Effect of nano-hydroxyapatite/collagen composite and bone morphogenetic protein-2 on lumbar intertransverse fusion in rabbits.
OBJECTIVE
To investigate the effect of nano-hydroxyapatite/collagen (nHA/collagen) composite as a graft extender and enhancer when combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) on lumbar intertransverse fusion in rabbits.


METHODS
Sixty-four adult female New Zealand white rabbits, aged 1 year and weighing 3.5-4.5 kg, underwent similar posterolateral intertransverse process arthrodesis and were randomly divided into 4 groups based on different grafts: autogenous cancellous bone alone (ACB group), nHA/collagen alone (HAC group), half autogenous cancellous bone and half nHA/collagen (ACB+HAC group) and nHA/collagen combined with rhBMP-2 (HAC+BMP group). The fusion masses were analyzed by manual palpation, radiography, biomechanical testing and histological examination.


RESULTS
Fusion was observed in 4 cases in the 6th week and in 5 cases in the 10th week after surgery in ACB group. No case showed fusion in HAC group. In ACB+HAC group, there was fusion in 3 cases in the 6th week and in 4 cases in the 10th week after surgery. In HAC+BMP group, fusion in 1 case was found in the 4th week, in 5 cases in the 6th week and in 6 cases in the 10th week after surgery. It suggested that ACB, ACB+HAC and HAC+BMP groups showed similar fusion ratio and mechanical strength in the 6th and 10th week after surgery. According to the microstructure analysis of the samples, nHA/collagen had no negative effect when implanted together with ilium autograft. In HAC+BMP group, new bone-like tissue was observed in the 2nd week postoperatively, and nearly all of the implanted composites were replaced by mature bone matrix and new bones in 10th week postoperatively.


CONCLUSIONS
The nHA/collagen, especially combined with rhBMP-2, is a promising bone substitute, for it has quick biodegradation, fine bone-bending ability, and high osteoconductivity on posterolateral spinal fusion in rabbits.
Sun
Tian-sheng
TS
Department of Orthopaedics, General Hospital of Beijing Military Command, Beijing 100700, China. sunts@163bj.com
Guan
Kai
K
Shi
Shu-shan
SS
Zhu
Bing
B
Zheng
Yong-jun
YJ
Cui
Fu-zhai
FZ
Zhang
Wei
W
Liao
Su-san
SS
D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D004195:Disease Models, Animal; D017886:Durapatite / Q000494:pharmacology*; D005260:Female; D008159:Lumbar Vertebrae / Q000187:drug effects* / Q000601:surgery; D016348:Osseointegration / Q000187:drug effects*; D011336:Probability; D011817:Rabbits; D012680:Sensitivity and Specificity; D013123:Spinal Fusion / Q000379:methods*; D013718:Tensile Strength; D016212:Transforming Growth Factor beta
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta; D017886:Durapatite