Navigating diagnostic challenges: E. coli-derived recombinant human bone morphogenetic protein-2 (rhBMP-2) induced endplate osteolysis and delayed spondylodiscitis: a case report.

Background: Escherichia coli (E. coli)-derived recombinant human bone morphogenetic protein-2 (rhBMP-2) (NOVOSIS®, CGbio, Inc., Seoul, Republic of Korea) is increasingly used in selected spinal fusion surgeries to promote bony fusion between vertebrae. Older formulations of rhBMP-2 have been associated with various complications, including vertebral endplate osteolysis, which can complicate the diagnosis and management of postoperative patients. We present the first reported case of vertebral endplate osteolysis associated with E. coli-derived rhBMP-2 using the NOVOSIS® carrier. Case Description: A 54-year-old man who underwent lumbar spinal fusion surgery. Initially treated for delayed onset postsurgical spondylodiscitis, the diagnosis of rhBMP-2 induced vertebral endplate osteolysis was only established after clinical and radiological reassessment. The patient presented with non-specific lower back pain 3 months after surgery. Initial magnetic resonance imaging (MRI) revealed single-level intradiscal fluid with adjacent endplate erosions, mild disc cage subsidence, marrow edema, and a rim-enhancing fluid collection. Biochemical markers were not convincing for spondylodiscitis and blood cultures were negative. Nonetheless, he was treated empirically with oral antibiotics. The patient showed significant improvement 3 weeks after the initial diagnosis was made, with subsequent imaging findings demonstrating the development of endplate osteolysis and implant subsidence. Conclusions: This case demonstrates the difficulty in diagnosing rhBMP-2 induced endplate osteolysis as it mimics spondylodiscitis on imaging. Clinicians should consider this complication as a differential diagnosis to avoid unnecessary antibiotic treatment and to improve postoperative monitoring protocols, even with newer rhBMP-2 formulations.