Interdisciplinary Study Provides Guidance on Total Knee Replacement Pain Management

PSI Spotlights Photo of Dr. Kim Wong (Health Sciences North) for PSI Spotlight Posted: January 18, 2020

“Because PSI is geared toward physicians, there’s almost an unwritten understanding of why you’re doing the research and that it’s for the end goal of treating our patients better. We don’t have to prove that our research has clinical relevance.” – Dr. Kim Wong

Total knee replacement is a common procedure done in many hospitals, and it is known to be associated with a significant amount of post-operative pain. Many interventions exist to address this pain, but since a myriad of techniques can be used, choosing the optimal technique can be a source of much discussion in the operating room. Local practices vary based on the location and time of team members’ training, and orthopedic and anesthesia teams may have different views of the best approach to use.

“Everyone seems to have differing opinions about which analgesic intervention to use perioperatively,” says Dr. Kim Wong, an anesthesiologist at Health Sciences North in Sudbury. “But at the end of the day, everyone wants the patient to go home with as little pain as possible and as soon as possible.”

Evidence on the subject has been definitively inconclusive so far, with mostly small, comparative single intervention studies. Dr. Wong saw the need for a larger interdisciplinary study that compared different combinations of interventions used in real world practice on patient outcomes, with the goal of providing clarity on the best approach to use.

She received a grant from PSI Foundation to lead a five-arm randomized blinded trial that involved both the orthopedic and anesthesia departments at Health Sciences North. They compared different combinations of three pain management interventions used before and during total knee replacement surgery: intrathecal morphine, femoral nerve block (a regional anesthetic injected into the upper thigh) and periarticular infiltration (local anesthetic and anti-inflammatory injected around the knee joint). They evaluated whether intrathecal morphine alone, different pairs of the interventions or a combination of all three affected time for patients to reach discharge criteria, their pain scores and their narcotics needs after surgery to control pain.

The study team found that all of the arms of the study met discharge criteria, with patients being discharged by the afternoon of the second day. But further analysis showed that any combination of two interventions had better pain outcomes than intrathecal morphine alone, though the combination without intrathecal morphine resulted in less itchiness. Surprisingly, the combination of three interventions did not result in significantly better outcomes.

“I hope the study gives surgeons and anesthesiologists comfort that they can choose the interventions that they do best, as long as they provide two,” says Dr. Wong. “In my own clinical practice, I can tailor my approach to accommodate a patient’s individual medical history with the comfort of knowing that I’m not placing them at a disadvantage of getting out of the hospital faster or with less pain.”

Dr. Wong says that it was ambitious to lead a five-arm trial with enough statistical power to be clinically relevant, and the study team did have challenges with recruitment. As a result, PSI Foundation funding was essential to the study’s success. “It allowed us to address the challenges without having to worry about stopping the study or not having a powered study that would lend less credibility to the results,” she says. “The funding allowed the financial buffer to reflect the realities of clinical research.”

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