Biomechanical Analysis of Cortical Bone Trajectory Screw Versus Bone Cement Screw For Fixation In Porcine Spinal Low Bone Mass Model

Abstract

Purpose: To compare the biomechanics of cortical bone trajectory screw(CBT) and bone cement screw(BC) in isolated porcine spinal low bone mass model.Method: Ten porcine spines with 3 segments were treated with EDTA decalcification. After 8 weeks, all the models met the criteria of low bone mass. Ten specimens were randomly divided into two groups, one group was implanted with CBT screw(CBT group) and the other group was implanted with bone cement screw(BC group).The biomechanical material testing machine was used to compare the porcine spine activities of the two groups in flexion, extension, bending and axial rotation, and then insertional torque, pull-out force and anti-compression force of two groups were compared. Independent-sample t test was used for comparison between groups.Result: Ten 3 segments porcine spine models with low bone mass were established, the bone mineral density of all models was lower than 0.75g/cm2. The flexion, extension, bending and axial rotation angle of CBT group and BC group respectively were 7.1±1.3°,4.3±0.8°,3.4±0.8°,6.8±0.7°and 6.4±0.8°, 4.5±0.5°, 3.5±0.5°, 6.8±0.8°, there was no significant difference between the two groups,P＞0.05.However, there were significant differences between the two groups and the control group,P＜0.01.The insertional torque of the CBT group and BC group respectively were 0.43±0.09N-m and 0.30±0.07N-m (P=0.03), and the screw pull-out force were 462.67±72.51N and 325.60±77.27N (P=0.021), respectively. There were significant differences between the two groups. The anti-compression forces between the two groups were 3561.81±522.7N and 3586.80±607.42N, respectively, and there was no significant difference between the two groups (P =0.946).Conclusion: The insertional torque and pull-out force of the CBT were higher than those of the BC in the isolated low bone porcine spine model, and the range of motion and anti-compression ability of model were similar between the two fixation methods.