Retrospective Study of Posterior Cervical Fusions With rhBMP-2

Abstract

Posterior cervical decompression and fusion can be performed for various spinal conditions. Previous rates of pseudoarthrosis have been reported in up to 38% of patients. The use of bone morphogenic protein (BMP) has been approved for use in certain anterior lumbar interbody fusion techniques to decrease the incidence of pseudoarthrosis. Bone morphogenic protein in the anterior cervical spine carries a potential increased risk of airway complications; however, few data exist on the safety and efficacy of BMP in the posterior cervical spine. The purpose of this study was to evaluate fusion success, safety, and heterotopic bone formation using BMP in posterior cervical fusion.Twenty-nine patients who received posterior cervical fusion with BMP were followed for a minimum of 12 months. Computed tomography scans were obtained at a minimum of 12 months postoperatively to evaluate for solid arthrodesis and the presence of heterotopic bone formation. Patients' demographic data and adverse events were evaluated. All patients underwent posterior cervical decompression and instrumented fusion of at least 1 level between 2006 and 2008. Of 37 patients eligible for the study, 29 agreed to participate. Three (10.3%) of 29 patients developed pseudoarthrosis, as found on computed tomography scan. None of these went on to further surgery. No evidence existed of heterotopic bone formation outside of the lateral masses or bone growth over the spinal canal or neuroforamen. No adverse events were related to the use of BMP in this series of posterior cervical fusions. Bone morphogenic protein can be used safely in posterior cervical spine fusion, but additional larger studies are recommended. Even with the use of bone morphogenic protein, the possibility of pseudoarthrosis exists.

Reoperation rates for symptomatic nonunions in posterior cervicothoracic fusions with and without bone morphogenetic protein in a cohort of 450 patients

“…5,[7][8][9]50 Very little has been written on fusion rates in posterior cervical spine using BMP. 4,14,23,25,33,53 The study by Xu et al 53 was one of the first on BMP in the subaxial cervical spine, and involved a retrospective review of 48 patients with BMP and 156 patients without BMP. These authors used radiographic studies with more than 6 months of follow-up.…”

“…1,19,39 A few studies have advocated for its use in the posterior cervical spine because of its high fusion rates. 4,14,23,25,33,53 For almost all of the studies on BMP fusion rates, the definition of nonunion has been based solely on radiographic studies. Several studies, 9,13,17,27,44 however, have shown that radiographic nonunions do not necessarily translate into symptomatic nonunions.…”

Reoperation rates for symptomatic nonunions in posterior cervical (subaxial) fusions with and without bone morphogenetic protein in a cohort of 1158 patients

“…Overall, however, there was no significant difference in the total operative nonunions between the groups. Hodges et al 22 prospectively followed 29 patients with posterior subaxial fusions during 12 months with BMP. CT scans were obtained at a minimum of 12 months postoperatively and were evaluated by a neuroradiologist for solid arthrodesis.…”

“…Xu et al 47 indicated that the time to nonunion in the posterior cervical spine was greater than 6 months. Hodges et al 22 evaluated his patients for nonunion at a minimum of 12 months postoperatively. To account for time-to-event, it was helpful to use the Kaplan-Meier curves.…”

“…4,13,20,22,30,47 Controversy surrounding its use has also increased over the years 17,36 with several studies reporting complications 3,8,10,27,35,[39][40][41]45,46,48 and the FDA issuing a safety alert for the off-label use of BMP in the cervical spine in July 2008. 42 One of the justifications for the use of BMP has been the cost savings associated with prevention of fusion failures.…”