Experimental Model for the Study of Osteogenesis and Remodeling

The experimental model in this study yielded a consistent pattern of normal healing. Thus, it is useful in studies of the effects of various extrinsic and intrinsic factors on osteogenesis and remodeling. Incorporation of the callus with the cortex appeared to involve the creation of new osteon formed partly by the callus and partly by the orig-inal bone. The majority of experimental studies on bone healing have used complete displaced fractures as models.'-5 Although these models have yielded considerable informa-tion, they are limited because of the vari-ability of the healing process. In attempting to study factors (intrinsic or extrinsic) that might affect osteogenesis or remodeling, we found that this variability in the healing of displaced fractures in animals was so great that it made precise determination of the effect of any experimental maneuver diffi-cult.6 For this reason, we studied the con-sistency of healing of a bone defect that involved only the cortex. This type of a bone wound eliminates the variables of fracture size, degree of displacement, and amount of bone and soft tissue damage. The healing of this standard experimental model, including the incorporation and remodeling of the callus into the cortical bone, was studied. Materials and Methods Seventy male New Zealand rabbits were used. They weighed an average of 2.0 kg each and were approximately three months of age. They were housed in separate cage