Predictors of Prolonged Analgesic Use after Joint Replacement

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Eric Secrist, MD in response to a recent study in Arthritis Research & Therapy.

There has been a proliferation of research regarding postoperative opioid usage after joint arthroplasty due to the widespread opioid epidemic. But Rajamäki and colleagues from Tampere University in Finland took the unique approach of also analyzing acetaminophen and NSAID usage in addition to opioids. The authors used robust data from Finland’s nationwide Drug Prescription Register, which contains reliable information on all medications dispensed from pharmacies, including over-the-counter drugs.

After excluding patients who underwent revision surgery or had their knee or hip replaced for a diagnosis other than osteoarthritis, the authors analyzed 6,238 hip replacements in 5,657 patients and 7,501 knee replacements in 6,791 patients, all performed between 2002 and 2013. The mean patient age was 68.7 years and the mean BMI was 29.

One year postoperatively, 26.1% of patients were still filling prescriptions for one or more analgesics, including NSAIDs (15.5%), acetaminophen (10.1%), and opioids (6.7%). Obesity and preoperative analgesic use were the strongest predictors of prolonged analgesic medication usage 1 year following total joint arthroplasty. Other predictors of ongoing analgesic usage included older age, female gender, and higher number of comorbidities. Patients who underwent knee replacement used the 3 analgesics more often than those who underwent hip replacement.

This study had all of the limitations inherent in retrospective database analyses. Additionally, it was not possible for the authors to determine whether patients took analgesic medications for postoperative knee or hip pain or for pain elsewhere in their body. Finally, the authors utilized antidepressant reimbursement data as a surrogate marker for depression and other medications as a surrogate for a Charlson Comorbidity Index.

Figure 2 from this study (shown below) reveals 2 important findings. First, total joint arthroplasty resulted in a significant decrease in the proportion of patients taking an analgesic medication, regardless of BMI. Second, patients in lower BMI categories were less likely to use analgesics both preoperatively and postoperatively.

The findings from this study may be most useful during preoperative counseling for obese patients, who often present with severe joint pain but are frequently told they need to delay surgery to lose weight and improve their complication-risk profile. Based on this study, those patients can be counseled that losing weight will not only decrease their complication risk, but also decrease their reliance on medications for the pain that led them to seek surgery in the first place.

Eric Secrist, MD is a fourth-year orthopaedic resident at Atrium Health in Charlotte, North Carolina.

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