Periarticular injection versus placebo in total knee arthroplasty with intrathecal morphine

Abstract

Introduction

Periarticular injection (PAI) is one part of total knee arthroplasty (TKA) multimodal analgesia protocols. PAI combined with neuraxial anesthesia including intrathecal morphine (ITM) has not been previously investigated. This study prospectively compares PAI to placebo injection in patients undergoing TKA under spinal anesthesia with ITM.

Methods

We performed a prospective, double-blinded randomized controlled trial comparing immediate postoperative outcomes after TKA. All patients received combined spinal-epidural (CSE) anesthesia with ITM and multimodal analgesia. The study group received a standardized PAI with 0.5% ropivacaine, clonidine, ketorolac, and epinephrine, while the control group received PAI with saline. Exclusion criteria were revision surgery, inability to receive epidural anesthesia or PAI, patients taking greater than 80 morphine milligram equivalents (MME) daily prior to surgery, and lack of patient consent to participate in the study.

Results

Sixty-four patients enrolled and completed the study from 2015 to 2021. Thirty-four were randomized to the study group and 30 to the control. There was no difference in mean total postoperative opioid consumption between PAI (125.49 MME) and control (138.80 MME); (p = 0.556). There was also no difference in opioid requirements at 0–24 and 24–48 h between PAI (58.87 and 70.57 MME), and control (70.57 and 69.72 MME); (p = 0.308 and p = 0.556).

Conclusion

This study, while underpowered, demonstrates that PAI does not significantly decrease opioid consumption after TKA compared to placebo injection when utilizing ITM spinal anesthesia. When ITM is used, PAI may be reasonably be excluded from the protocol without affecting opioid requirements.