Cervical interbody fusion cages. An animal model with and without bone morphogenetic protein.
METHODS
The Alpine goat model for multilevel anterior cervical discectomy and fusion was used to analyze the use of an intervertebral fusion device to promote an arthrodesis after anterior cervical discectomy. Comparisons were drawn with biomechanical, histologic, and radiographic data.


OBJECTIVE
To analyze the use of an intervertebral fusion device, with and without a bone graft substitute, to promote an arthrodesis anterior cervical discectomy.


BACKGROUND
In previous studies, the goat cervical spine has proven to be an excellent model for examining the healing of fusions using bone grafts, instrumentation, or bone substitutes.


METHODS
Three-level anterior cervical dissectomies were performed on 21 mature Alpine goats. Three treatment groups of seven goats each were used. Group I used a standard titanium cervical BAK device filled with autogenous bone graft. Group II used a hydroxyapatite-coated BAK device filled with autogenous bone graft. Group III used a BAK device filled with recombinant human bone morphogenetic protein-2.


RESULTS
Radiographically, no cages became displaced. Lucencies were seen around 3 of the 21 cages in Group 1, 4 cages in Group II, and none in Group III. Fluorochrome analysis revealed that the recombinant human bone morphogenetic protein-2-filled cages had an accelerated rate of bone growth around and through each cage-vertebral body interface at 3 weeks. A successful arthrodesis was also more likely with a recombinant human bone morphogenetic protein-2-filled cage (95%) than the hydroxyapatite-coated (62%) or the standard (48%) cage. Biomechanical stiffness testing did not reveal any statistically significant differences between the three groups. There was a tendency for successfully arthrodesed interspaces to be stiffer than those that were not.


CONCLUSIONS
The use of a threaded intervertebral fusion cage, with or without hydroxyapatite coating, filled with autogenous bone graft provides a fusion rate that is slightly better than those previously reported using autogenous interbody bone grafts with or without plate stabilization. Recombinant human bone morphogenetic protein-2-filled cages resulted in a much higher arthrodesis rate and accelerated bone formation compared with either autogenous bone-filled BAK devices, or autogenous interbody bone grafts with or without plate stabilization.
Zdeblick
T A
TA
Division of Orthopedic Surgery, University of Wisconsin, Madison, USA.
Ghanayem
A J
AJ
Rapoff
A J
AJ
Swain
C
C
Bassett
T
T
Cooke
M E
ME
Markel
M
M
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D001861:Bone Regeneration / Q000187:drug effects; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000502:physiology / Q000601:surgery*; D019245:Compressive Strength; D017586:Diskectomy; D005260:Female; D005456:Fluorescent Dyes; D006041:Goats; D007596:Joints / Q000502:physiology; D008422:Materials Testing; D019736:Prostheses and Implants; D011859:Radiography; D011994:Recombinant Proteins / Q000494:pharmacology; D013123:Spinal Fusion / Q000379:methods*; D014025:Titanium; D014102:Torsion Abnormality; D016212:Transforming Growth Factor beta / Q000032:analysis
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D005456:Fluorescent Dyes; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D014025:Titanium