Bone morphogenetic protein-induced inflammatory cyst formation after lumbar fusion causing nerve root compression

Area of Science:

• Spinal surgery
• Biomaterials in orthopedics
• Neuro-oncology

Background:

• Bone morphogenetic protein (BMP) is widely used in spinal fusion surgery to promote bone healing.
• While effective, BMP has been associated with various complications, including inflammation and ectopic bone formation.
• Inflammatory cyst formation around BMP implants is a less common but significant complication.

Observation:

• A case report details a 70-year-old woman who developed recurrent radiculopathy six weeks after a minimally invasive transforaminal lumbar interbody fusion using BMP.
• Imaging revealed an intraspinal cyst compressing the L4-L5 nerve roots.
• Surgical reexploration identified an inflammatory fibroblastic cyst originating from the BMP sponge within the interbody cage.

Findings:

• The cyst was successfully decompressed, and the BMP sponge was removed.
• Histological examination confirmed an inflammatory fibroblastic cyst.
• Postoperatively, the patient's radiculopathy resolved, and successful interbody fusion was achieved.

Implications:

• This case highlights inflammatory cyst formation as a potential complication of BMP use in lumbar fusion.
• Spine surgeons should maintain a high index of suspicion for BMP-related inflammatory cysts in patients presenting with delayed neurological deficits.
• Awareness of this complication is crucial for accurate diagnosis and timely management to prevent permanent neurological damage.