Histopathologic inflammatory response induced by recombinant bone morphogenetic protein-2 causing radiculopathy after transforaminal lumbar interbody fusion

Background contextA significant increase in off-label use of recombinant human bone morphogenic protein-2 (rhBMP-2) in posterior lumbar interbody fusion techniques has been seen in the spine community. Numerous reports have demonstrated complications with use of this proinflammatory agent; however, the in vivo response caused by rhBMP-2 has not been characterized on a cellular level.PurposeTo report the case of lumbar radiculopathy and the associated histopathologic findings stemming from the inflammatory response to rhBMP-2 used in transforaminal lumbar interbody fusion (TLIF) surgery.Study design/settingCase report.Patient sampleSingle patient case report of rhBMP-2 off-label use causing an inflammatory response that resulted in radiculopathy after TLIF surgery.Outcomes measuresClinical, radiologic, and histopathologic evidence was used to determine outcomes in this report.MethodsA 27-year-old male presented with low back pain and radiculopathy and radiographic evidence of degenerative disc disease and foraminal stenosis. Four weeks after L4–L5 TLIF surgery augmented with rhBMP-2, the patient developed right-sided lower extremity radiculopathy. Magnetic resonance imaging of the lumbar spine demonstrated bilateral fluid collections with the larger right-sided mass compressing the right L4 nerve root.ResultsSurgical decompression of this mass resulted in resolution of his right-sided radicular symptoms. Histologic analysis of the surgical pathology demonstrated diffuse osteoid and woven bone amidst a fibrovascular stroma densely populated by lymphocytes and eosinophils.ConclusionsOff-label rhBMP-2 use in posterior interbody fusion techniques can lead to complications. This case serves to identify potential hazards of this growth factor and highlight areas for further study to better understand its in vivo behavior.