Sheep lumbar intervertebral discs as models for human discs

Objective. To determine the water content, collagen content and collagen orientation angle in different regions of sheep lumbar discs. Design. A laboratory study of sheep discs obtained from an abattoir. Methods. A total of 21 sheep lumbar discs were obtained from three lumbar spines. Water content was determined by oven drying (60 °C) to constant mass. Collagen content was determined by hydroxyproline analysis. Fibre orientation angles were determined by X-ray diffraction. Results. Water content increased from 74% of total tissue mass in the outer annulus, to 82% in the inner annulus, to 86% in the nucleus. Collagen content decreased from 30% of total tissue mass in the outer region to 20% in the inner region of the anterior and lateral annulus; it was 16% in the posterior annulus. The orientation angle of the collagen fibres decreased from 59° in the outer region to 56° in the inner region of the anterior and lateral annulus; it was 51° in the posterior annulus. Conclusions. Sheep lumbar intervertebral discs provide a reasonable model for human lumbar intervertebral discs.