Comparison of segmental fracture healing in young and old rats that were treated with bone stimulators - biomed 2009.

Demineralized bone matrix (DBM) has been shown to have osteoinductive properties, and demonstrated accelerated rate of bone regeneration. However, prior studies using DBM in young rats have not been consistent with results witnessed in an older rat population. There were two aims of this study: (1) to compare segmental bone defect healing in old rats treated with DBM versus young rats treated with DBM over time, and (2) to compare the number of cell types present at the fracture site in young and old animals during fracture repair. DBM was delivered over time with an initial burst of substances and subsequent sustained release over time using the calcined tricalcium phosphate lysine (TCPL) capsules. In addition, the capsules contained antibiotics to prevent infection. The fracture sites were evaluated for evidence of fracture healing by radiographs and histomorphometric techniques after 4, 8, and 15 weeks. Animals treated with DBM had smaller fracture callus and mature bone present with similar number of osteoblast as control at 15 weeks; whereas animals treated with antibiotic alone had limited bone formation with time. Further studies are needed to investigate the mechanisms leading to bone formation in the presence of growth promoting factors.