Abstract: ponding Abstract： Objective To establish an animal model of annulus fibrosus (AF) partial defect for the repairing of interver⁃ tebral disc (IVD) defect. Methods Image J 1.46r software was used to measure the T12/L1-L6/S1 intervertebral height in ovine lumbar spine X-ray films. AF thickness was measured by axial split disc. A 11 blade was used to make a trapezoid de⁃ fect of upper bottom 3 mm, lower bottom 5 mm, height 5 mm and thickness 3 mm, whose lower bottom toward the nucleus pulposus (NP) in the left front of ovine lumbar IVD in vitro. The minimally invasive lateral approach was used to make the same type of trapezoid defect in the left front of the ovine lumbar IVD in vivo. The trapezoidal defect length of the axial divid⁃ ing disc was measured, AF and a small amount of NP from trapezoidal defect in IVD were weighed, and the production of trapezoidal defect in IVD was evaluated. Results The lumbar intervertebral space height of ovine was (4.45±0.28) mm. There were significant differences in the thickness of AF (4.08±0.50) mm , thickness (3 mm) and height (5 mm) of trapezoidal defect (P < 0.05), respectively. There were no significant differences in trapezoidal defects in ovine lumbar IVD in vitro on the upper bottom (3.03±0.09)mm, the lower bottom (5.03±0.09) mm, the height (4.97±0.10) mm, the thickness(3.02±0.06) mm and the trapezoidal defect predetermined value on the upper bottom 3 mm, the lower bottom 5 mm, the height 5 mm and the thickness 3 mm (P > 0. 05). The weights of the AF and NP taken out from ovine lumbar IVD in vitro and in vivo were (0.162 ± 0.011) g and (0.166 ± 0.014) g, and there was no significant difference between them (P > 0.05). Conclusion Through the operation of minimally invasive lateral approach, the method of making a trapezoidal defect in the experiments can establish animal model of AF partial defect, which meets the requirements for the repairing of IVD defect, and is simple, safe and reliable

Key words: models, animal, diskectomy, tissue engineering, sheep, annulus fibrosus defect, intervertebral disc defect