Surgeon Variation in Perioperative Opioid Prescribing and Medium- or Long-term Opioid Utilization after Total Knee Arthroplasty: A Cross-sectional Analysis

Abstract

Background: Whether a particular surgeon's opioid prescribing behavior is associated with prolonged postoperative opioid use is unknown. This study tested the hypothesis that the patients of surgeons with a higher propensity to prescribe opioids are more likely to utilize opioids long-term postoperatively.

Methods: The study identified 612,378 Medicare fee-for-service patients undergoing total knee arthroplasty between January 1, 2011, and December 31, 2016. "High-intensity" surgeons were defined as those whose patients were, on average, in the upper quartile of opioid utilization in the immediate perioperative period (preoperative day 7 to postoperative day 7). The study then estimated whether patients of high-intensity surgeons had higher opioid utilization in the midterm (postoperative days 8 to 90) and long-term (postoperative days 91 to 365), utilizing an instrumental variable approach to minimize confounding from unobservable factors.

Results: In the final sample of 604,093 patients, the average age was 74 yr (SD 5), and there were 413,121 (68.4%) females. A total of 180,926 patients (30%) were treated by high-intensity surgeons. On average, patients receiving treatment from a high-intensity surgeon received 36.1 (SD 35.0) oral morphine equivalent (morphine milligram equivalents) per day during the immediate perioperative period compared to 17.3 morphine milligram equivalents (SD 23.1) per day for all other patients (+18.9 morphine milligram equivalents per day difference; 95% CI, 18.7 to 19.0; P < 0.001). After adjusting for confounders, receiving treatment from a high-intensity surgeon was associated with higher opioid utilization in the midterm opioid postoperative period (+2.4 morphine milligram equivalents per day difference; 95% CI, 1.7 to 3.2; P < 0.001 [11.4 morphine milligram equivalents per day vs. 9.0]) and lower opioid utilization in the long-term postoperative period (-1.0 morphine milligram equivalents per day difference; 95% CI, -1.4 to -0.6; P < 0.001 [2.8 morphine milligram equivalents per day vs. 3.8]). While statistically significant, these differences are clinically small.

Conclusions: Among Medicare fee-for-service patients undergoing total knee arthroplasty, surgeon-level variation in opioid utilization in the immediate perioperative period was associated with statistically significant but clinically insignificant differences in opioid utilization in the medium- and long-term postoperative periods.

Fig. 1.

Variation across surgeons in patients’ opioid utilization during the immediate perioperative period. Immediate perioperative period is defined as 7 days before surgery to 7 days after surgery. The overall surgeon fixed effects ranged from −25 to 76 morphine milligram equivalents (median fixed effect was set as 0), with different colors indicating P values at different significance levels relative to the median surgeon: orange, P < 0.01; blue, P < 0.05; gray, P < 0.1; and yellow, P ≥ 0.1.

Fig. 2.

Association between prescribing intensity in the immediate perioperative period and subsequent utilization in in the mid- and long-term postoperative periods. 95% CI calculated using standard errors that were adjusted for clustering at the hospital level. “Instrumental variable analysis” refers to an analysis that adjusted for all the patient characteristics listed in table 1 and that also used an instrumental variable approach, based on distance to the nearest high-intensity prescriber, to reduce confounding from unobservable patient and physician characteristics.