These authors compared two different methods for identifying successful treatment of periprosthetic joint infections (PJI).
The first was that of the Musculoskeletal Infection Society in which successful treatment was defined as "infection control" with or without suppressive antibiotic therapy. "Failure" was essentially defined as a repeat surgery or death, as seen below.
The second was that of the Delphi-based consensus in which "success" was defined as infection eradication, evidenced by a healed surgical wound without drainage or a fistula, no documented infection recurrence, no mortality related to PJI (such as sepsis or necrotizing fasciitis), and no subsequent surgical intervention for infection after the second stage of the reimplantation procedure. 71% of the participants in the consensus meeting agreed that 2 years was an acceptable time period after definitive surgery for PJI when considering short-term results. It is of note that this study concerned hip and knee infections, which are usually caused by virulent organisms that can cause draining sinuses, sepsis, necrotizing fasciitis, and severe systemic illness.
Interestingly, neither the MSIS or the Delphi criteria use culture results to evaluate the "infection control" or "infection eradication" after treatment for periprosthetic joint infection. Without this information, how can one be confident that the infection is controlled or eradicated?
In the practice of shoulder arthroplasty, the landscape is more complex because the most common organisms causing shoulder PJI are those commensal on normal skin: Cutibacterium and Coagulase-negative Staphylococcus; these organisms rarely cause draining sinuses, sepsis, necrotizing fasciitis, or severe systemic illness. Instead, these organisms typically have a "stealth" onset consisting of pain and stiffness presenting months or years after the index arthroplasty. The indications for re-operating on a painful stiff arthroplasty are not well defined. The diagnosis can only be dependably made by the recovery of two or more positive cultures from deep tissue or prosthesis explant specimens. For the same reason, diagnosis of a "failed" or a "successful" treatment cannot reliably be made without a second surgical procedure. The indications for performing a second revision on shoulder that remains painful and stiff after the first arthroplasty revision are not well defined.
Perhaps the most robust definition of a failed revision for Cutibacterium PJI is a second revision at which time multiple deep specimens are culture positive for Cutibacterium. Without a second procedure, the identification of success and failure in the management of Cutibacterium PJI remains elusive.
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