Animal studies of application of rhBMP-2 in maxillofacial reconstruction

A pilot study in adult male Macaca fascicularis (rhesus) monkeys was undertaken to observe the effect of two dose ranges of recombinant human BMP-2 on bone regeneration following bilateral hemimandibulectomies. The mandibulectomies consisted of 2.2 centimeter resections through the entire thickness of the mandible with the remaining bone segments maintained in a distracted position by orthopaedic mesh (TiMesh). In three animals, the dose range on one mandibulectomy site in each animal was 0.8 mg BMP-2 per cc with the contralateral defect receiving 0.2 mg of the rhBMP-2. The carrier was a collagen I sponge (Helistat). These animals were sacrificed at five months postoperatively. In an additional four animals, a dose of 0.4 mg per cc was used on one site with a particulate autogenous graft of cortical cancellous bone used as a control on the contralateral defect. After four months, the reconstructed areas were re-exposed and implanted with root-form Steri-oss implants (Steri-Oss). These implants were brought into occlusion at the end of an additional four month period and are being evaluated for a period of 6 months of function. In all seven animals, the alveolar ridges were regenerated completely with restoration of contour and cortical bone. In the three animals euthanized at five months, histomorphmeic analysis revealed excellent calcified bone matrix to marrow spaces ratios. The result of this work indicates that recombinant human BMP-2 can bring about osseous regeneration of critical sized hemimandibulectomy defects in rhesus monkeys.