| There is a great potential risk in the atlantoaxial instability accurs in clinic which needs timely surgical intervention. At present,the posteromedian road internal fixation is still the mainstream method for the treatment of the atlantoaxial instability. However, for some cases, such as atlantoaxial posterior bony structure was lost due to the congenital and iatrogenic, atlantoaxial dislocation happens in neck flexion and reset in neck extension, posterior atlantoaxial fixtion is not possible. At the same time,the biomechanics of anterior transarticular screw fixation in flexion and extension is not enough to achieve satisfactory. In this case,our department independently developed the anterior atlantoaxial transarticular locking plate system,providing a new way to solve the difficulties encountered in the posterior surgery and the shortcomings of the anterior transarticular screw fixation.This operation is very difficult and challenging because of the atlantoaxial complex anatomy structure and adjacent relations, so how to establish a simple and reliable preoperative design method to guide the fixation system’improvements and the operation smoothly is very important.A lot of measurements in dry atlantoaxial showed that atlantoaxial is suitible to anterior and posterior fixation,having been made by many scholars at home and abroad.However, it has not been reported that how to make the anatomical measurement and the preoperative plan on the reconstruction films of multi-slice spiral computer tomography (MSCT) before anterior atlantoaxial transarticular locking plate fixation.Therefore, this study will focus on how to use the multi-slice spiral computer tomography three-dimensional reconstruction technique for preoperative plan of anterior atlantoaxial transarticular locking plate fixation,and to verify the reliability of the planning method through the measurement on the cadavers and adult volunteers. Objective:To explore a simple and reliabl preoperative plan of anterior atlantoaxial transarticular locking plate fixation through measurement on multi-slice spiral computer tomography films and the verification of the operation simulation on cadavers.Method:l.The20sets of normal Chinese adults atlantoaxial specimens soaked in formalin and30healthy Chinese adult volunteers were scanned and reconstructed by multi-slice spiral computer tomography (MSCT) at line2.0mm thick,1.0mm thick. Then we used spiral computer tomography three-dimensional reconstruction technique of volume reconstruction (VR) and multiplanar reconstruction (MPR) techniques to establish the measurement program;2.Acorrding to the requirements of the anterior atlantoaxial transarticular locking plate fixation, AW three-dimensional measurement software was used to measure screw placement’s individual anatomical data on GE RA600PACS workstation. The data was analysed statistically to evaluate the safety of the screw trajectory;3. To verify the feasibility of multi-slice spiral computer tomography three-dimensional reconstruction images as a method of the preoperative planning, six anticorrosive atlantoaxial specimens were used to simulate the operation according to the data measured by AW three-dimensional measurement software on GE RA600PACS workstation.Results:1.The multi-slice spiral computer tomography three-dimensional reconstruction technique in volume reconstruction (VR) and multiplanar reconstruction (MPR) technology could satisfy the the preoperative planning needs of the anterior atlantoaxial transarticular locking plate fixation,MPR axial, sagittal,coronal reconstruction could meet the individualized requirements of screw insertion point and screw insertion angle;2. The insertion point of anterior atlantoaxial transarticular locking plate fixation was at the junction of the lateral edge of the axis vertebral body to4mm above the inferior edge of the axis anterior arch.In the anterior transarticular screw fixation, the lateral angulation of the screw tract to the sagittal plane ranged from17.69°to21.13°, the posterior anguation to the coronal plane from11.75°to19.50°, the medial screw tract length was from11.19mm to27.51mm, the lateral screw tract length was from15.61mm to31.84mm;3.After inserting surgery, the screw trajectores in all postoperative specimen were located in safe area, no one was worn out on the atlas articular surface;4.The angle of preoperative plan and the actual angle of the postoperative were measured and recorded respectively.Then the meaasured datas were matched t test through the SPSS13.0software.(P>0.05,the results show that the actual angle and planning angle have no significant difference);5.In the edge of atlas hole horizontal, atlantoaxial joint surface and lower edge of the atlantoaxial joint surface three MPR cross section, There was certain distance between the screw and spinal cord, vertebral artery. The nearest distance between the screw and the spinal was6.51±0.32(mm)at the cross-section B, while the nearest distance was5.52±1.22(mm) between the screw and vertebral artery at the cross-section C. The distance from the screw to the joint surface of atlas lateral mass is2.80±0.12(mm).No screw injury happened on spinal cord, vertebral artery and atlanto-occipital articulation.Conclusion:1.The anterior atlantoaxial transarticular locking plate fixation is safe and feasible.It is optimal for the anterior atlantoaxial transarticular locking plate fixation to place the anterior atlantoaxial transarticular screw with the length of16mm to28mm in lateral angulation ranged from18°to21°and the posterior angulation ranged from12°to20°measured by multi-slice spiral computer tomography three-dimensional reconstruction technique;2.The anterior atlantoaxial transarticular locking plate fixation guided by the existing multi-slice spiral computer tomography three-dimensional reconstruction technique can get the preoperative anatomical structure details,reasonable preoperative design and individualized measurement data.According to the measurement result to guide the operation,operation is not just rely on feeling and experience. There are more possibility for success of screw placement,in which operation time can be decreased and efficiency can be improved;3.Due to the multi-slice spiral computer tomography three-dimensional reconstruction post-processing technique is mainly used for disease diagnosis, there is interactivity,less specific limitations, lack of quantitative standard if the technique used for the operation plan, so intraoperative monitoring of the radiology is needed to correct procedural errors. |
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