title: Efficacy of osteogenic protein-1 in a challenging multilevel fusion model.
abstract: METHODS
  A therapeutic study compared the influence of osteogenic protein-1 to autograft and collagen carrier in multilevel sheep spine fusions.
  
  
  OBJECTIVE
  To evaluate the efficacy of osteogenic protein-1 compared to autograft and collagen carrier in achieving fusion in a challenging multilevel lumbar spine ovine model.
  
  
  BACKGROUND
  Bone morphogenetic proteins can successfully augment spinal fusion. To date, all the preclinical and clinical studies using bone morphogenetic proteins have evaluated single-level fusion. In practice, multiple level fusions are commonly required for various conditions, like spinal deformity.
  
  
  METHODS
  Eighteen sheep underwent three-level spine fusion. Six sheep were treated with osteogenic protein-1 and its carrier, autograft, or with the carrier alone. Specimens were analyzed for evidence of fusion by palpation, radiographic and histologic analysis, and biomechanical testing.
  
  
  RESULTS
  Manual palpation testing for the presence of fusion showed none of the specimens fused all three levels or fused at the lumbosacral junction. No statistically significant difference was found between the osteogenic protein-1 and autograft groups' fusion rates based on radiographic grading (P = 0.65) or biomechanical testing. Histologic analysis showed no qualitative difference in bone morphology or cellularity of fusion masses when comparing the autograft and osteogenic protein-1 specimens.
  
  
  CONCLUSIONS
  No model before this exists that tests the efficacy of bone morphogenic proteins in as challenging an environment. Extrapolation of single-level preclinical and clinical studies with bone morphogenic proteins for use in multilevel fusion requires careful review. Autograft and osteogenic protein-1 had similar rates of fusion. A high rate of nonunion is seen with this multiple level fusion to the sacrum using autograft or osteogenic protein-1. The biologic enhancement with osteogenic protein-1 is not able to overcome this mechanically rigorous model.
authors.affiliation: Department of Orthopaedic Surgery, University of California, Davis, Sacramento 95817, USA. mermerm@hss.edu
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Mermer
authors.forename: Munish C
authors.initials: MC
authors.lastname: Gupta
authors.forename: Donna L
authors.initials: DL
authors.lastname: Wheeler
authors.forename: Joel
authors.initials: J
authors.lastname: Helgerson
authors.forename: A Hari
authors.initials: AH
authors.lastname: Reddi
authors.forename: Scott
authors.initials: S
authors.lastname: Hazelwood
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Benson
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000627:therapeutic use*; D016025:Bone Transplantation; D005260:Female; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D011859:Radiography; D012756:Sheep; D013123:Spinal Fusion / Q000379:methods*; D016212:Transforming Growth Factor beta / Q000627:therapeutic use*
chemical_list: D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta