Strut allograft union and remodeling using rhBMP-2 in a spinal corpectomy model.
METHODS
Growth factor in a collagen sponge carrier was compared to autograft, both packed within an allograft strut following corpectomy in a bovine spinal model.


OBJECTIVE
To evaluate incorporation of cortical strut allografts after lumbar corpectomy, comparing augmentation with recombinant human bone morphogenetic protein-2 (rhBMP-2) to local autograft.


BACKGROUND
Autogenous strut grafts are the gold standard for successful fusion in reconstruction following corpectomy; however, significant donor site morbidity can occur. Recent studies describing consistently successful anterior interbody fusions with BMP augmentation suggest an exciting prospect of unlimited and potent grafting material for these difficult fusions.


METHODS
Sixteen calves underwent L3 corpectomy with instrumented strut allograft reconstruction. The rhBMP-2 impregnated collagen sponges filled the empty medullary canal of the allograft in 8 animals. Eight animals had the allograft strut filled with local autogenous bone. After 4 months, the lumbar spines were harvested for radiographic, biomechanical, and histologic evaluation.


RESULTS
Computerized tomography revealed allograft fusion in 7 of 8 autograft specimens and 8 of 8 BMP specimens. The BMP treated group had denser bone at the ends of the cortical allograft, but a central void persisted. Autograft filled struts maintained a more uniform distribution of less organized bone throughout the strut canal. Histologic assessment verified remodeling and incorporation of the allografts for both groups. Biomechanical testing confirmed no significant difference in fusion strength between groups.


CONCLUSIONS
Large cortical strut allografts (after lumbar corpectomy) supplemented with rhBMP-2 had incorporation and fusion strength comparable to allografts enhanced with cancellous autograft.
White
Klane K
KK
Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA.
Bawa
Maneesh
M
Ahn
Jae-Sung
JS
Farnsworth
Christine L
CL
Faro
Frances D
FD
Mahar
Andrew T
AT
Wedemeyer
Michelle
M
Garfin
Steven R
SR
Newton
Peter O
PO
D000818:Animals; D019643:Arthroplasty, Replacement / Q000295:instrumentation / Q000379:methods*; D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D016025:Bone Transplantation; D002417:Cattle; D003094:Collagen; D004337:Drug Carriers; D006801:Humans; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000473:pathology / Q000601:surgery*; D008297:Male; D023421:Models, Animal; D016348:Osseointegration / Q000187:drug effects* / Q000502:physiology; D011994:Recombinant Proteins / Q000494:pharmacology*; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D001672:Biocompatible Materials; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D004337:Drug Carriers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D003094:Collagen