Human demineralized freeze-dried bone: inadequate induced bone formation in athymic mice. A preliminary report

The purpose of this study was to test the osteoinductive properties of demineralized freeze-dried bone (DFDBA) randomly purchased from four commercial bone banks. Twenty-five (25) milligrams of bone from each of the banks was implanted into the hindquarter muscles of athymic mice. Two samples from each of the banks were compared with samples from the other banks. A total of 16 implants were grafted into 8 mice. Two additional mice served as controls. One mouse received an implantation of deactived human cortical bone matrix (DBM) (negative control). The other mouse received an implant of human bone morphogenetic protein/non-collagenous proteins (hBMP/NCP) infused to surface demineralized human cortical bone (positive control). At 21 days the mice were killed, the hindquarters were photographed, and the tissues were prepared for histologic evaluation. Of the 16 commercial DFDBA implants, 12 were available for histologic evaluation. There was no radiographic evidence of bone formation for the DFDBA implanted mice or the DBM implants. Small bone ossicles were scarcely visible in the hindquarters of the mouse which received the hBMP/NCP infused bone. Histomorphometric analysis was used to determine the percentage of new and dead bone. The bone was measured in pixels. The predominant histologic feature of the DFDBA implants was non-vital bone chips with minimal amounts of new bone. The average amount of non-vital bone ranged from 78.4% to 92.5%. There was no evidence of bone formation for the DBM implants. The average amount of bone for the mouse which received hBMP/NCP was 96%. The results of this pilot study indicate that commercially-available DFDBA induced clinically insignificant amounts of bone.(ABSTRACT TRUNCATED AT 250 WORDS)