Fixed The Mechanical Characteristics And Comparative Study Of Three Kinds Of Internal Fixation Of Thoracolumbar Spine Fractures

Objective Since 1.980's, with the invention of transpedicle screw, the curative effect of operation to pedicle of vertebral arch has shown out a significant superiority to the traditional conservative treatment. With the further research on qualitative and quantitative anatomy and spinal column biomechanics, the biochemical theory on anatomical restoration by three-dimensional space of spinal column fracture and the mechanism of anatomical reduction have been proved by experiments, which provides the basis for the design of various internal fixation devices. With such basis, we designed a system called ARRIF, and by mechanical contrast study with the Dick and AF prevailing in clinic now at home and abroad, the reliable basis for further clinical application has been gained. Method A single spinal compression fracture model and a model of spinal compression fracture with three-axes spinal damages were made according to the Panjabi Method with the thoraculumnbar spinal column specimens taken from six fresh cavaders. According to the Latin Square experimental designing principle, the fracture specimens were fixed witi~i ARRIF, Dick and AF separately and axial compression, forward flexion, lateral bending and axial torsion load were given. The shift and angle changes were observed under different loads, and the analysis of variance was performed to all the data with the SPSS software. If differences appear, pair contrast study was performed to the mean of the data to decide the similarities and differences of the mechanical features. At the same time, the changes of the bone trabecula round the vertebral nail pass were observed to set the accuracy of the experiment results. Results The single spinal compression fracture model showed no significant shift and the mechanical features are similar when it was fixed by ARRIf, AF separately and axial compression, forward flexion and lateral bending loads were given. The model of spinal compression fracture with three spinal damages showed similar mechanical feature in the three fixings when vertical tension was given. However, significant differences were shown out in the three fixings when axial torsion load was given. The pair contrast study was performed with the means of angle changes. When the angel change under 10 ~, ARRIF showed out significant superiority to Dick and AF. But when the angel changed within 10 to 20 ~, ARRIF and AF showed out clearly a superiority to Dick, the histological observation of ARRIF recorded no significant changes of the bone trabecula round the nail pass and the structure kept normal. Conclusion The mechanical feature of ARRIF was basically similar to that of AF and Dick. Because of the characteristics of its designing, its ability of anti-axial torsion is significantly superior to that the other two. It can be easily fixed in application, and it can save the operation time, reduce bleeding and the possibility of infection, thus it holds certain value in clinical practice.