To prevent infections after orthopaedic surgery, intravenous antibiotics are administered perioperatively. Cefazolin is widely used as the prophylactic antibiotic of choice. Systemic antibiotic therapy may however be less effective in longstanding surgery where bone allografts are used. Bone chips have been shown to be an effective carrier for certain types of antibiotics and may provide the necessary local antibiotic levels for prophylaxis. To be efficient a prolonged release is required. In contrast to vancomycin with proven efficient prolonged release from Osteomycin, this has not been described for cefazolin. We developed a protocol to bind cefazolin to bone chips by means of a hydrogel composed of proteins naturally present in the human body. Three types of bone chips were evaluated: fresh frozen, decellularized frozen and decellularized lyophilized. Bone chips were incubated with 20 mg/ml cefazolin or treated with liquid hydrogel containing either 1 mg/ml fibrin or 1 mg/ml collagen and 20 mg/ml cefazolin. The cefazolin hydrogel was distributed in the porous structure by short vacuum treatment. Bone chips with cefazolin but without hydrogel were either incubated for 20 min- 4h or also treated with vacuum. Cefazolin elution of bone chips was carried out in fetal bovine serum and analysed by Ultra Performance Liquid Chromatography – Diode Array Detection.Aim
Method
Vancomycin -impregnated bonechips from a human morselized femoral head allograft (BCs) are used in orthopaedic surgery to treat infections. Literature suggests that bonechips can be efficient vancomycin carriers, but due to the diversity in the type of bonechips, of impregnation and of method used to evaluate AB release, there are no uniform guidelines. We performed an in vitro study to examine the release of vancomycin from solution-impregnated deepfrozen processed bonechips. Quantification was performed using a fully validated chromatographic method. Results were compared with the elution-profile from Osteomycin®, a commercially available lyophilised processed bonegraft. Different vancomycine impregnation-concentrations and impregnation-durations of frozen processed bonechips were investigated. After impregnation, bonechips were rinsed with saline in order to determine only the absorbed vancomycin. Elution was performed in newborn calf serum at 37°C. Eluted vancomycin concentrations were determined using Ultra Performance Liquid Chromatography – Diode Array Detection (UPLC-DAD). In addition an elution study was performed on the commercially available Osteomycin®, bone chips containing vancomycine. Using processed frozen bonechips, an impregnation-concentration of minimum 100 mg/mL during 10 minutes delivers the desired local concentration (therapeutic window 25 – 1000 mg/L) for 3 days. Longer impregnation time at this concentration had no effect. Osteomycin®: delivers the desired local concentration for 8 days in our experimental setting. Literature suggests that freshfrozen BCs can be used as carrier for vancomycin through solution-impregnation [1,3]. There is however much less information on the carrier-capacities of frozen processed bonechips, a type used in our hospital. Our impregnation-protocol was based on that of Mathyssen et al., but with direct quantification of elution concentrations. Impregnation with vancomycine 100 mg/mL during 10 minutes results in a release above the desired concentration for 3 days, which seems too short when treating bone-infections. Osteomycin®, shows a substantially longer elution [2]. Vancomycin-solution impregnation of frozen processed bonechips may not be sufficient to obtain the desired release-characteristics for the treatment of bone-infections.
