Analgesic drugs are recommended to treat pain caused by osteoarthritis, and joint replacement should decrease the need for them. We aimed to determine the user rates of analgesic drugs before and after joint replacement.
All patients who underwent a primary hip or knee replacement for osteoarthritis from 2002 to 2013 in a region of 0.5 million people were identified. Patients with revision or other joint replacements during the study period (operation date +/- two years) were excluded, leaving 6238 hip replacements (5657 patients) and 7501 knee replacements (6791 patients) for analyses. Medication data were collected from a nationwide Drug Prescription Register and the prevalence (with its 95% confidence intervals) of acetaminophen, non-steroidal anti-inflammatory drugs (NSAIDs), mild opioids, strong opioids, and medications used for neuropathic pain was calculated in three-month periods two years before and after surgery.
Between two years and three months preoperatively, the proportion of patients who redeemed at least one type of analgesic drug increased from 28% (95% CI, 27-30%) to 48% (47-50%) on hip replacement patients and from 33% (32-34%) to 41% (40-42%) on knee replacement patients. Postoperatively, the proportions decreased to 23% (22-24%) on hip and to 30% (29-31%) on knee patients. Hip replacement patients used more NSAIDs (34% (32-35%) hip vs 26% (25-27%) knee, p < 0.001), acetaminophen (14% (13-15%) vs 12% (11-13%), p < 0.001), and mild opioids (14% (13-15%) vs 9% (8-9%), p < 0.001) than knee patients preoperatively, but postoperatively hip patients used less NSAIDs (12% (11-13%) vs 16% (15-16%), p < 0.001), acetaminophen (9% (8-10%) vs 11% (11-12%), p < 0.001), and mild opioids (5% (5-6%) vs 8% (7-8%), p < 0.001).
Use of analgesic drugs increases prior to joint replacement, and is reduced following surgery. However, a considerable proportion of patients continue to use analgesics in two-year follow-up.