Porous ceramics as a bone substitute in the medial condyle of the tibia: An experimental study in sheep. Long-term observations

Abstract

Porous ceramic meterial, with a pore size of 100-1000.mu. was implanted in the medial tibial condyle of 6 female sheep from 45-60 kg. in weight and 6-8 yr of age. Epiphyseal fusion had occurred. Ten months postoperatively, 3 animals were sacrificed and in the remaining 2 (1 had already died), the operated knee was X-rayed at 10 mo. The AO-finger plate was then removed and the animals resumed their normal acttivities for 2 mo. before sacrifice. In 2 animals observed for a 12 mo. period, the plate used to stabilize the implant was removed after 10 mo. The implant to the adjacent bone was studied macroscopically, radiographically, microradiographically and by transmitted light microscopy. Bony tissue ingrowth bound all implants to the adjacent bone. The maximum depth of the bone invasion, 3-4 mm., was slightly greater than that observed at 3 mo. Ossification signs were still seen within the pores and bone bridges, between implants and surrounding bone and were particularly well developed in regions of maximal stress. This indicated active adaptation to the actual stress to which the shearing surfaces were exposed. The data justify the use of porous ceramic implants for clinical trial in man.