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 evaluation of the effects of PEMFs on reparative osteogenesis. The modality and extent of reparative osteogenesis were studied in transcortical holes of equal diameter and depth, drilled at the same levels of diaphyseal and metaphyseal regions of homotypic metacarpal bones of adult horses. The macroscopic and microscopic observations show that, as usually happens in membranous ossification, all the holes, regardless of the level at which they were made, repair by deposition of woven bone tissue and along two directions: from the endosteum toward the periosteum, and concentrically to the longer axis of the hole. The quantitative 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 in diaphyseal holes; and (3) the rate of bone deposition decreases from the endosteum toward the periosteum. Thus reparative osteogenesis proceeds with different biorhythms according to the skeletal region where it takes place, and the endosteum has a more powerful osteogenetic activity than the periosteum. The high reproducibility of the animal model described here makes it suitable for studies on electrical stimulation of reparative osteogenesis.