Does plate fixation prevent disc degeneration after a lateral anulus tear?

Abstract

The sheep model was used to investigate the development of disc degeneration after outer anular tearing. The authors determined whether plate fixation promotes healing of peripheral anular tears and thereby minimizes disc degeneration. A limited outer anular tear (similar to the rim lesion) in the sheep lumbar disc causes progressive and irreversible degeneration within 6 months. Incomplete healing of the tear may result from continued movement in the vicinity of the lesion. In 15 sheep, a cut 4 x 10 mm was made in the lateral anulus of two nonadjacent lumbar discs, and a metal plate was fixed across one. Three sheep were killed immediately, and the remainder were killed after 6 months for histologic examination. There were no significant differences in propagation of the cut through the inner anulus, extent of healing, or extent of nuclear degeneration, between plated and nonplated motion segments after 6 months. Vascularization of the cartilage endplate was significantly increased on the operated side (P < 0.01), but remained unchanged on the nonoperated side. Disc degeneration was not prevented by this method of plate fixation, despite similar but limited healing of the outer anulus tear in both plated and nonplated levels.