[Influences of induced membranes on heterotopic bone formation within an osteo-inductive complex. Experimental study in rabbits]

Based on a new concept, a procedure combining induced membranes and cancellous autografts allows the reconstruction of wide diaphyseal defects. To date, this procedure is limited by the amount of cancellous bone available from the patient and by the related morbidity at the donor site. The aim of this study was to evaluate the biological effect of induced membranes on a cylindrical-shaped ceramic implants loaded with OP-1 in heterotopic site.Sixty hydroxyapatite tricalcium phosphate (HA-TCP) implants, 20 of which being loaded with a bone growth factor (rhOP-1) were inserted either in a subcutaneous tunnel or within a previously induced membrane on the back of rabbits. There were two time-points at four and 16 weeks. Implants were investigated at three different levels (extremities and middle).None of the untreated implants showed any evidence of bone formation. Implants inserted in an induced membrane presented with less resorption. Bone ingrowth within the pores of the materials was significantly higher when the implants were inserted into the induced membrane whatever the time-point considered.The membrane seems to play the role it was assigned, i.e. to protect and revascularize the implant, thus favouring osteogenesis that occurs in 80% of the implants after four months.