Masquelet technique: Effects of vancomycin concentration on quality of the induced membrane.

<bold>Purpose: </bold>The purpose of this study was to determine the effects of polymethylmetnacrylate (PMMA) spacer loaded with different concentrations of vancomycin on the proliferative, osteogenic, and angiogenic capacity of the induced membrane.<bold>Methods: </bold>Varying concentrations of vancomycin (0, 1, 2, 4, 6, 8, and 10 g) were fully mixed with bone cement powder (40 g), resulting in seven experimental groups. Hollow cylindrical PMMA spacers (10 mm height, 3 mm external diameter, and 0.8 mm internal diameter) were formed by a mold and submerged in phosphate-buffered saline for antibiotic release by spectrophotometry. Eighty-four New Zealand white rabbits were evenly randomized into seven groups, and segmental radius shaft defects (10 mm) were created. Defects were filled with cylindrical PMMA spacers containing different vancomycin concentrations, and subsequently underwent intramedullary fixation with a retrograde Kirschner's wire. Tissue toxicity was assessed and the proliferative, osteogenic, and angiogenic capacity of induced membranes were qualitatively analyzed by immunohistochemistry and real-time PCR.<bold>Results: </bold>No obvious toxicity was observed in the animal model. Alizarin red s staining and qualitative detection of type I collagen, CD31, Ki67, and STRO-1 by immunohistochemistry revealed an obvious decrease in the percentage of positively stained cells and in osteogenic capacity when the concentration of vancomycin was more than 6 g per cement dose. Quantitation of gene expression related to osteogenesis (Col1a, Alp, and Runx2), vascularization (Vegf, Tgfb1, and vWF), and proliferation (Oct4 and Stro-1) by real-time PCR revealed slight increases in the expression of selected genes at low vancomycin concentrations (1-4 g per cement dose), and relatively lower gene expression when the concentration of vancomycin was more than 6 g per cement dose.<bold>Conclusion: </bold>PMMA spacers loaded with relatively low concentrations of vancomycin (1-4 g per cement dose) did not interfere with the proliferative, osteogenic, and angiogenic capacity of induced membranes, and even promoted their capacity. In contrast, spacers loaded with relatively high concentrations of vancomycin (6-10 g per cement dose) had negative effects on osteoblast viability, angiogenesis, and proliferation. [ABSTRACT FROM AUTHOR]