Biocompatibility and effect on osteogenesis of poly(ortho ester) compared to poly(DL-lactic acid)

Implantation of demineralized bone induces new bone formation by the action of contained growth factors, of which bone morphogenetic proteins are of p rime importance. A biodegradable polymer may be used as a carrier for demin eralized bone particles or recombinant bone growth factors to prevent displ acement of the implant, preserve its volume and shape, and assure sustained release of the incorporated active components. A polymer for this use shou ld be biocompatible and completely absorbed without interfering with the os teogenesis. We investigated the host-tissue response and effect on deminera lized bone-induced bone formation by two biodegradable polymers, a poly(ort ho ester) and an amorphous low-molecular poly(DL-lactic acid). Both polymer s had a plastic consistency, could easily be molded, and adhered well to th e demineralized bone particles. Demineralized bone particles were implanted alone and in combination with each of the polymers in the abdominal muscle s of 45 male Wistar rats. Four weeks after the operation the implants were recovered and subjected to Sr-85 uptake analysis to quantify bone formation and histologic examination. The poly(ortho ester) provoked little inflamma tion; it was largely absorbed by 4 weeks, and no qualitative or quantitativ e effect on bone formation was found. The poly(DL-lactic acid) provoked a c hronic inflammation with multinuclear giant cells, macrophages with engulfe d material, and proliferating fibroblasts; part of the material was still p resent, and the bone formation was inhibited. (C) 2000 John Wiley & Sons, I nc.