ABSTRACT
BACKGROUND: Upper cervical spine fractures are easy to lead to severe neurologic dysfunction in the elderly, and along with social progress, the incidence is on the rise. However, the diagnosis and treatment of type Ⅱ odontoid fractures in senile patients remain controversial.OBJECTIVE: To review the classification, treatment methods and clinical outcomes of type Ⅱ odontoid fractures in elderly patients.METHODS: A computer-based online search was performed in the PubMed and Wanfang databases for the articles concerning the diagnosis and treatment of type Ⅱ odontoid fractures in the elderly published from January 1996 to July 2016. The keywords were odontoid fracture, elderly, treatment, conservative, surgical in English and Chinese,respectively.RESULTS AND CONCLUSION: (1) The treatment goals of type Ⅱ odontoid fractures are different between elderly and young patients. (2) The incidence of nonunion in the conservative approach is higher than that in the surgical treatment, but for elderly patients, it makes no difference. (3) No significant differences are found in the incidence of complications and mortality between conservative and surgical methods in the elderly with type Ⅱ odontoid fractures. (4) Minimally invasive surgery is commended for the elderly suffering type Ⅱ fractures who cannot tolerate the conservative approach due to poor conditions or accompanied with other serious heart and lung diseases.
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.