Weight-bearing porous fiber titanium implants in rat tibia: a restricted growth model for comparison of normal and pathological bone repair

An experimental model in rats for comparison of bone repair under normal and pathological conditions is described. The low cost of rats and the simple surgical procedure used allow large-scale studies. Although clinical implications must be interpreted with care, our model may prove useful in the attempt to understand how various drugs and metabolic disorders may affect bone healing. We used porous fiber titanium implants to replace a segment of the right proximal tibia in rats. The void space to be filled with bone represented a known and constant volume allowing a direct comparison between differently treated groups. Selected parameters for bone ingrowth could be expressed in terms of growth curves as a function of time, using a mathematical equation for restricted growth. The following parameters for quantity and quality of the ingrown bone were monitored: micromoles calcium as parameter for amount; calcium/hydroxyproline molar ratio for extent of mineralization; calcium/phosphorus molar ratio for maturity of minerals; and ultimate bending stress for strength of the bone-implant interface. With this model we have studied the effect that cis-platinum, an anticancer drug that is used in the treatment of osteogenic sarcoma, has on bone repair.