INFLUENCE OF DIFFERENT REHYDRATION PERIOD S ON THE STABILITY AND THE WATER-CONTENT OF BONE ALLOGRAFTS AFTER LYOPHILIZATION, GAMMA-IRRADIATION, AND LIPID EXTRACTION

Several studies demonstrated the necessity of rehydration of lyophiliz ed bone allografts prior to implantation. The purpose of the presented study was to evaluate the influence of different rehydration periods on the stability of human cortical lyophilized and gamma-irradiated al lografts, the capability of lyphilized bone for rehydration, as well a s the effects of lipid extraction on rehydration. Breaking strength of lyophilized irradiated cortical bone after different rehydration peri ods (0.5, 1, 2, 4, 8 hours) showed no significant difference. Weight r eduction after lyophilization of human femoral heads was between 7.6% and 41%. Further weight reduction occurred after lipid extraction (38. 7%). Total weight loss was 56.9%. There was a significant influence of intraosseous lipid content on the rehydration capability. After lyoph ilization alone the rehydration weight after 8 hours was only 18.1%, w hereas after lipid extraction the weight increase was 43% after 0.5 ho urs, 36.4% after 1 hour, 57.6% after 2 hours, 60% after 4 hours, and 9 2.7% after 8 hours. Clinical relevance: Based on the presented data re hydration time of 0.5 hours seems to have no disadvantage compared to longer time periods concerning breaking strength. Therefore a longer i ntraoperative time period seems not to be necessary. This is of advant age for a possible secondary contamination while the allograft is rehy drated. Rehydration after lipid extraction is more effective than rehy dration after lyophilization alone. However, the question whether lipi d extraction alter bone stability has to be proved in further studies.