| dc.description.abstract | In recent years, there has been a growing development of non-fusion lumbar spine surgeries. The main objective of these surgeries is to provide lumbar stability without compromising mobility, and they are reversible unlike fusion surgeries. In clinical practice, various types of implants are used to treat different lumbar pathologies and evaluate their effectiveness. Commonly evaluation methods include clinical trials, cadaveric experiments, and simulation analyses. The finite element method is widely used to assess the biomechanical effects of implants on the lumbar spine because it is difficult to determine the stresses of post-implants clinically.
Although there are various posterior lumbar spine systems available on the market, these implants still have some limitations. They may not achieve the desired function due to limitations imposed by material properties or patient-specific factors such as bone density. This study focuses on the design of pedicle-based stabilizers, including a new design, which aims to avoid excessive rigidity caused by material properties, compensation, or limitations on activities such as flexion and extension. The goal is to maximize clinical benefits and prevent adjacent segment degeneration.
The intervertebral distance induced by the implant has an impact on the initial stability of lumbar spine biomechanics. However, there is no literature that evaluates the initial stability resulting from implant support and proposes a reasonable method for setting the intervertebral distance. Therefore, this study compares the effects of intervertebral distance by simulating the intervertebral distance after implant installation using ligament preloading.
This study establishes a lumbar spine model of the L3-L5 segment for finite element analysis, including both healthy and degenerated conditions, to analyze the biomechanical performance of the human lumbar spine and the implants.
The results show that degenerated lumbar spines experience reduced segmental mobility and gradually transfer stresses to the annulus fibrosus due to dehydration and changes in intervertebral disc geometry. The mobility of adjacent segment increases due to compensatory phenomena, thus increasing the stresses on the intervertebral disc. Without ligament preloading, both pedicle-based stabilizer models restrict flexion and extension of the lumbar spine, leading to increased compensatory mobility in adjacent segments. The intervertebral disc-related indicators are similar to those of a healthy spine, with no significant decompression effect to indicate implant support. With ligament preloading, both stabilizer models can limit flexion and extension, and the addition of PEEK material in the new pedicle-based stabilizer results in more restriction on mobility. The intervertebral disc-related indicators demonstrate better support with the new stabilizer. Overall, the new pedicle-based stabilizer reduced the range of motion of the implanted segment by about 10%, but it had better support and less impact on adjacent segments. Intervertebral stability may be underestimated if ligament prestress is not considered in finite element analysis. Limitations of this study include the use of isotropic material properties, the location and magnitude of ligament preloading, and the absence of muscle forces, which need further investigation. | en_US |