The 2023, James A. Rand, MD, Young Investigator’s Award, which recognizes young investigators who demonstrate clinical excellence in knee-related research was presented at the recently concluded American Association of Hip and Knee Surgeons (AAHKS) annual meeting to lead author Jason Kreinces, B.S. and co-authors Ittai Shichman, M.D., Mackenzie A. Roof, M.D., M.B.A., Hayley Raymond, B.S., Alana Prinos, B.S., Itay Ashkenazi, M.D., Ran Schwarzkopf, M.D., M.Sc. and Vinay K. Aggarwal, M.D.
Their award-winning study explored the effectiveness of diagnostic testing for periprosthetic joint infection (PJI). In their study, the research team collected data for patients who had received revision total hip arthroplasty (THA) or total knee arthroplasty (TKA) for suspected PJI between 2018 and 2020 (minimum two-year follow-up).
They collected perioperative data and lab results, and dichotomized cases based on whether they met the 2018 Musculoskeletal Infection Society (MSIS) criteria for PJI. In total, 204 revision total knee arthroplasty and 158 revision total hip arthroplasty cases suspected of PJI were reviewed.
The researchers determined that nearly 100% of the cases met the 2018 MSIS criteria for being “infected”—without having to use an alpha-defensin or synovial CRP (C-reactive protein) test.
“The most important thing is to remember that clinical suspicion of infection should guide the workup. Ideally, when possible, an algorithmic approach to the workup is recommended and we found in our paper that using the ESR [erythrocyte sedimentation rate], CRP, synovial WBC [white blood count], PMN [polymorphonuclear neutrophil] and cultures are sufficient to diagnose PJI in more than 96% of cases,” said Vinay K. Aggarwal, M.D., an assistant professor in the department of orthopaedic surgery at the New York University Grossman School of Medicine.
Alpha Defensin Synovial Testing Less Effective Than Expected
“I would emphasize that there was significant early enthusiasm for the alpha defensin synovial testing for periprosthetic joint infection,” stated Dr. Aggarwal to OTW. “Some of this enthusiasm has now waned with recent data including in our own study. This is why we felt it was important to highlight that some of these extraneous tests that are new or are not required to proceed with periprosthetic joint infection diagnosis.”
“Furthermore, I do not think it was a surprise to us that nearly 100% of our potential infection cases could be diagnosed using the 2018 criteria without the use of synovial alpha defensin and or synovial CRP. This is what drove the impetus for the study in general given our own experience with not having to use this workup on the majority if not all of the cases.”
“We want to highlight and get the word out that some of this testing can go by the wayside if you stick to classic clinical suspicion and readily available low-cost testing.”
Employing the Stepwise Algorithmic Approach
OTW asked Dr. Aggarwal for details about the stepwise algorithmic approach. He said, “A stepwise algorithm in our practice for periprosthetic joint infection always starts with a high index of clinical suspicion.”
“This would include a patient who had a previously well-functioning joint replacement and now has pain, swelling, redness that was not there before. Obviously in the acute postoperative phase significant drainage that is not resolving, wound issues, or worsening swelling and pain would also spark a workup.”
“Thereafter we start with simple laboratory testing including ESR and CRP. If either of these is elevated in our practice, we turned towards a synovial aspiration where we sent testing for cultures and cell count that includes white blood cells and polymorphonuclear differential (PMN%).”
“This workup is capable of diagnosing periprosthetic joint infection in the vast majority of cases. Occasionally we need additional intraoperative culture data to confirm the suspicion and with these combined we were able to achieve nearly 100% diagnosis rate in our study.”
“The biggest issue with cost is in relationship to individual hospital contracts with laboratory testing,” stated Dr. Aggarwal to OTW. “With the above test that I have mentioned the cost is so low that it is almost not necessary to keep an eye on them. When you start to introduce new technology and newer testing without a standardized approach this is where costs can elevate, and practice deviation of protocol leads to less than necessary or acceptable expenditures.”
