The Optimal Analyses and Biomechanical Experiments of Cervical Vertebral Body Cage: Subsidence and Loosening

• Main Authors: Long-Ming Lu, 陸隆鳴
• Other Authors: Ching-Kong Chao
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/18844262341842019663

博士 === 國立臺灣科技大學 === 機械工程系 === 101 === In clinical trials, the vertebral body cage with anterior cervical discectomy and fusion has been widely used to treat cervical diseases and to recover cervical function. In clinical follow-up, failure of the vertebral body cage regularly occurred and resulted in failure of bone fusion and in implant breakage. The subsidence and loosening were the most commonly occurring clinical failures. Therefore, a three-dimensional finite element model of cervical spine with vertebral body cage and biomechanical test were developed to evaluate the intensity of subsidence and retropulsion resistance for different situations of insertion depth. Moreover, the issues of bone fusion, bone mineral density, endplate preservation and implant material are discussed in detail. In the optimal parametric analyses of subsidence and retropulsion, a three-dimensional finite element model of the cervical spine and vertebral body cage were reconstructed after refering to images of author’s multi-slice computed tomography scan. In order to obtain the optimal parameter design of the vertebral body cage and contribution of factor, the Taguchi method was employed to analyze signal to noise ratio and variance. In the meantime, a compressive test and pullout test were also excuted. From the results of parametric analyses of different insertion situations, the ring type, the number of spike and inner diameter were the important factors for the subsidence and the height of spike and ring type were the important factors for the loosening. Afterwards, the design parameter of the spike played a more important role in the situation of non-completed sinking. The main determination is the amount of the interfacial contact area perpendicular to the direction of subsidence and retropulsion, in that the greater the contact area, the more significant improvement of failure resistance. There was a high correlation between finite element analyses and biomechanical experiments, which were over 0.95 and 0.90 for subsidence and loosening, respectively. The analyses of another four variables: the bone fusion, bone mineral density, endplate preservation and implant material, were also performed to estimate subsidence and retropulsion resistance. The results showed that the factor of bone fusion was not significant. As such, the resistance ability was increased when bone mineral density and endplate preservation were increased. Finally, the material of polyetheretherketone was an option when reducing the failure and stress shielding. In this dissertation, the research results offer reference information for clinical orthopedic surgeons and engineering-related researchers.