Hydroxyapatite granule graft combined with recombinant human bone morphogenic protein-2 for solid lumbar fusion.

The purpose of this study was to evaluate the availability of recombinant human bone morphogenetic protein-2 (rhBMP-2) combined with hydroxyapatite (HA) and autogenous bone. Posterolateral intertransverse fusion between the fifth and sixth lumbar vertebrae was performed in 27 adult Japanese white rabbits. These 27 rabbits were classified into three groups: the autogenous bone group, the HA group, and the bone morphogenic protein (BMP) group. In the HA group, HA (0.5 g) mixed with iliac bone was grafted. In the BMP group, HA (0.5 g) soaked with rhBMP-2 (100 mg) and iliac bone was grafted. At 6 weeks after the procedure, bone union was evaluated. In the BMP group, all cases showed solid bone union, and fusion masses were stiffer than the masses obtained in the other group. Biomechanically and histologically, grafts of HA soaked with rhBMP-2 and iliac bone was clearly effective in obtaining a solid intertransverse arthrodesis.