title: Graft resorption with the use of bone morphogenetic protein: lessons from anterior lumbar interbody fusion using femoral ring allografts and recombinant human bone morphogenetic protein-2.
abstract: METHODS
  This is a prospective cohort study examining the results and radiographic characteristics of anterior lumbar interbody fusion (ALIF) using femoral ring allografts (FRAs) and recombinant human bone morphogenetic protein-2 (rhBMP-2). This was compared to a historical control ALIF using FRAs with autologous iliac crest bone graft (ICBG).
  
  
  OBJECTIVE
  To determine whether the use of rhBMP-2 can enhance fusion ALIF with stand-alone FRAs.
  
  
  BACKGROUND
  ALIF is a well-accepted procedure in reconstructive spine surgery. Advances in spinal surgery have produced a multitude of anterior interbody implants. The rhBMP-2 has promoted fusion in patients undergoing ALIF with cages and threaded allograft dowels. The FRA still remains a traditional alternative for anterior support. However, as a stand-alone device, the FRA has fallen into disfavor because of high rates of pseudarthrosis. With the advent of rhBMP-2, the FRA may be more attractive because of its simplicity and remodeling potential. It is important to understand the implications when rhBMP-2 is used with such structural allografts.
  
  
  METHODS
  A total of 36 consecutive patients who underwent ALIF with stand-alone FRAs by a single surgeon (E.G.D.) at 1 institute were included. A cohort of 9 consecutive patients who received FRAs filled with rhBMP-2 was followed prospectively. After noticing suboptimal results, the senior author terminated this method of lumbar fusion. A total of 27 prior consecutive patients who received FRAs filled with autogenous ICBG were used for comparison. Analyzing sequential radiographs, flexion-extension radiographs, and computerized tomography with multiplanar reconstructions determined nonunions. Minimum follow-up was 24 months.
  
  
  RESULTS
  Pseudarthrosis was identified in 10 of 27 (36%) patients who underwent stand-alone ALIF with FRAs and ICBG. Nonunion rate was higher among patients who received FRAs with rhBMP-2 (i.e., 5 of 9 [56%]). Statistical significance was not established because of the early termination of the treatment group (P > 0.3). Of interest, radiographs and computerized tomography revealed early and aggressive resorption of the FRAs when used with rhBMP-2. This preceded graft fracture and even disintegration, resulting in instability and eventual nonunion.
  
  
  CONCLUSIONS
  The use of rhBMP-2 did not enhance the fusion rate in stand-alone ALIF with FRAs. In fact, the trend was toward a higher nonunion rate with rhBMP-2, although this was not significant with the numbers available. This result appears to be caused by the aggressive resorptive phase of allograft incorporation, which occurs before the osteoinduction phase.
authors.affiliation: Spine Research Foundation, The Spine Institute at Saint John's Health Center, Santa Monica, CA 90404, USA. benpradhan@yahoo.com
authors.forename: Ben B
authors.initials: BB
authors.lastname: Pradhan
authors.forename: Hyun W
authors.initials: HW
authors.lastname: Bae
authors.forename: Edgar G
authors.initials: EG
authors.lastname: Dawson
authors.forename: Vikas V
authors.initials: VV
authors.lastname: Patel
authors.forename: Rick B
authors.initials: RB
authors.lastname: Delamarter
mesh_terms: D000328:Adult; D000368:Aged; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage*; D016025:Bone Transplantation; D015331:Cohort Studies; D005260:Female; D005269:Femur / Q000637:transplantation*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016348:Osseointegration / Q000187:drug effects* / Q000502:physiology; D011446:Prospective Studies; D011542:Pseudarthrosis / Q000000981:diagnostic imaging / Q000209:etiology; D011859:Radiography; D011994:Recombinant Proteins / Q000008:administration & dosage*; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D016212:Transforming Growth Factor beta / Q000008:administration & dosage*; D014184:Transplantation, Homologous
chemical_list: D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2