Which type of bone releases the most vancomycin? Comparison of spongious bone, cortical powder and cortico-spongious bone.

Abstract

Bone infections can be challenging to treat and can lead to several surgeries and relapses. When a graft is needed, cavitary bone loss can be grafted with cancellous or cortical bone. Both can be used for grafting. However, the antibiotic releasing capacity of these grafts has not been compared. Which type of bone is best at releasing the most antibiotic has not been well established. The aim of this study was to determine which type of bone is best for antibiotic release when the bone is suffused with antibiotics by the surgeon. The hypothesis is that there would be a difference between the type of bone tested due to different release capacities of cortical and cancellous bone. This was an experimental study. Cortical spongy bone in chips, Spongy bone in chips and demineralized cortical bone powder were compared. For each type of bone, 5 samples were tested. Processed and decontaminated grafts were freeze-dried to be kept at room temperature. The primary endpoint was the amount of vancomycin released by the graft as it affects the concentration of antibiotic around the graft in clinical practice. The procedure for the study consisted of full graft immersion in a vancomycin solution. Then, the liquid was removed with aspiration. In order to measure the quantity of antibiotic released, the bone was put into distilled water in agitation in a heated rocker at 37°C. After 30min of soaking, 1mL of the liquid was removed. The same extraction process was also carried out after 60min soaking, 2h, 3h, 24h, and 48h. No differences were found between each type of bone relative to the concentration of vancomycin released at each time of the assessment. There was a significant difference in the weight of the bone with a higher weight for the cortical powder (1.793g) versus cortical spongy bone and spongy bone (1.154g and 1.013g) with a p value < 0.0001. A significant difference was seen in the weight of the bone with vancomycin after the aspiration of the liquid with 3.026g for cortical powder, 2.140g and 2.049g for the cortical spongy bone and the spongy bone with a p value < 0.0001. In daily clinical practice, one can use cancellous bone, cortico-cancellous bone or cortical powder in order to add vancomycin to a bone graft. Our results show the release kinetics of the soaked allografts. With a maximum of 14mg/mL in the first minutes and a rapid decrease it shows a pattern comparable to antibiotic loaded bone cement. The method used appears favourable for prophylactic use, protecting the graft against contamination at implantation, but is not sufficient for treating chronic bone infection. LEVEL OF EVIDENCE: V.