Effect and safety of intravenous versus oral acetaminophen after unicompartmental knee replacement

Abstract Background: Due to the soft tissue injury and large amount of bone destruction involved, undesirable postoperative pain remains a challenge for both patients and surgeons after unicompartmental knee replacement (UKR). However, there are no studies comparing the effectiveness of oral and intravenous acetaminophen as part of a standard multimodal perioperative pain regimen after UKR. Thus, this prospective randomized study was conducted to compare pain control outcomes with postoperative oral versus intravenous acetaminophen use in adults undergoing UKR. Methods: The institutional review board of the Traditional Chinese Medicine- western Medicine Hospital of Cangzhou approved the study protocol. This blinded and randomized study was carried out in accordance with the principles of the Helsinki Declaration. We included patients who were scheduled for UKR with an American Society of Anesthesiologists status of I to III, who were mentally competent, and who were able to give consent for enrolment in the study. Patients were randomly assigned on a 1:1 basis to receive either intravenous acetaminophen or oral acetaminophen. We ensured that the patients, care providers, and outcome assessors were blinded to the group assignment during the study period. Primary outcomes were postoperative pain at rest and during motion (knee flexion of 45°) measured using a visual analog scale score. Secondary outcomes included morphine consumption at 24, 48, and 72 hours after surgery, length of hospital stay, range of motion, daily ambulation distance, and adverse events occurrence. All statistical analyses were performed using SPSS 25.0. Differences associated with a P value of <.05 were considered statistically significant. Results: It was hypothesized that patients receiving intravenous acetaminophen would exhibit similar postoperative outcomes compared with patients receiving oral acetaminophen. Trial registration: This study was registered in Research Registry (researchregistry5825).