Stress analysis of a plate-rod system for scoliosis correction

To study the stress-strain relationships of intervertebral discs and vertebrae when using a plate-rod system for scoliosis, a mechanical model of scoliosis was built based on the similarity principle. The stress variation on the spine, which was under the coactions of lengthwise load and correcting load, was measured by photoelastic and strain gauge methods. The model test results indicate that the added value of compressive stress on the concave side of the spine (0-1.5 MPa) is larger than the added values of compressive stresses on the spine's convex side and concave ligament (0-200 N). This demonstrates that the lengthwise load (weight) can increase the seriousness of scoliosis. In addition, it was shown that tensile stress is formed on the concave side of the scoliosis model when the compressive stress decreases (1.5-0 MPa), due to the effect of the correcting load. It can be seen that plate-rod systems can correct scoliosis effectively.