Evaluation of HealosMP52 osteoinductive bone graft for instrumented lumbar intertransverse process fusion in sheep.

STUDY DESIGN: HealosMP52 was evaluated in a sheep model of instrumented lumbar intertransverse process spine fusion and compared to autogenous bone graft. OBJECTIVES: To determine the long-term efficacy and safety of HealosMP52 as a bone graft substitute in posterolateral instrumented spinal fusion. SUMMARY OF BACKGROUND DATA: Although the standard intertransverse fusion method employs autogenous iliac crest bone, autograft has certain limitations. HealosMP52, an osteoinductive bone graft material, can facilitate noninstrumented posterolateral spine fusion in rabbits and nonhuman primates, but the long-term outcome of such fusions has not been evaluated. METHODS: Eleven skeletally mature, female sheep were instrumented with pedicle screws and rods at L2-L3 and L5-L6. Each animal was treated with autograft bone at one fusion level and HealosMP52 at the other. At 6 and 12 months after surgery, bone formation was measured on contact microradiographs and by backscattered electron imaging. Bone core biopsies taken from 6-month and 12-month specimens were evaluated histologically for pathology indicative of osteosarcoma. RESULTS: Grossly, all autograft- and HealosMP52-treated levels showed stable fusions at 6 and 12 months. HealosMP52 and autograft treatments resulted in equivalent mean percent bone volumes within fusion bodies; similar values were observed at 6 and 12 months. Fusion bodies contained cortical and trabecular bone with osteoid seams and fatty marrow, and fusion masses showed maturation from 6 to 12 months. HealosMP52 treatment was not associated with implant migration, ectopic bone formation, or pathologic abnormality. No histologic evidence of osteosarcoma was seen on bone core biopsies. CONCLUSIONS: This long-term assessment of the use of HealosMP52 in posterolateral instrumented spine fusion indicates that HealosMP52 possesses safe and efficacious bone grafting properties and can potentially serve as anosteoinductive alternative to autograft bone.