Knee osteoarthritis (OA) affects millions of American adults and is characterized by substantial pain, joint stiffness, and functional limitations. Many patients with knee OA eventually undergo total knee arthroplasty (TKA), which can significantly increase mobility and decrease pain. However, the results of a new clinical trial suggest that preoperative opioid use may lead to worse pain outcomes following this procedure (Smith SR, et al. J Bone Joint Surg Am. 2017;99:803-808).
Savannah R. Smith, Clinical Research Coordinator, Orthopaedics and Arthritis Center for Outcomes Research, Department of Orthopaedic Surgery, Brigham and Women’s Hospital, Boston, MA, and colleagues gathered data from 156 patients who underwent TKAs at their institution between 2011 and 2013, and compared pain relief between those who used opioids before their surgery and those who had not. The average age of the patients was 66 years, and more than half (62.2%) of them were women.
The investigators collected patient-reported outcomes and demographic data from 6 weeks before and 6 months after surgery and obtained data regarding opioid use from the patients’ medical records. During the 2 years before surgery, 23% of patients had received ≥1 prescriptions for opioids, and 9% had used multiple opioids. After surgery, 96.2% of patients received ≥1 opioid prescriptions, and 93.6% received prescriptions for multiple opioids. The 2 most frequently prescribed opioids were oxycodone (96.2%) and hydrocodone (33.3%).
Using standard pain scales (eg, Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC] and Pain Catastrophizing Scale), Ms Smith and colleagues analyzed the pain experiences of patients undergoing total knee replacement surgery by comparing the changes in pain scores 6 months after surgery between patients who had used opioids before TKA and those who had not. The analysis included a propensity score to account for other factors associated with an increased likelihood of patients using opioids.
Ms. Smith and colleagues found that opioid use before surgery resulted in decreased pain reduction after surgery. In particular, patients who had not taken opioids before their knee replacement surgery had a mean 6-month WOMAC pain score of 10.5 points (95% confidence interval [CI], 8.3-12.8) compared with 17.1 points (95% CI, 12.8-21.4) for those who had taken these medications.
“Preoperatively, there was a small but not significant difference in the WOMAC pain scores between the groups, whereas the pain scores at 6 months were significantly worse for those who had used opioids preoperatively (p = 0.008). This difference indicates that preoperative opioid use may have affected the pain reduction achieved with the TKA,” Ms. Smith and colleagues asserted.
In addition, patients who used opioids before surgery had a mean Pain Catastrophizing Scale score of 15.5 points, whereas those who had not used opioids had a score of 10.7 points.
“As individuals with osteoarthritis spend an average of 13 years between trials of nonoperative therapies and elective TKA, our results should be viewed as a warning that opioid use may be problematic during this period due to their negative effects on subsequent TKA outcomes,” the investigators concluded.