OBJECTIVEPosterolateral intertransverse process fusion was performed in aged and young adult female rabbits lumbar spine using recombinant human bone morphogenetic protein-2 (rhBMP-2) and autograft to reveal the function of rhBMP-2 on spinal fusion on aged animals.

METHODSA total of 24 female New Zealand white rabbits included 12 young adult of 6 months and 12 aged of 2-year-old, was divided into 4 groups: (1) young adult autologous iliac crest bone group [ICBG(Y), n=6); (2) young adult rhBMP-2/absorbable collagen sponge (ACS) group [BMP-2(Y), n=6]; (3) aged autologous iliac crest bone group [ICBG(O), n=6]; aged rhBMP-2/ACS group [BMP-2(O), n=6]. All were underwent posterolateral fusion in same day. rhBMP-2 and autologous iliac crest bone was implant bilateral LS-L6 intertransverse processes, respectively. Half of the rabbits were sacrificed at 3.6 weeks following surgery, respectively. The results were assessed by manual palpation, radiographs, computed tomographic scans (3D) and histology.

RESULTSSix weeks after surgery, radiography, computed tomography and histology indicated the different result in healing in the posterolateral fusion using rhBMP-2 compared to ICBG (P < 0.05). Aged BMP-2 group showed significantly higher fusion rates than Aged ICBG group.

CONCLUSIONThis study demonstrated rhBMP-2 can increase the posterolateral fusion rate and new bone quality in aged rabbitss than autograft, it may take the place of ICBG. But its role is effected by age.