title: Radiographic assessment of interbody fusion using recombinant human bone morphogenetic protein type 2.
abstract: METHODS
  A prospective randomized study investigated the radiographic progress of fusion at 6, 12, and 24 months in 42 patients who underwent a single-level anterior lumbar interbody fusion using cylindrical interbody fusion cages.
  
  
  OBJECTIVE
  To determine the patterns and rates of osteoinduction associated with the use of recombinant human bone morphogenetic protein type 2 (rhBMP-2) and an absorbable collagen sponge carrier in anterior lumbar interbody fusion with a tapered cylindrical fusion device.
  
  
  BACKGROUND
  Studies have shown that rhBMP-2 used with allograft dowels increases the rate of interbody fusion by promoting osteoinduction and enhancing incorporation of the allograft. In a small series of human patients undergoing anterior lumbar interbody fusion with a tapered cylindrical fusion cage, rhBMP-2 has been shown to promote osteoinduction and fusion.
  
  
  METHODS
  In this prospective nonblinded study, 42 patients were randomly divided into two groups. The investigational group underwent interbody fusion using two tapered cylindrical fusion cages (LT-CAGE) and rhBMP-2 on an absorbable collagen sponge, and a control group underwent the procedure, receiving the devices and autogenous iliac crest bone graft. Plain radiographs and computed tomographic scans were used to evaluate the pattern of osteoinduction in the interbody space and the progression of fusion 6, 12, and 24 months after surgery.
  
  
  RESULTS
  All the patients who received rhBMP-2 showed radiographic evidence of osteoinduction in the interbody cages 6 months after surgery. The density in the cages had increased an average of 142 Hounsfield units by 6 months. At 12 months, the increase had reached 228.7 Hounsfield units New bone formation occurred in the disc space outside the cages by 6 months in 18 of the patients in the investigational group (18/22; 82%). By 24 months, all the investigational patients showed new formation outside the cages. In the autograft control group, the density in the cages increased an average of 42 Hounsfield units, and 10 patients (10/20; 50%) showed evidence of bone formation outside the cages.
  
  
  CONCLUSIONS
  The use of rhBMP-2 is a promising method for facilitating anterior intervertebral spinal fusion in patients who have undergone anterior lumbar fusion surgery.
authors.affiliation: Hughston Clinic, PC, Columbus, Georgia 31908-9517, USA. jkb66@knology.net
authors.forename: J Kenneth
authors.initials: JK
authors.lastname: Burkus
authors.forename: John D
authors.initials: JD
authors.lastname: Dorchak
authors.forename: D Lynn
authors.initials: DL
authors.lastname: Sanders
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015519:Bone Density / Q000187:drug effects; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000627:therapeutic use*; D005500:Follow-Up Studies; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008875:Middle Aged; D010012:Osteogenesis / Q000187:drug effects; D011446:Prospective Studies; D011994:Recombinant Proteins / Q000627:therapeutic use; D013123:Spinal Fusion / Q000379:methods*; D013128:Spinal Osteophytosis / Q000000981:diagnostic imaging / Q000601:surgery; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016212:Transforming Growth Factor beta
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2