Ingrowth of bone into absorbable bone cement: an in vivo microscopic evaluation

The purpose of the study reported here was to use an in vivo rabbit model to evaluate the rate of bone ingrowth into remodelable calcium phosphate bone cement. We evaluated an in vivo bone chamber placed in a rabbit tibia with its ingrowth compartment filled with absorbable calcium phosphate bone cement (Norian Skeletal Repair System; Norian Corp, Cupertino, Calif). Five New England white rabbits had a single bone chamber implanted into the proximal right tibia. Observations were made and photomicrographs taken on a weekly basis. Results of morphological analysis showed sequential loss of cement and subsequent bone ingrowth over a testing period of up to 30 weeks. Resorption of bone cement was complete in 1 rabbit. The other rabbits had significant bone ingrowth, which reaffirms the biocompatibility of this material. Results of this study showed that using in vivo microscopy with the rabbit bone chamber model was useful in evaluating bone ingrowth and replacement of absorbable bone cement. This model may make it possible to evaluate various combinations of bone cement and bone growth factors, which could serve as an alternative to autogenous bone grafting.