Medial Unicompartmental Knee Arthroplasty Is Associated With Significant Reduction in Pain and Opioid Prescribing Patterns Compared to Total Knee Arthroplasty: A Retrospective Cohort Study of 9595 Knees

Background Total knee arthroplasty (TKA) and medial unicompartmental knee arthroplasty (mUKA) are successful operations to treat knee osteoarthritis. While mUKA is associated with less postoperative pain, there is a paucity of literature exploring postoperative opioid consumption and prescribing patterns between these procedures. The objective of this study was to evaluate in-hospital opioid consumption and postoperative opioid prescribing patterns, in milligram morphine equivalents (MMEs), between patients undergoing primary unilateral mUKA vs TKA. Methods A single-institution retrospective review of patients undergoing primary mUKA or TKA from 2019 to 2022 was performed. Patients were excluded if they lacked 90-day follow-up, used narcotics preoperatively, had a history of anxiety/depression, or underwent additional procedures within 90 days. Multivariable regression analysis assessed inpatient MME consumption, as well as discharge +90-day total MME prescribing patterns. Results A total of 9595 patients were analyzed (720 mUKA; 8875 TKA). The mUKA cohort had an adjusted length of stay 25.4 hours shorter than the TKA cohort ( P < .001). The mUKA cohort was associated with consuming 0.17 MMEs/hour fewer while inpatient ( P = .005). Regression analysis found mUKA to be associated with 275.4 fewer MMEs in the first 90 days ( P < .001) when combining discharge plus 90-day refill MMEs. Conclusions In this large contemporary series, mUKA was associated with significantly shorter length of stay, statistically significant but clinically similar hourly inpatient MME consumption, and decreased 90-day MME prescribing patterns compared to TKA. These findings highlight favorable perioperative opioid and resource utilization associated with mUKA within its established indications and may contribute to patient counseling regarding expected postoperative recovery.