Which patient-specific and surgical characteristics influence postoperative pain after THA in a fast-track setting?

BACKGROUND In our hospital a fast-track setting including a multimodal pain protocol is used for total hip arthroplasty (THA). Despite this multimodal pain protocol there is still a large range in reported postoperative pain between patients, which hinders mobilization and rehabilitation postoperatively. The goal of this study was to identify which patient-specific and surgical characteristics influence postoperative pain after THA in a fast-track setting. METHODS All 74 patients with osteoarthritis of the hip who underwent primary THA procedure by anterior supine intermuscular approach between November 2012 and January 2014 were included in this prospective cohort study. The protocol for pain medication was standardized. Postoperative pain determined with the Numeric Rating Score was collected at 17 standardized moments. Linear mixed models were used to examine potential patient-specific and surgical factors associated with increased postoperative pain. RESULTS Pain patterns differed substantially across individuals. Adjusted for other variables in the model, preoperative use of pain medication (regression coefficient 0.78 (95% CI 0.28-1.26); p = 0.005) and preoperative neuropathic pain scored by DN4 (regression coefficient 0.68 (95% CI 0.15-1.20); p = 0.02) were the only factors significantly associated with higher postoperative pain scores. CONCLUSIONS The knowledge of which factors are associated with higher postoperative pain scores after THA in a fast-track setting may help optimizing perioperative postoperative pain management and preoperative education of these patients. TRIAL REGISTRATION The study was retrospectively registered in the ISRCTN registry under identifier ISRCTN15422220 (date of registration: July 25, 2017).