Abstract

The purpose of this study was to evaluate the influence of age on the effectiveness of rhBMP-7 treatment in a fracture with severe periosteal damage that is known to result in non-union formation. Closed stabilized femur fractures were produced in 3-month-old and 18-month-old rats. The fracture site was exposed and 2 mm of the periosteum cauterized circumferentially to impair normal fracture healing. The cauterized fracture site was immediately treated with either 100 mg rhBMP-7 (BMP-7 group), or with 25 xL of vehicle alone (control group). Fracture healing was evaluated with radiographs taken at 3 and 6 weeks. Animals were sacrificed at 3 and 6 weeks and specimens subjected to biomechanical and histological evaluation. In both age groups, none of the control animals healed throughout the 6 weeks experimental duration. All of the rhBMP-7–treated 3-month-old animals were radiographically healed at 3 weeks. In comparison, only 56% (9/16) of the rhBMP-7–treated 18-month-old animals were radiographically healed at 3 weeks. At 6 weeks, however, all of the 18-month-old rhBMP-7–treated animals had healed. Histology revealed slower healing in the 18month-old animals. Treatment with rhBMP-7 significantly increased all of the biomechanical properties in both age groups. In the 3-month-old animals the mechanical strength approached that of the intact femur at 3 weeks, while in the 18-month-old animals this did not occur until 6 weeks. In conclusion, rhBMP-7 can effectively stimulate fracture repair in both young (3-month-old) and old (18-month-old) rats. However, the effect of rhBMP-7 on the rate of fracture healing is greater in young rats compared to old rats.

Disciplines

Biomedical Engineering and Bioengineering

Publisher statement

This is the pre-peer reviewed version of the following article: Recombinant Human BMP-7 Effectively Prevents Non-Union in Both Young and Old Rats, Scott J. Hazelwood, Journal of Orthopaedic Research, 24:1.

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URL: https://digitalcommons.calpoly.edu/bmed_fac/48