Lipid extracted bank bone. Bone conductive and mechanical properties.

Lipid extraction by chloroform methanol previously has been found to increase the incorporation of frozen bone allografts. This effect may be because of a decreased immunologic response. In the present study, the ingrowth capacity into a grafted bone defect was investigated by using the bone harvest chamber model in rabbits. In a series of experiments, defatted and frozen allografts were compared at 1, 2, and 3 weeks; defatted allografts and defatted autografts were compared at 3 weeks; and frozen or defatted allografts and nongrafted defects were compared at 3 weeks. Evaluation was performed through histology, histomorphometry, and 99mTc-MDP scintimetry. The incorporation was better with defatted grafts: by histology at 1 week, mesenchymal tissue filled the intertrabecular space in defatted specimens and new bone formation started to occur. In contrast, frozen specimens showed a central soft tissue necrosis surrounded by inflammatory cells. Histomorphometry showed more new bone and more graft resorption in defatted allografts. At 2 and 3 weeks, there was no significant difference in new bone area, but at 3 weeks the scintimetric activity was higher in defatted allografts, probably caused by an increased remodeling rate. Since defatting did not cause increased scintimetric activity in previous autograft studies, these findings could indicate that there is a detrimental immunologic influence on frozen allografts. There were no differences between defatted autografts and allografts. In a second experiment, the biomechanical properties of defatted bone were investigated with a compression test on defatted and frozen bone cylinders taken from the calf femoral neck. No difference in biomechanical properties was found. It was concluded that lipid extraction produced a graft that was better incorporated than a nondefatted graft, with no loss of mechanical function.