Heterotopic induction of osteogenesis in the course of neural injury

Encountered in orthopedics cases of accelerated bone union and abundant formation of the callus in patients after craniocerebral injuries as well as cases of extraskeletal ossification in neural diseases give rise to a question whether neural damage affects in any way the course of osteogenesis. The present study was carried out in an attempt to answer this question in an animal model. The study included 120 inbred WAG rats in which heterotopic induction of osteogenesis was performed by intramuscular placement of decalcified and lyophilized implants of rat cortical bones. By producing various neural damages their effect on the course of osteogenesis was evaluated. The rats were divided into four groups of 30 subjects each. In group I cerebral cortical damage was induced by intracortical injection of kainic acid solution, in group II paraplegia was produced by transverse dissection of the spinal cord on the level of Th 10-11, in group III denervation of the hind limb was performed by dissection of all supplying peripheral nerves, group IV consisted of controls. An attempt was made to evaluate changes in the course of osteogenesis while observing advancing with the passage of time changes in histological patterns of the preparations obtained from the site of bone implantation at 3, 5, 10, 20 and 40 days after the operation. While analyzing the histological pattern I paid attention to features characteristic for the process of osteogenesis such as: formation of granulation around bone grafts, penetration of mesenchymal cells into transplants, differentiation of mesenchymal cells into osteogenic cells, formation of bone tissue and development of bone marrow. The rate of development of these features in the consecutive preparations reflected the dynamics of induced osteogenesis. Analysis of the results showed that experimentally induced neural damage affects the course of osteogenesis. In case of cerebral cortical injury and peripheral neurotomy the formation of granulation around bone grafts was very abundant, whereas penetration of mesenchymal cells into the implants and differentiation of mesenchymal cells into chondroblasts occurred more rapidly than in other animal groups. In contrast, spinal cord injury resulted in a markedly decreased dynamics of osteogenesis which was manifested by weaker cell reaction around the implants and delayed differentiation of mesenchymal cells into chondroblasts. The effect was seen on the 20th day. In the final stage of the study--at 40 days--the effect of neural damage on the course of osteogenesis was reduced and the histological pattern was similar in all animal groups.(ABSTRACT TRUNCATED AT 400 WORDS)