[Bone integration within calcium phosphate ceramic by creation of posterior inter-articular lumbar spine fusions in dogs].

Following earlier experiments in which several calcium phosphate ceramics were tested, the aim of this study was to evaluate bone integration within a macroporous biphasic calcium ceramic (M.B.C.P.) in comparison to autologous bone grafts, by producing posterior lumbar spine fusions in dogs. Five dogs were used. 40 posterior lumbar joints were exposed; 38 articular surfaces were removed, 27 M.B.C.P. and 5 autologous bone grafts were implanted; 6 joints were kept free of implant for control purposes. Fixation with a metal rod was performed using Luque's method. Tetracycline was used for a double marking of bone growth. Joints were removed at 4 weeks in 1 dog, 8 weeks in two and 13 weeks in the remaining 2 dogs. Demineralized and non demineralized sections were examined. After 1 month, sections with M.B.C.P. showed early signs of mineralization of the scar tissue between the biomaterial and one of the facets of the joint. Fluoroscopy revealed an absence of bone growth in the pores at the center of the ceramic implant. After 3 months, a number of M.B.C.P. blocks had become integrated into both sides of the joint; however some microfractures in the biomaterial with discontinuity between the mineralized areas was seen. Macroporous calcium phosphate ceramic leads to revascularization allowing bone reconstruction. Similarities in the kinetics and mechanisms of bone integration between the ceramic and autologous bone grafts are demonstrated.