[Experimental study of chemical spinal fusion in the rabbit by means of bone morphogenetic protein]

Bone morphogenetic protein (BMP) is known to induce mesenchymal cell production of cartilage. During the regeneration process after chemonucleolysis, fibroblastic cells are supposed to migrate into the disc space. These migrated cells could contain BMP-responding cells. The present study was undertaken to investigate anterior spinal fusion of rabbits produced by intradisc injection of BMP after chemonucleolysis with chymopapain. After intradisc injection of BMP, roentgenographs revealed calcification of disc space. Calcification was more obvious in discs pretreated with chymopapain than in non-pretreated discs. Histology showed this calcification to be ossification of the nucleus pulposus and the anterior longitudinal ligament. Ossification was more obvious along the anterior longitudinal ligament than in the nucleus pulposus. In some cases, ossification led to the formation of bony bridges along the anterior longitudinal ligament. These results indicate that anterior spinal fusion can be produced by intradisc injection of chemicals.