• Zi Qiang Glen Liau.
• *Department of Orthopaedic Surgery, National University Hospital, Singapore, Singapore †Department of Orthopaedic Surgery, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
• Spine. 2017 Aug 15; 42 (16): E933-E938.

Study DesignWe developed a spinal nerve root wrapping rodent model to evaluate the relationship between recombinant human bone morphogenetic protein 2 (rhBMP-2) dosage and the degree of inflammation.ObjectiveTo investigate the direct effects of recombinant human bone morphogenetic protein 2 (rhBMP-2) dosage and the degree of inflammation in rodent spinal nerve roots.Summary Of Background DatarhBMP-2 is commonly used in clinical practice to augment spinal fusion. However, complications such as postoperative leg pain, and a higher rate of postoperative neurologic deficits have been reported. These may be attributable to the exposure of adjacent nerve roots to high doses of rhBMP-2.MethodsEighteen rats were randomized into three groups as follows: Group 1: absorbable collagen sponge (ACS) + 10 μg rhBMP-2, Group 2: ACS + 1 μg rhBMP-2, and Group 3 ACS with 20 μL saline. The ACS containing rhBMP-2 or saline were then wrapped around the L5 nerve root and secured loosely with nonabsorbable sutures. At 1-week postoperation, the rats were sacrificed, and the L5 nerve root and dorsal root ganglion harvested for reverse transcription polymerase chain reaction (RT-PCR), histology and immunohistochemical staining.ResultsIn our study, 10 μg rhBMP-2 induced a 10-fold increase in seroma compared with 1 μg group. Using RT-PCR, macrophage markers MIP3-α, and CD-68 were upregulated by 8- and 2-fold respectively in comparison with the saline group. Haematoxylin and eosin (H&E) images demonstrated disruption of nerve structures in the high dose 10 μg rhBMP-2, but not at 1 μg rhBMP-2 and with saline.ConclusionHigh doses of rhBMP-2 induced neuroinflammation in a dose dependent manner, resulting in higher seroma volume, macrophage marker gene expressions, and higher proportions of immunohistochemically stained TNF-alpha and more macrophage infiltration.Level Of Evidence2.

11 keywords...

hide…