Three-dimensional finite element analysis of the biomechanical changes of the lumbar spine after the combination of intervertebral fusion with dynamic internal fixation of the interspinous process in the lumbosacral region
10.3969/j.issn.2095-4344.2543
- Author:
Liangliang CAO
1
Author Information
1. Zhengzhou Orthopedics Hospital
- Publication Type:Journal Article
- Keywords:
Adjacent segment degeneration;
Biomechanics;
Finite element analysis;
Lumbar spinal fusion;
Range of motion;
Topping-off
- From:
Chinese Journal of Tissue Engineering Research
2020;24(12):1905-1919
- CountryChina
- Language:Chinese
-
Abstract:
BACKGROUND: The Topping-off technique, which combines lumbar fusion with the dynamic internal fixation system (Coflex), can not only reduce the pressure, but also protect the adjacent segments. There is no relevant mechanical analysis performed on the rationality of the application of Topping-off technique to young patients with the need for fusion on the lumbosacral region and adjacent degenerated segments. OBJECTIVE: To establish a finite element model of Topping-off surgery on the lumbosacral junction and to analyze the biomechanical changes of the adjacent segments and the range of motion trend of the lumbar spine. METHODS: A healthy young male volunteer with no previous history of low back pain or congenital malformations was randomly selected for thin-slice CT scanning after signed the informed consent. The image information was imported into the computer and the whole lumbar spine model as the healthy group model was established by analyzing the image information through Mimics, Geomagic Studio 12.0, HyperMesh and Abaqus successively. After verifying the effectiveness of the model, the moderate degeneration model of intervertebral disc was established by changing the material properties of L4-s1 discs on the basis of the healthy model, and the fusion model and Topping-off model were respectively established on the basis of the degeneration model. After applying 400 N compressive load and 10 N-m momentum to the four groups of models, the variation trends of range of motion from L2 to L5 and the stress changes of L4/L5 intervertebral disc, nucleus pulposus and facet joints were calculated respectively. RESULTS AND CONCLUSION: (1) Compared with the degeneration model, the lumbar range of motion of Topping-off model and fusion model decreased, and the Topping-off model decreased more significantly than the fusion model. (2) The range of motion of fusion model L4-L5 increased significantly and the range of motion of L2/L3 and L3/L4 segments did not change significantly. Compared with the degeneration model, the L4-L5 range of motion of Topping-off model decreased, and range of motion of the L2/L3 and L3/L4 levels increased to some extent in the flexion and extension positions. (3) Compared with the degeneration model, the stress on the disc, nucleus pulposus and facet joint of the fusion model L4-L5 increased in four positions of flexion, extension, rotation and bending, while the fiber stress on the Topping-off model decreased significantly in all four positions. (4) These results suggest that Topping-off technology can not only reduce the stress on the upper adjacent degenerative intervertebral disc, nucleus pulposus and facet joints, but also reduce the hyperactivity of the adjacent segments and increase the range of motion of other upper segments, thereby compensating the lumbar spine mobility and delaying the degeneration of upper adjacent segments.
