Effect of periarticular morphine injection for total hip arthroplasty: a randomised, double-blind trial

100 patients scheduled for unilateral total hip arthroplasty (THA) were randomized to receive analgesic peri-articular cocktail injection containing ropivacaine, epinephrine, ketoprofen, methylprednisolone sodium, and normal saline, with or without the addition of morphine. The primary outcomes of interest were pain at rest and during motion, measured on a Visual Analog Scale (VAS). Secondary outcomes of interest included nausea on a numeric rating scale (NRS), the number of vomiting cases per person, anti-emetic drug consumption, levels of hemoglobin and C-reactive protein (CRP), range of motion in flexion and abduction, thigh swelling, the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and the incidence of complications. Results revealed no significant differences in VAS pain scores, both at rest and during movement, between the morphine and control groups. NRS nausea scores in the first hour post-operation, as well as total metoclopramide consumption, was significantly higher in the morphine group. No significant differences were observed between the two groups in total rescue analgesia consumption, levels of hemoglobin and CRP, WOMAC index scores, range of motion in flexion or abduction, thigh swelling, or the incidence of complications.