According to data published in Open Forum Infectious Diseases, treatment nonresponse  in prosthetic hip and knee joint infection (PJI) is common and the risk factors difficult to modify.

Investigators conducted a retrospective cohort of individuals who underwent prothesis removal as a result of a prosthetic joint infection at 5 Toronto, Canada, hospitals. Treatment nonresponse was defined as recurrent prosthetic joint infection, amputation, death, or chronic antibiotic suppression and risk factors abstracted by chart review.

The cohort included 533 individuals who were followed for a median of 814 (interquartile range [IQR], 235- 1530) days. In 19% of individuals, a 1-stage exchange was performed and a 2-stage procedure was performed in 88% (377/430). Treatment nonresponse occurred in 24.8% at 2 years and 53% (56/105) of recurrent PJIs were caused by a different bacterial species. Treatment nonresponse occurred in 36% of 1-stage and 32% of 2-stage procedures (P =.06) at 4 years.

Results also demonstrated that prosthetic joint infections were caused by a monomicrobial infection in 67%, polymicrobial infection in 9%, and were culture-negative in 24%; the most commonly isolated bacteria were coagulase-negative staphylococci (32%), followed by S aureus (19%), Gram-negative bacilli (10%), and enterococci (8%). Treatment nonresponse followed a similar pattern.


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The characteristics associated with nonresponse included liver disease (adjusted hazard ratio [aHR], 3.12; 95% CI, 2.09-4.66), the presence of a sinus tract (aHR, 1.53; 95% CI, 1.12-2.10), preceding debridement with prosthesis retention (aHR, 1.68; 95% CI, 1.13-2.51), a 1-stage procedure (aHR, 1.72; 95% CI, 1.28-2.32), and infection due to Gram-negative bacilli (aHR, 1.35; 95% CI, 1.04-1.76).

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The investigators acknowledged that the detection strategy for prosthetic joint infection was imperfect and may have resulted in missed individuals. Also, only individuals who underwent an operation for the treatment of prosthetic joint infection were included because the number of patients treated with antibiotics alone is expected to be small. Furthermore, individuals treated medically often opt to focus on attenuating circumstances, thus differentiating them from patients whose goal is infection eradication. Some characteristics potentially associated with surgical site infection, like smoking or surgeon volume, also could not be obtained. Finally, the retrospective nature of the study increased the possibility that unmeasured confounders might have affected the results.

The results showed that, “prosthetic hip and knee joint infections are challenging to eradicate, with failure rates >20% even in the setting of complete prosthesis removal.” Researchers also found that identified risk factors were not modifiable, a finding consistent with previous research. Therefore, there is an urgent need to improve treatment paradigms and interventions.

Reference

Kandel CE, Jenkinson R, Daneman N, et al. Predictors of treatment failure for hip and knee prosthetic joint infections in the setting of 1- and 2-stage exchange arthroplasty: A multicenter retrospective cohort. Open Forum Infect Dis. 2019;6(11):ofz452.