Development of an artificial vertebral body using a novel biomaterial, hydroxyapatite/collagen composite

Hydroxyapatite/collagen (HAp/Col) composites having a bone-like nanostructure were synthesized and shaped into implants. This study was designed to develop an artificial vertebra system using this novel implant for anterior fusion of the cervical spine. Anterior fusion was carried out on 6 beagle dogs with the implants adsorbing rhBMP-2 (400 μg/ml), and 9 dogs with the implants without rhBMP-2. In 3 dogs of the rhBMP-treated group, as well as 6 dogs of the non-rhBMP-treated group, the implant was fixed with a poly- -lactide plate and 2 titanium screws. Implants were taken out after 13 weeks from each 3 dogs in the rhBMP(−):plate(−), rhBMP(−):plate(+) and rhBMP(+):plate(+) groups. Also, the implants were removed from each 3 dogs in the rhBMP(−):plate(+) and rhBMP(+):plate(+) groups after 24 weeks. Histological and radiographical analysis suggested that since the larger part of the composite material was absorbed within 13 weeks, reduction of the intervertebral distance was caused, and that enhancement of callus formation and bone bridging by rhBMP-treatment was effective to prevent collapse of the implant, even though an effect of anterior plate-fixation was not obvious. The HAp/Col implant adsorbing rhBMP-2 may be a suitable replacement for the existing ceramics in anterior interbody fusion of the cervical spine.