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Patients presenting with prosthetic joint infections of a total knee replacement who are treated with an antibiotic spacer will be observed prospectively for their response to treatment and antibiotic elution profiles will be measured post-operatively utilizing mass spectrometry from synovial fluid acquired as part of standard of care in the management of prosthetic joint infection. Secondary outcomes including post-operative complications, re-operation rates, and re-admission rates will also be compared.

The current study aims to assess the surgical and patient-reported outcomes and in vivo antibiotic elution profile of the management of total knee arthroplasty (TKA) prosthetic joint infection (PJI). Within the standard of care, TKA PJI is treated via a resection arthroplasty and antibiotic cement spacer placement. Patients will be enrolled if they are undergoing surgical management for a chronic TKA PJI and will receive surgical treatment according to the standard of care. In the post-operative period, patients will be monitored for surgical and patient-reported outcomes including re-operation rate, pain scores, complication rates, and re-infection rates. Synovial fluid obtained from intra-articular postoperative drains and at postoperative knee aspirations during reimplantation evaluations will also be utilized for antibiotic concentration quantification via mass spectrometry, if sufficient specimen is available. Patient who undergo surgical management for their chronic TKA PJI will then have their measured antibiotic elution concentrations compared. The study hypothesizes that patients undergoing treatment of a PJI with antibiotic spacer + antibiotic cement spacer will have better surgical and patient-related outcomes with higher antibiotic elution concentrations. These improved outcomes would include lower re-operation rates, lower pain scores, lower wound healing complications, and higher rates of second stage re-implantation observed in patients with higher antibiotic elution concentrations.

Specific aims:

1. To evaluate the antibiotic elution profile and post-operative intra-synovial concentrations in the treatment of chronic PJI after TKA.
2. To evaluate surgical and patient-related outcomes in chronic TKA PJI patients following implant resection and knee spacer placement, including amount of post-operative drain output, wound healing complications, 30- and 90-day risk of re-operation, pain scores, and rate of second stage re-implantation.

Inclusion Criteria:

• Patients planned for treatment of a total knee arthroplasty prosthetic joint infection
• Patients greater than 18 years of age
• Patients able to provide informed consent

Exclusion Criteria:

• Prior history of ipsilateral or contralateral prosthetic joint infection warranting operative management
• Patients less than 18 years of age
• Patients unable to provide informed consent.

The study population will comprise of patients who have had a previous total knee arthroplasty (TKA), presenting with clinical and laboratory findings concerning for a chronic TKA prosthetic joint infection (PJI) undergoing staged surgical management consisting of resection arthroplasty followed by mobile antibiotic spacer placement. Patients who have had prior surgical treatment of a PJI and are less than 18 years of age will not be included in the study population.

There are no plans at present to make individual participant data (IPD) available to other researchers, however we may share de-identified data with other researchers in the future.