The influence of different stress loading on the biomechanics of motion segments in isolated rabbit spines.

Intervertebral disc degeneration greatly affects daily life. Suitable mechanical stress is important for intervertebral disc health as it affects disc cells. Research shows it helps disc cell proliferation and collagen synthesis. However, the influences of forces in diverse directions on the intervertebral disc remain ambiguous. Our study aimed to investigate the impact of stress in various directions on intervertebral discs in New Zealand rabbits. The rabbit model was used because our team previously had established and validated it,which providing an effective platform for researching disc degeneration and treatment methods. We resected the spinal L3/4 and L5/6 motion segments and categorized them into 5 groups. Apart from the control group, distinct mechanical loads (pressure, traction, rotation, rotational traction) were applied to the remaining groups. After mechanical intervention, in contrast to the other groups except for the control group, it was found that the creep displacement in the rotational traction force group was the lowest (0.90 ± 0.06), the fatigue resistance was enhanced, and the tensile strength was increased, showing advantages over the other groups (p < 0.05). Histological examination revealed that the rotational traction force group had a protective effect on the intervertebral disc structure, while the cell damage in the rotational force group was the most severe. This study will help understand the unique effects of stresses in different directions on the intervertebral disc. The general public should avoid direct rotational movements in daily life. Physicians can explore the therapeutic effect of rotational movements under traction on lumbar degenerative changes.