Biomechanics Study On The Stress The Parallel Nailing And Cross Nailing Methods Of Anterior Cervical Plate Screw Internal Fixation System

Objective:To compare the stress on the screw tail between parallel and cross methods of anterior cervical plate screw internal fixation system, so as to provide a theoretical basis for screw placement in surgery.Materials and methods : Eighty-eight fresh goat cervical vertebras(contain C4-C6) were prepared, and randomly divided into four groups, twenty-two for each group. Four screws of each were cross-linked by connecting rods and connector,group A and C for parallel implantation, group B and D for cross implantation, and then making a Pulling out test on the universal testing machine according to the axis direction of the screw for group AB. Fatigue test was conducted for group CD. SPSS16.0 was taken for statistical analysis.Results:The values of the maximum axial pullout strength of group A were1101.7±238.213 N, group B were 1190.7±247.652 N. No statistical difference were observed(P>0.05); Both group C and D shown approximately 0.055×107fatigue strength in fatigue test, there was also no statistical significance.Conclusions;There is no obvious statistical difference in biodynamics between the parallel and cross methods by the Fatigue and pulling out tests. We believe that there is no need to pursue absolute screw symmetry when parallel nailing can not be placed under some special circumstances.