Use of porous hydroxyapatite graft containing recombinant human bone morphogenetic protein-2 for cervical fusion in a caprine model.
OBJECTIVE
The efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2) for enhancing anterior cervical spine interbody fusion when added to a porous hydroxyapatite (HA) graft was investigated.


METHODS
Fourteen mature goats underwent three-level anterior discectomies after induction of endotracheal anesthesia. Porous HA grafts that contained 0, 5, and 50 microg of rhBMP-2 were placed concurrently with anterior cervical spine plates to achieve interbody fusion. The fusion rate, radiological findings, biomechanical stiffness, and histological appearance were evaluated in 42 spinal units immediately and again at 4 and 12 weeks after graft and plate placement. At 12 weeks postsurgery, manual testing showed a 100% fusion rate in the spines with HA grafts containing high-dose rhBMP-2; however, only a 50% fusion rate was shown in spines with grafts that contained no or low-dose rhBMP-2. On radiographic and histological studies the process of solid fusion was seen to be more advanced in relation to the use of larger amounts of rhBMP-2. Biomechanical testing demonstrated significantly higher stiffness values for grafts that contained high-dose rhBMP-2 than those without rhBMP-2 in flexion at 4 weeks, as well as in flexion, extension, and lateral bending tests at 12 weeks. Histological analysis demonstrated that rhBMP-2 increased the amount of bone apposition on the surface of the implants and promoted bone formation in the porous structure without increasing the penetration distance.


CONCLUSIONS
Through osteogenesis at the fusion site, the addition of rhBMP-2 to a porous HA ceramic graft enhances the rate of anterior cervical fusion.
Takahashi
T
T
Department of Neurosurgery, Tohoku University School of Medicine, Sendai, Japan.
Tominaga
T
T
Watabe
N
N
Yokobori
A T
AT
Sasada
H
H
Yoshimoto
T
T
D000818:Animals; D001696:Biomechanical Phenomena; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000627:therapeutic use*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D004305:Dose-Response Relationship, Drug; D017886:Durapatite / Q000627:therapeutic use*; D005260:Female; D006041:Goats; D006801:Humans; D011994:Recombinant Proteins; D013123:Spinal Fusion / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016212:Transforming Growth Factor beta
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; D017886:Durapatite