Fig. 1

Animal model. a. the caudal vertebrae were instrumented with K-wires only, which served as controls. b. the caudal vertebrae were immobilized using a custom-made external device to fix four caudal vertebrae (Co7-Co10). Four K-wires (50 mm in length and 1.2 mm in diameter) were fixed in parallel using two aluminum alloy cuboids (43 mm in length, 4 mm in width, net weight 5.0 g, the hole spacing is 12 mm), which do not compress or stretch the experimental discs