anesthesia and Analgesia [E03] PRIMARY OUTCOME: Main Objective: To prevent the development of chronic postoperative pain after inguinal hernia surgery and knee replacement surgery and to to further explore the mechanism behind the development of chronic postoperative pain. Primary end point(s): (1) The effect of tapentadol compared to placebo on the development of chronic pain in the first year after surgery; Secondary Objective: To explore the relationship between the pre‐operative presence of CPM and central sensitisation in pre‐operative pain free patients (inguinal hernia surgery) and in patients with chronic pain pre‐operatively (osteoarthritis patients planned for knee replacement surgery) on the development of chronic postoperative pain. Timepoint(s) of evaluation of this end point: 3, 6 and 12 months after surgery. SECONDARY OUTCOME: Secondary end point(s): (1) The influence of the pre‐operative pain profile on the development of chronic postoperative pain;; (2) The influence of tapentadol and placebo on the individual pain profiles and its influence on the development of chronic postoperative pain. Timepoint(s) of evaluation of this end point: 1, 3, 6 and 12 months after surgery. INCLUSION CRITERIA: 1. Patients scheduled for elective inguinal hernia surgery or knee replacement surgery (to assess the severity of the knee osteoarthritis the Kellgren and Lawrance criteria will be used; see appendix 1). 2. American Society of Anesthesiologists score 1, 2 or 3 3. Age between 18‐80 years Are the trial subjects under 18? no Number of subjects for this age range: F.1.2 Adults (18‐64 years) yes F.1.2.1 Number of subjects for this age range 400 F.1.3 Elderly (>=65 years) yes F.1.3.1 Number of subjects for this age range 140