Finite-element analysis of a novel posterior atlantoaxial restricted non-fusion fixation system / 中国组织工程研究

ABSTRACT

BACKGROUND:Atlantoaxial fusion is currently the main surgical treatment of atlantoaxial dislocation, but the premise is at the expense of atlantoaxial range of motion, especial y the rotation motion. Restricted non-fusion fixation is a method that can maintain the atlantoaxial stability, while retain the atlantoaxial range of motion. Further research should be performed to compare the biomechanical characteristics between the two methods. OBJECTIVE:To develop a three-dimensional finite element model of atlantoaxial instability, compare and determine the biomechanical properties of posterior atlantoaxial restricted non-fusion fixation system and posterior atlantoaxial screw-rod fixation system. METHODS:A verified intact finite element upper cervical (C0-C3) model was established and analyzed by Simpleware 3.0, Geomagic 8.0, Hypermesh 10.0, Abaqus 6.9, and Rhino 4.0 softwares based on the CT data col ected from a 31-year-old healthy male volunteer. The moment couple of 1.5 N?m was loaded, which made the model movement in flexion-extension, lateral bending, and rotating direction, respectively. The range of motion was recorded and compared with the in vitro biomechanical experimental data to verify the effectiveness of the model. The ranges of motion of the posterior atlantoaxial restricted non-fusion fixation system model and the posterior atlantoaxial screw-rod fixation system model were analyzed using the finite element method under flexion, extension, lateral bending, and axial rotation;meanwhile, stress nephograms of the posterior atlantoaxial restricted non-fusion fixation system model were observed. RESULTS AND CONCLUSION:(1) There were 206 747 elements and 72 500 nodes in the intact model of upper cervical spine (C0-C3) in this experiment, and the range of motion of intact model validated with the reported cadaveric experimental data. (2) The range of motion of the posterior atlantoaxial restricted non-fusion fixation system group was similar to which of the posterior atlantoaxial screw-rod fixation system group in flexion-extension direction. (3) In lateral bending direction, the range of motion of the posterior atlantoaxial restricted non-fusion fixation system model was obviously limited, respectively. The range of motion of the posterior atlantoaxial restricted non-fusion fixation system model was larger than that of the atlantoaxial dislocation model and basical y same as that of the normal atlantoaxial model. (4) As to the rotating direction, the range of motion of the posterior atlantoaxial restricted non-fusion fixation system mainly disappeared at the atlantoaxial segment;by contrast, a majority of rotating motion was stil retained in the posterior atlantoaxial restricted non-fusion fixation system group. (5) The stress concentration occurred in the contact part between the screw and the connecting rod in posterior atlantoaxial restricted non-fusion fixation system model. (6) Results suggest that posterior atlantoaxial restricted non-fusion fixation system is effective and useful for atlantoaxial fixation. It not only restricted atlantoaxial flexion-extension, but also preserved axial rotation and lateral bending at the atlantoaxial joint.