LONG-TERM ELUTION OF ANTIBIOTICS FROM BONE-CEMENT - AN IN-VIVO STUDY USING THE PROSTHESIS OF ANTIBIOTIC-LOADED ACRYLIC CEMENT (PROSTALAC) SYSTEM

A prospective study of 49 patients undergoing a modified 2-stage excha nge arthroplasty for infected total hip and knee arthroplasties using the prosthesis of antibiotic-loaded acrylic cement (PROSTALAC) system with a variety of doses of tobramycin and vancomycin was performed. Th e intra-articular concentrations of tobramycin and vancomycin were mea sured at the time of removal of the PROSTALAC temporary spacer and rei mplantation of a definitive joint arthroplasty prosthesis, at a mean 1 18 days following initial implantation. The 95% confidence interval of the intra-articular concentration of tobramycin (4.35-123.88 mg/L) wa s entirely above the breakpoint sensitivity limit for sensitive organi sms when at least 3.6 g of tobramycin was used per package of bone-cem ent but was entirely below it when at most 2.4 g was used. Vancomycin elution was not as good; however, detectable levels were still present in most patients. There was a statistically significant increase in t he elution of vancomycin when the dose of tobramycin was increased fro m at most 2.4 g to at least 3.6 g. The dose of vancomycin in the cemen t did not influence the elution of either tobramycin or vancomycin. On the basis of these results, the use of at least 3.6 g of tobramycin a nd 1 g of vancomycin per package of bone-cement is recommended when an tibiotic-loaded cement spacers are used in 2-stage exchange arthroplas ty for infected total hip and knee arthroplasties.