Many patients undergoing hip or knee replacement are still taking prescription opioid pain medications up to 6 months after surgery, according to a study published in the journal PAIN.
Jenna Goesling, PhD, University of Michigan, Ann Arbor, Michigan, and colleagues identified several “red flags” for persistent opioid use — particularly previous use of high-dose opioids.
The results suggest that some patients continue to use these potentially addictive pain medications despite improvement in their hip or knee pain.
Total knee and hip replacements are highly effective operations for patients with severe pain in these joints, and opioids are the main drugs used for acute pain management after such surgeries. However, little is known about long-term patterns of opioid use after joint-replacement surgery. This information is especially important as such surgeries become even more frequent as the US population ages and the “opioid epidemic” continues to produce dramatic increases in opioid use, misuse, and overdose.
The researchers analysed patterns of opioid use in 574 patients undergoing knee or hip arthroplasty. Patients were followed up at 1, 3, and 6 months after surgery to assess rates of and risk factors for long-term opioid use.
About 30% of the patients were taking opioids prior to their joint replacement surgery. Of this group, 53% of knee replacement patients and 35% of hip replacement patients were still taking opioids at 6 months after surgery.
Patients who were not taking opioids prior to surgery were less likely to report persistent opioid use — about 8% in the knee group and 4% in the hip group continued to take opioids at the 6-month follow-up. Although these are relatively small percentages, this suggests that a portion of patients who were opioid-naïve prior to surgery will become new chronic opioid users following arthroplasty.
The strongest predictor of long-term opioid use was taking high-dose opioids before joint replacement surgery. For patients in the highest preoperative dose group (equivalent to more than 60 mg of oral morphine per day), the predicted probability of persistent opioid use at 6 months was 80%.
Among patients not previously taking opioids, those with higher pain scores the day of surgery — both in the affected joint and overall body pain — were more likely to report persistent opioid use at 6 months. Opioid use was also more likely for patients who scored higher on a measure of pain catastrophizing than those with depressive symptoms.
For all patients, reductions in overall body pain were associated with decreased odds of being on opioids at 6 months. However, improvement in knee or hip pain after joint replacement did not reduce the likelihood of long-term opioid use.
Persistent opioid use after knee or hip replacement surgery may be more common than previously reported, the results suggest. Importantly, continued opioid use is not necessarily related to pain in the affected joint.
“We hypothesise that the reasons patients continue to use opioids may be due to pain in other areas, self-medicating affective distress, and therapeutic opioid dependence,” the authors wrote.