Review Question - QID 217996

This patient has a draining sinus tract in the setting of a prior total knee arthroplasty (TKA). As one of the major criteria for diagnosing a periprosthetic joint infection (PJI), a draining sinus tract is diagnostic, and the patient should begin definitive treatment. The patient should undergo aspiration of the knee to identify the organism, which could also be obtained in the operating theatre when removing their current implant.

The Musculoskeletal Infection Society (MSIS) introduced its initial criteria for periprosthetic joint infection (PJI) in 2011 in order to gain improvements in diagnostic confidence and research collaboration regarding this condition. The MSIS defined major and minor criteria for the establishment of diagnosing a PJI (Illustration A). Since that time, there have been multiple validation studies confirming the utility and accuracy of the MSIS PJI criteria. In cases where there are questionable findings for a PJI, the orthopaedic surgeon should follow the appropriate workup to include obtaining serum labs (ESR, CRP, WBC, etc) followed by aspiration of the knee with synovial fluid analysis (WBC, PMN %, CRP, alpha-defensin). However, if one of the major criteria is present (draining sinus tract to the prosthesis or two positive cultures of the same organism), the diagnosis of PJI is confirmed and should be treated accordingly. Within the United States, a two-staged revision protocol is currently the gold standard over one-staged revision.

Parvizi et al. performed a retrospective review of all patients undergoing revision total hip arthroplasty (THA) and TKA at three large academic centers over a fifteen-year period. They obtained an appropriate workup for each patient using the 2011 MSIS criteria and utilized regression analysis to calculate the weighted value of each diagnostic tool (labs, microbiology, etc). Using these weighted values, the authors established both minor and major indicators for the diagnosis of PJI and a general diagnostic protocol to follow.

Diaz-Ledezma sought an international multidisciplinary consensus on the treatment of PJI treatment utilizing the Delphi method. They invited 159 international experts from 17 countries to participate with roughly 50 final experts involved. The group concluded with a consensus on three dimensions to define what would be considered a successful treatment of PJIs: (1) eradication of infection (2) no need for further subsequent surgical intervention (3) no mortality related to the PJI.

Figure A shows a drain sinus tract that probed to the prosthesis in the intra-articular space. Illustration A is taken from the Parvizi article and shows the minor and major criteria to establish the diagnosis of a PJI.

Incorrect Answer Choices:
Answer 1: As discussed, this patient has already met the diagnostic criteria for chronic PJI. There is no need to wait to establish the diagnosis before beginning treatment.
Answer 2: Performing a bedside procedure followed by prescribing oral antibiotics would not be prudent, as this patient should undergo formal operative removal of their current TKA implant with the placement of an antibiotic spacer.
Answer 3: This patient has a chronic PJI. Debridement, antibiotics, and implant retention (DAIR) could be considered within the first 4-6 weeks after initial TKA surgery. However, it has been seven years and a two-staged revision is most appropriate. It should be noted that DAIR procedures can certainly be considered in very sick patients who may not be able to tolerate the two staged gold-standard treatments.
Answer 4: One staged revision is encouraged by some European countries; however, one staged surgery is not the gold standard within the United States for the treatment of chronic PJIs. There are large-scale, multi-site, randomized control trials currently underway to compare these two treatment modalities (ClinicalTrials.Gov identifier: NCT02734134).