Biomechanical investigation of traditional and modified cortical bone trajectory for osteoporosis lumbar spine - finite element analysis

Abstract

Abstract Background We aimed to investigate the biomechanical properties of the cortical bone trajectory (CBT) and modified cortical bone trajectory (MCBT) on the osteoporotic lumbar spine with the finite element method.Methods Four osteoporotic specimens were selected to establish the L4 vertebral body model. For the CBT, a screw with a diameter of 6.0 mm and a length of 35 mm was used, while for the MCBT, a screw with a diameter of 4.5 mm and a length of 40 mm was used. Two screws with different trajectories were inserted into the pedicles on the different sides of the same vertebral body. The axial pull-out strength, stability of the screw, and the stability of the vertebral body were compared.Results The pull-out strength of the MCBT (1620.00 ± 40.67N) was significantly higher than CBT (1360.25 ± 44.70N) (p < 0.001), and the stability of the MCBT screws in the upper, lower, left, and right direction was significantly higher than the CBT (p = 0.043; p = 0.027; p = 0.023; p = 0.035). The stability of the vertebral body with MCBT in axial rotation, and lateral bending was significantly higher than CBT (p = 0.005; p = 0.011). However, there was no significant difference in flexion and extension between the two groups (p > 0.05).Conclusion MCBT might be a choice for internal fixation of the lumbar spine in patients with osteoporosis.