Use of a phosphophoryn-Ca(+2)-collagen composition that mimics a mineralization front in unicortical defects in long bones.

The present study was designed to ascertain if dynamic ionic matrices that mimic the mineralization front could be used as active scaffolds for bone repair. Dentinal phosphophoryn calcium salts were extracted from unerupted bovine dentine using chatopic buffers and EDTA. The phosphophoryns were subsequently isolated following precipitation with CaCl2. The phosphophoryn-Ca+2 salts were then mixed with pepsin solubilized bovine skin collagen and lyophilized into hardened sponges. Three groups of 4 beagle dogs were employed such that one leg served as an experimental test site for a mechanical wound, while the contralateral leg served as a control. Animals were sacrificed at 1,3, and 6 month intervals. The test specimens were harvested, fixed, and processed for routine histology, examined with image histomorphometric analysis, and scored. Tabulation of these data indicated that phosphophoryn-Ca(+2)-collagen enhances the repair of mechanically formed osseous defects in the distal femur of beagle dogs. This enhanced rate of bone repair was manifest by earlier filling of bony voids with osteoid and trabecular bone. Eventually, this process was followed by recortification of the surface defects. These data suggest that components derived from a mineralization front may influence bone formation in unicortical defects within long bones.