Biomechanical Analysis of Cortical Bone Trajectory Screw Versus Bone Cement Screw for Fixation in Porcine Spinal Low Bone Mass Model

A prospective study of in vitro animal. OBJECTION: To compare the biomechanics of cortical bone trajectory screw (CBT) and bone cement screw (BC) in an isolated porcine spinal low bone mass model. SUMMARY OF BACKGROUND DATA: The choice of spinal fixation in patients with osteoporosis remains controversial. Is CBT better than BC? Research on this issue is lacking. METHODS: 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 groups, 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 the 2 groups were compared. Independent sample t test was used for comparison between groups. RESULTS: Ten 3 segments of porcine spine models with low bone mass were established, and the bone mineral density of all models was lower than 0.75 g/cm(2). There is no difference between the CBT and BC groups in flexion, extension, bending, and axial rotation angle, P>0.05. However, there were significant differences between the 2 groups and the control group, with P＜0.01. The 2 groups significantly differed between the insertional torque (P=0.03) and the screw pull-out force (P=0.021). The anti-compression forces between the 2 groups have no significant difference between the two groups (P=0.946). CONCLUSIONS: 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. The range of motion and anti-compression ability of the model was similar between the 2 fixation methods.