Vertebral column allografts for the treatment of segmental spine defects. An experimental investigation in dogs.

Vertebral column allografts, with their intervertebral discs, were implanted into thoracic spine defects (T7-T9) in 11 dogs in an attempt to re-establish spinal stability and preserve spinal biomechanics. Before implantation, the allografts were harvested under sterile conditions from similar-sized dogs and deep frozen at -80 C. The animals were followed for 18 months postoperatively. Radiographs demonstrated gradual loss of intervertebral disc height. Biomechanical analysis showed that the dogs with allografts had no significant difference in spine stiffness compared with normal spines in compression, flexion, and extension testing. Control spines that had been fused were significantly stiffer than the allograft spines in all modes tested (P less than 0.05). Histologic analysis showed incorporation of the allograft but with incomplete revascularization of the allograft's eighth thoracic body. This investigation found that vertebral body allografts with intervertebral discs can function successfully for 18 months in a canine model. This research may assist in the development of physiologic treatment for spinal deficiencies in humans.