"With these study results, we'd encourage physicians to consider discussing long term implications of opioid therapy with their patients," says Elena Losina, Ph.D., lead author, director of the Policy and Innovation Evaluation in Orthopedic Treatments Center and co-director of the Orthopedics and Arthritis Center for Outcomes Research at Brigham and Women's Hospital. "Although each patient case is different, patients and physicians should discuss the potential impact of using opioids in patients with knee osteoarthritis who are likely to consider total knee replacement within the next two years."
Knee osteoarthritis is a condition associated with significant activity limitation and chronic pain. While a TKR is an effective treatment in relieving pain and restoring function, patients spend an average of 13 years using non-surgical options for pain management including the use of non-steroidal anti-inflammatory drugs, physical therapy, and intra-articular injections. As the authors quote in the paper, the United States has spent over $1.5 billion annually on prescription opioids for people with knee osteoarthritis. Additionally, opioid utilization has increased drastically, with nearly 40 percent of Medicare patients with knee osteoarthritis receiving at least one opioid prescription in 2009. Although previous studies have suggested that using opiods preoperatively is associated with poor pain outcomes, the research was based on limited sample sizes and pain catastrophizing was not considered.
The team reviewed data from 156 patients who had TKR at an average age of 66. They collected patient-reported outcomes and demographic data both before and six months after surgery, and abstracted data regarding opiod use from the patients' medical records. Researchers found that prior to surgery, 23 percent of patients had at least one opioid prescription.
Using standard pain scales (Pain Catastrophizing Scale, the Western Ontario and the McMaster Universities Osteoarthritis Index (WOMAC)), researchers quantified the pain experiences of patients undergoing TKR. Researchers used sophisticated analytic methods to compare the change in the WOMAC pain score six months after knee surgery and establish the difference between patients who had and those who had not used opioids before TKR. Researchers found that the patients who used opioids prior to surgery had about 9 percent less pain reduction at six months following surgery.
"Our findings support previous research that indicated preoperative opioid use was associated with worse clinical outcomes. This data demonstrates that preoperative opioid use may also lead to lesser pain relief in the early postoperative period," said Losina.
The researchers also note that since the U.S. spends over $1.5 billion annually on prescription opioids for patients with knee osteoarthritis, and nearly $30 billion on illicit use, reducing the use of opioids may decrease their harmful effects. Clinicians and policy makers may consider limiting the use of opioids prior to TKR to optimize post-TKR pain relief.
Find more information on the study here.