Analgesic drug consumption increases after knee arthroplasty: a pharmacoepidemiological study investigating postoperative pain.

Knee arthroplasty remains the gold standard in the treatment of severe osteoarthritis. Chronic postoperative pain has been reported with a prevalence ranging from 15% to 47%. The aim of this study was to compare analgesic drug consumption before and after surgery as an indicator of pain after knee surgery. A pharmacoepidemiological method comparing analgesics and antineuropathic issues 1 year before and 1 year after surgery was used. All patients who underwent knee arthroplasty in the Midi-Pyrenees region (2.5 million inhabitants) were identified through the Health Insurance System Database. Increase of drug issues (all analgesics, antineuropathic drugs, strong opioids) was calculated and compared between several periods surrounding the surgery (12 months, 2 months, and 10 months before and after the knee arthroplasty). A multivariate logistic regression model was used to identify factors associated with chronic postoperative pain. The study included 1939 patients. An increase in analgesic, antineuropathic, and opioid drug consumption was observed the year after the surgery in 47.3%, 8.6%, and 5.6% of patients, respectively. Multivariate analysis found a significant association between type of surgery (total knee vs unicompartmental arthroplasty) and analgesic consumption 1 year after surgery, and between preoperative pain and psychiatric vulnerability and increase in neuropathic drug dispensing. Conversely, older age was considered as a protective factor. This study revealed that an increase in the issue of different analgesic drugs is present in half of patients 1 year after knee arthroplasty. Several associated factors of drug consumption (preoperative pain, type of surgery, and psychiatric disorder) were identified.