Use of recombinant human bone morphogenetic protein-2 as an adjunct for instrumented posterior arthrodesis in the occipital cervical region: An analysis of safety, efficacy, and dosing

BACKGROUND: There have been few reports on the use of recombinant human bone morphogenetic protein (rhBMP)-2 in posterior spine. However, no study has investigated the dosing, safety, and efficacy of its use in the posterior atlantoaxial, and/or craniovertebral junction. Recent case report of the cytokine-mediated inflammatory reaction, following off label use of rhBMP-2 as an adjunct for cervical fusion, particularly in complex cases, has increased concern about complications associated with the product. OBJECTIVE: To assess the safety, efficacy, and dosing of rhBMP-2 as an adjunct for instrumented posterior atlantoaxial and/or craniovertebral junction arthrodesis. MATERIALS AND METHODS: We included all patients treated by the senior author that included posterior atlantoaxial and/or craniovertebral junction instrumented fusion using rhBMP-2 from 2003 to 2008 with a minimum two year follow-up. Diagnosis, levels fused, rhBMP-2 dose, complications, and fusion were assessed. RESULTS: Twenty three patients with a mean age of 60.9 years (range 4 - 89 years) and an average follow-up of 45 months (range 27 to 84 months) met inclusion criteria. The indications for surgery included, atlantoaxial instability (n = 16), basilar invagination (n = 6), and kyphoscoliosis (n = 1). The specific pathologic diagnosis included type 2 dens fracture (n = 7), complex C1 and C2 ring fracture (n = 2), chordoma (n = 2), degenerative/osteoporosis (n = 3), rheumatoid disease (n = 8), and pseudogout (n = 1). The average rhBMP-2 dose was 2.38 mg/level, with a total of 76 levels treated (average 3.3 levels, SD= 1.4 levels). There were no complications. During the most recent follow-up, all patients had achieved fusion. CONCLUSIONS: In a series of patients with complex pathology and/or rheumatoid arthritis, 100% fusion rate was achieved with adjunct use of rhBMP-2, with a safe and effective average rhBMP-2 dose of 2.38 mg per level.