In Vivo Systemic Vancomycin Determination from Polymethyl Methacrylate and Morselized Bone Allograft Used in Two Stage Septic Knee Revision Arthroplasty

Introduction: This paper examines the use of local antibiotic therapy in one-stage septic revision surgery for late periprosthetic joint infections (PJIs). This case study suggests that morselized bone allografts impregnated with antibiotics in powder form are a preferable alternative to polymethyl methacrylate (PMMA) because they can generate higher local antibiotic concentrations. Current research also recommends using vancomycin and aminoglycosides as the preferred choice of antibiotics, as they may have low diffusion in tissues when administered intravenously, but are effective when administered locally. The article emphasizes the importance of achieving high local antibiotic concentrations to eradicate bacterial biofilms and provides guidelines for the preparation of bone allografts. Case report: The paper assesses the case study of a 68-year-old male patient who underwent two-stage total revision surgery for a late septic failure of the endoprosthesis (approximatively one year after implantation). The first stage involved removing the implant, debridement, lavage, and setting a fixed spacer manually made from polymethyl methacrylate impregnated with 4 g of vancomycin. The second stage of revision surgery utilized a morselized bone allograft impregnated with 4 g of vancomycin as a means of local antibiotic therapy and bone defect coverage. Systemic levels of vancomycin were measured at 4, 8, 12 and 24 hours respectively after surgery. During this period, no systemic vancomycin was administered. After the second stage was carried out and the testing was carried out, systemic vancomycin therapy was initiated and the plasma levels of the drug were assessed and subsequently therapeutic doses were adjusted. Conclusions: Vancomycin loaded bone allograft achieved higher systemic concentrations that its polymethyl methacrylate counterpart, when being manually loaded with the same amount of antibiotic. Nonetheless, the levels were well below nephrotoxic levels, indicating that this may be a valuable tool for local means of antibiotic therapy in selected patients that could not endure such a systemic therapeutic regiment. For septic revisions, antibiotic loaded bone allograft holds a valuable place in the surgical arsenal of local antimicrobial treatment, by far exceeding that of the polymethyl methacrylate.