Comparative efficacy of intrathecal morphine and adductor canal block in the knee arthroplasty population: a retrospective multi-centre cohort study.

Background: Finding the balance of good postoperative analgesia while facilitiating mobility is important for a safe and satisfactory patient experience during Total Knee Arthroplasty (TKA). This study aimed to compare the efficacy of intrathecal morphine, adductor canal block, and their combination in optimizing pain management and postoperative recovery in TKA patients. This retrospective analysis of prospectively collected data evaluated postoperative pain scores, time to mobilisation, and length of hospital stay.
Methods: 1006 consecutive patients undergoing elective TKA across two large tertiary centres were included over six years. They were divided into one of four groups according to the type of analgesia received: Group N patients received no neuraxial morphine or regional block. Group B patients received adductor canal block (ACB) only. Group M patients received intrathecal morphine (ITM) but no regional block. Group BM patients received both ACB and ITM.
Results: Patients who received an ACB had faster postoperative mobilization compared to those without (p < 0.001). Patients in Group BM had the lowest pain scores at rest (Visual Analogue Scale (VAS) 2.9) and with movement (VAS 5.3), while Group B patients experienced the highest pain scores at rest (VAS 3.7) and on movement (VAS 6.5) (p = 0.005). Patients who received ITM had the lowest opioid requirements (p < 0.001). There was no significant differences between groups in requirement for rescue pain management strategies (p = 0.06).
Conclusions: The combination of ITM and ACB in patients undergoing TKA provides improved postoperative analgesia with lower postoperative opioid requirement and earlier mobilization compared with ACB or ITM alone.
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