title: Symptomatic calcified perineural cyst after use of bone morphogenetic protein in transforaminal lumbar interbody fusion: a case report.
abstract: BACKGROUND
  Human recombinant bone morphogenetic protein-2 (BMP-2) is commonly used in spinal surgery to augment arthrodesis, and a number of potential complications have been documented.
  
  
  OBJECTIVE
  To present the case of a delayed radiculopathy that occurred because of a calcified perineural cyst that formed after an L4-L5 transforaminal lumbar interbody fusion (TLIF) in which BMP-2 was used.
  
  
  METHODS
  Case report of a 70-year-old man presented with back and right lower extremity pain.
  
  
  METHODS
  A 70-year-old man who had previously undergone a right L4-L5 TLIF presented 20 months after surgery with progressively radiating right leg pain. Imaging revealed a right-sided L4-L5 cystic lesion posterior to the interbody cage. The patient underwent reexploration, and a calcified mass was discovered.
  
  
  RESULTS
  Histopathology revealed fragments of organized collagenous connective tissue, new collagen, and partially calcified fragments of fibrocartilage, bone, and ligament.
  
  
  CONCLUSIONS
  This is the first reported case of a symptomatic calcified perineural cyst developing after a fusion procedure in which BMP-2 was used. The presence of connective tissue with metaplastic bone formation and maturation within the lesion suggests that formation of the cyst was secondary to application of BMP-2, as it possesses both osteogenic and chondrogenic capabilities.
authors.affiliation: Department of Neurosurgery, University of Michigan Health System, 1500 E. Medical Center Drive, Ann Arbor, MI 48109-5338, USA.
authors.forename: Khoi D
authors.initials: KD
authors.lastname: Than
authors.forename: Shayan U
authors.initials: SU
authors.lastname: Rahman
authors.forename: Paul E
authors.initials: PE
authors.lastname: McKeever
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Wang
authors.forename: Frank
authors.initials: F
authors.lastname: La Marca
authors.forename: Paul
authors.initials: P
authors.lastname: Park
mesh_terms: D000368:Aged; D019485:Bone Morphogenetic Proteins / Q000009:adverse effects* / Q000627:therapeutic use; D006801:Humans; D008159:Lumbar Vertebrae / Q000473:pathology / Q000601:surgery*; D008297:Male; D011843:Radiculopathy / Q000209:etiology* / Q000473:pathology / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation; D052958:Tarlov Cysts / Q000209:etiology* / Q000473:pathology / Q000601:surgery
chemical_list: D019485:Bone Morphogenetic Proteins
keywords: Bone morphogenetic protein; Perineural cyst; Transforaminal lumbar interbody fusion