Biomechanical investigation of hybrid fusion and non-fusion cervical spine surgeries-A finite element analysis

• Main Authors: Ming-Hsun Tsai, 蔡明勳
• Other Authors: Weng-Pin Chen, Chang-Jung Chiang
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/db4zcb

碩士 === 國立臺北科技大學 === 製造科技研究所 === 103 === Cervical Spine Intervertebral discs diseases have received more and more attention in recent years. There are two types of surgery applied in this disease, fusion surgery and non-fusion surgery. Although, Fusion surgery can resume the height of discs and relieve pain from patient. However, this method will limit the motion of the implanted levels and cause a compensation of motion in adjacent levels. This result will speed up the discs function degeneration. In recent years, there have been many studies on artificial disc cervical replacement surgery, because it has an active joint surface which will have interactive activities with artificial disc, but there exists a wearing problem in the joint surface. The effect of combing fusion surgery and non-fusion surgery in cervical spine has not been widely discussed recently. In our research, we proposed a biomechanical comparison of the three surgergical methods on the cervical spine based on finite elements analysis. This research created an intact C2-T1 spine with interbody fusion cage and/or artificial disc models. The implants are implanted into the discs between C4-C5 and C5-C6 to simulate non-fusion, fusion and hybrid surgeries under four types of loading, flexion, extension, lateral bending, and axial rotation. By using finite element analysis, we are able to investigate the range-of-motion (ROM) patterns of each motion segments, as well as the compression stress in the nucleus, the maximum value and distribution of the implant stress, and the stress in the facet joint. The results showed that when bi-level interbody fusion cages were implanted into the discs under the four types of loading, the ROM’s of the operated levels are almost the lowest. Moreover, the compensation effects in the adjacent levels become more significant. Due to the compensation phenomenon, it leads to the increase of the adjacent inner pressure in the nucleus and high stress in the facet joint. As compared to the implant stress of other implant models , the stress in the implant is the highest. When a single disc fusion cage and an artificial disc were implanted, lower compensation of motion was found. As for the inner pressure in the nucleus and the facet joint stress stay close to the intact model. Because the cervical artificial disc is designed with movable joint surfaces, it is able to reduce the maximum stress in the implant. We could conclude that when bi-level artificial discs were implanted under the loadings of flexion, lateral bending, and axial rotation, the range of motions in the operated levels are closer to that of intact model. Otherwise, under the extension loading, the range of motion is much higher, it might cause the loading in the facet joint to increase and the stress in the adjacent nucleus and facet join to be reduced. This results showed the alleviation of degeneration in the adjacent discs According to the simulation results, bi-level non-fusion surgery possesses better biomechanical performance on the intervention treatment of cervical spine degeneration disease. However, there are still concerns such as the increase of the facet joint load at the operated level that might speed up the facet joint degeneration. Therefore, the hybrid surgery with cage and artificial disc has the benefit of closer stress values in the adjacent level nucleus and facet joint load. It might be a better choice than bi-level fusion surgery.