Bone morphogenetic protein (RhBMP-2) as a substitute for iliac crest bone graft in multilevel adult spinal deformity surgery: minimum two-year evaluation of fusion

Abstract

Study design: Prospective, single center, nonblinded radiographic analysis of anterior and posterior adult spinal deformity fusions performed with bone morphogenetic protein (rhBMP-2).

Objective: To determine the ability of rhBMP-2 to achieve multilevel spinal fusion in the deformity patient.

Summary of background data: No previous study has evaluated rhBMP-2 for multilevel adult spinal deformity fusion with 2-year results. We postulated fusion could be achieved without distant autogenous graft harvest.

Methods: Prospective analysis was performed for 98 patients (308 levels; mean age, 51.4 years) who underwent multilevel anterior or posterior spinal fusion (PSF) with minimum 2-year follow-up (average, 2.6 years). Group 1 (10 mg/level) contained 47 patients (109 levels; 2.33 levels/patient) who underwent anterior spinal fusion (ASF): BMP on an absorbable collagen sponge (ACS) with a titanium mesh cage. Group 2 (20 mg/level) included 43 patients (156 levels; 3.63 levels/patient) with PSF: BMP on an ACS with local bone graft (LBG) and bulking agent [tricalcium phosphate/hydroxyapatite (TCP-HA)]. Group 3 (40 mg/level) contained 8 patients (43 levels; 5.38 levels/patient) with PSF: rhBMP-2 and TCP-HA with no autologous bone. Confounding negative factors were present in the study population: medical comorbidities (26%), tobacco use (17%), revision surgery (34%), previous laminectomy (51%), and preoperative pseudarthrosis (27%). Postoperative films (AP, lateral, oblique) were evaluated by independent observers. Average fusion grade was based on a published scale.

Results: Overall fusion rate was 95%. (group 1 91%, group 2 97%, group 3 100%). No confounding factor demonstrated a detrimental statistical significance to fusion.

Conclusion: In multilevel ASF, BMP (10 mg/level) generates fusion without autogenous bone. In multilevel PSF, BMP (20 mg/level) with LBG and TCP-HA produced fusion. BMP (40 mg/level) and TCP-HA without LBG achieved fusion. In multilevel spinal fusion, rhBMP-2 eliminated the necessity for iliac crest bone graft and yielded an excellent fusion rate.