Osteogenic capacity of periosteal grafts. A qualitative and quantitative study of membranous and tubular bone periosteum in young rabbits.

A standardized model, permitting only periosteal bone formation, has been applied for qualitative and quantitative studies on the osteogeneses from periosteal grafts. The periosteum from the tibia was grafted to the skull and vice versa. The investigation also included the study of periosteal bone formation combined with other osteogenic factors. A total of 78 operations were performed on the tibias and skulls of 43 growing rabbits. For qualitative studies ordinary histological methods were used. Tibial periosteal grafts to skull defects started bone formation already after 2 weeks and, via a very small amount of woven bone, compact bone and bone marrow was formed after 8-10 weeks. Combined epidural and subperiosteal bone formation gave a calvarial bone. Skull periosteal grafts to tibial defects started bone formation somewhat later, but, after more woven bone as an intermediate stage, the defect had healed with thick compact bone and bone marrow after about the same period. For quantitative studies the newly formed periosteal bone was removed, dry-weighted and ashed. The ashes were dissolved in HCl for spectrophotometric determination of total Ca content, which was used as a quantitative measure of bone amount. Tibial periosteum grafted to a calvarial defect halved its bone forming capacity but compared to the in situ skull periosteal potential, the capacity was tripled. This meant that the defect was completely healed. Calvarial periosteum was much less potent than was the tibial periosteum, when both were grafted to skull defects. However, when transplanted to a long bone defect the former increased its bone forming capacity 5 times compared to its original one as an in situ flap. Environmental functional demands seem to influence the type of bone formation and the final structure of the new bone. On the other hand, there are differences between long and membranous bone periosteum regarding the amount of bone formed.