INTERVERTEBRAL DISC AUTOGRAFTING IN A BIPEDAL ANIMAL-MODEL

Fusion of the spine while restoring stability of the spinal segment, f ails to preserve spinal mobility. Long term complications of accelerat ed degeneration in the neighboring segments have been reported. The pr esent study explores the possibility of intervertebral disc autografti ng in a bipedal animal model by isolating a lumbar disc together with the adjacent end plates and repositioning it with minimal internal fix ation. Fourteen Rhesus monkeys were sacrificed at 2, 4, 6, and 12 mont hs after surgery and the grafted discs were examined radiologically, b iochemically, pathologically, and biomechanically, Healing of the bony end plate was seen between 2 to 4 months postoperatively, There was e arly loss of disc height at 2 and 4 months but there was a suggestion of some reconstitution up to 12 months. There was minimal evidence of gross degeneration at all stages, Gradual loss of water content was fo und in the annulus and the nucleus, The nucleus pulposus seemed to be able to reaccumulate proteoglycan after an initial drop in the first 4 months, There was significant increase in hydroxyproline content in t he annulus fibrosus and the nucleus pulposus. Biomechanically, the gra fted disc showed hypermobility in the first 4 months but gradually bec ame stabilized with time. Results from this study suggested that a fre sh intervertebral disc autograft could survive a period of ischemia. A lthough the physiology of the disc was deranged, it was able to preser ve a certain degree of segmental mobility without sacrificing stabilit y. Further studies are required to validate these results and the fiel d of disc allografting should be explored.