What Causes Failure of a 2-Stage Exchange for PJI?
Dr. Omar Behery and Dr. Scott Sporer answer ICJR’s questions about the organisms responsible for reinfection after 2-stage exchange in hip and knee arthroplasty patients treated for a periprosthetic joint infection.
ICJR: What question did you and your co-authors want to answer with this study?
Omar A. Behery, MD, MPH: The etiology of reinfection following a 2-stage exchange for periprosthetic joint infection (PJI) in hip and knee arthroplasty patients remains unclear, although there is contemporary evidence that these reinfections are due to different organisms than those implicated in the index infection.
This study was conducted to determine whether the organism responsible for the reinfection was susceptible to the antibiotics administered during the initial 2-stage exchange. If susceptible, the reinfecting organism may have been a new organism; if not susceptible, the reinfecting organism may have been present but not identified at the time of index infection and, therefore, inadequately treated.
ICJR: What did you conclude about failures after 2-stage exchange?
Dr. Behery: The majority of reinfections in this study due to new organisms (64%) were secondary to organisms susceptible to the initially indicated antibiotic regimen. This suggests that these were new reinfecting organisms, as opposed to persistent microbes that were not detected during index treatment and, thus, were inadequately treated.
ICJR: How did you reach your conclusions? What was your study cohort and what did you find with your analysis?
Scott M. Sporer, MD: This was a retrospective study of 30 failed 2-stage exchange revisions for chronic hip (11) and knee (19) PJIs over a 14-year period. We included only patients who:
- Met the PJI criteria of the Musculoskeletal Infection Society
- Were positive for organisms with described antibiotic sensitivities (no fungal organisms)
- Had undergone a 2-stage exchange revision
The antibiotic sensitivity profiles of these organisms were reviewed and compared by type, “new” or “repeat,” based on phenotypic identity and susceptibility. Organisms in the “new” category were further identified as “susceptible” or “non-susceptible” to the antibiotics administered for the index infection.
Of the 30 reinfections, 25 were due to a new organism, of which 64% were susceptible to the index antibiotic regimen. As Dr. Behery noted, this suggests that these were new reinfections rather than persistent and undetected during the initial treatment.
ICJR: Why is this significant for clinical practice?
Dr. Sporer: The findings of this study indicate that the majority of reinfections may be due to new organisms and are likely new infections, given the high rate of susceptibility to the prior antibiotic regimen.
This has important implications for the potential impact of host-related risk factors that can put these patients at risk for “new” PJIs. The risk factors include immune suppression, uncontrolled diabetes mellitus, malnutrition, and smoking, some of which may be modifiable.
Larger studies are needed to corroborate our findings.
Egbulefeu FJ, Yang J, Chen AF, Sporer SM, Segreti J, Austin M, Della Valle CJ. Recurrent failures after two-stage exchanges are secondary to new organisms not previously covered by antibiotics (Paper 004). Presented at the 2021 Annual Meeting of the American Academy of Orthopaedic Surgeons, August 31-September 3, San Diego, California.
About the Experts
Omar A. Behery, MD MPH, is an orthopaedic surgeon at Rush University Medical Center, Chicago, Illinois. Scott M. Sporer, MD, is an orthopaedic surgeon and Professor of Orthopaedics at Rush University Medical Center, Chicago, Illinois.
Disclosures: Dr. Behery and Dr. Sporer have no disclosures relevant to this article.