ELABORATION OF AN EXPERIMENTAL ANIMAL-MODEL FOR QUANTITATIVE AND QUALITATIVE STUDIES ON REPARATIVE OSTEOGENESIS

This paper describes an experimental animal model employed by us for e valuation of the effects of PEMFs on reparative osteogenesis. The moda lity and extent of reparative osteogenesis were studied in transcortic al holes of equal diameter and depth, drilled at the same levels of di aphyseal and metaphyseal regions of homotypic metacarpal bones of adul t horses. The macroscopic and microscopic observations show that, as u sually happens in membranous ossification, all the holes, regardless o f the level at which they were made, repair by deposition of woven bon e tissue and along two directions: from the endosteum toward the perio steum, and concentrically to the longer axis of the hole. The quantita tive data show that: (1) the amount of bone newly formed in 60 days is very similar in holes made at the same levels of homotypic bones (% = 1.5-3.7); (2) the rate of bone repair is higher in metaphyseal than i n diaphyseal holes; and (3) the rate of bone deposition decreases from the endosteum toward the periosteum. Thus reparative osteogenesis pro ceeds with different biorhythms according to the skeletal region where it takes place, and the endosteum has a more powerful osteogenetic ac tivity than the periosteum. The high reproducibility of the animal mod el described here makes it suitable for studies on electrical stimulat ion of reparative osteogenesis.