Professor University of Texas Medical Branch Galveston, United States
Background: Previous studies showed use of opioid after total knee replacement had no clinically meaningful improvement in post-operative pain. With the policy and guideline restricting opioid prescription, gabapentinoids (GABA) prescribing has substantially increased including for surgical conditions. However, the effectiveness of GABA is only well supported in treating neuropathic pain conditions, with no data on analgesia effectiveness of GABA use in the setting of surgery.
Objectives: To examine pain control associated with opioid and GABA among patients with elective knee replacement.
Methods: A 20% sample of Medicare enrollees aged 66+ receiving elective knee replacement in 2017-2019 was selected. We limited study cohort to those discharged to home, received home health care, and had both admission and discharge assessment of pain score by frequency of pain interfering with activities or movement at five levels. Study outcome was pain score reduction between admission and discharge. Opioid prescription after surgery was categorized as none and by low, medium and high dosages ( < 50, 50 to 89, or ≥ 90 MME per day). Receiving any GABA prescriptions after surgery and receiving any nerve block (sciatic, femoral, or bupivacaine) within 3 day of surgery was assessed. Other covariates included age, sex, race/ethnicity, original entitlement, dual Medicaid coverage, region, chronic pain diagnosis, and comorbidity. A multivariable linear regression model was built to examine pain reduction associated with opioid, GABA, and nerve block adjusting for covariates.
Results: Among 35,186 patients, 93% had an opioid prescription after surgery. Majority received low and medium dosage (35.1% and 38.5%). About 21.5% received GABA prescription and 55% had a nerve block. The average reduction of pain score was 1.76±1.01. Patients receiving medium or high dose of opioid prescription, or nerve black had higher admission pain. The admission pain score was similar between those with and without GABA prescription. In multivariable analyses, patients receiving medium and high dose opioid prescription had less pain reduction compared to those receiving low dose or no opioid prescription. Receiving GABA prescription was only significantly associated with pain reduction for those receiving low dosage of opioid. Receiving nerve block was associated with pain reduction. Results were similar for the outcome of having less daily pain at discharge; however, the effect of nerve block was marginally significant.
Conclusions: Our study showed no significant association between post-TKA opioid use and pain reduction. Co-prescribing GABA with low-dose opioid or receiving nerve block was associated with modest pain reduction. Further research is needed to identify alternatives to opioid use for post-operative TKA pain management.
