Cementing the apical and terminal pedicle screw applied in osteoporotic spine with lumbosacral degenerative disease: A finite element analysis / 中国组织工程研究

ABSTRACT

BACKGROUND: Cement-augmented pedicle screw is an effective fixation for osteoporotic spine, and it is important to reduce the rate of cement leakage. OBJECTIVE: To evaluate the stability of cementing the apical and terminal pedicle screw applied in osteoporotic spine with lumbosacral degenerative disease by finite element analysis. METHODS: An intact finite element model of L2-5 segment was established by using CT scan data of one normal male volunteer. After verifying the validity of the intact model, the cementing apical and terminal pedicle screw and cement-augmented pedicle screw models of double/multi-level segment fixation were established, respectively. A 150 N vertical axial pre-load was imposed on the superior surface and a 10 N·m moment was applied on the superior surface along the radial direction to simulate six different physiological motions flexion, extension, left bending, right bending, left rotation, and right rotation. The different of range of motion, cage stress, and pedicle screw stress on fixed segments were compared between models. RESULTS AND CONCLUSION: (1) The validity showed that the range of motion of the intact model was similar to cadaveric studies in all directions. (2) The range of motion of cementing the apical and terminal pedicle screw group was slightly larger than that of cement-augmented pedicle screw group and the difference between the two groups was less than 0.15°. The two fixation methods could maintain the similar stability of the operation segment. (3) The difference of the cage stress and instrument stress was also small between the two groups. (4) These results suggest that compare with cement-augmented pedicle screw, cementing the apical and terminal pedicle screw can increase the approximate stability in double-level and multi-level segment fusion. The cementing the apical and terminal pedicle screw procedure may reduce the risk of cement leakage and patient costs, and offer a useful alternative to the cement-augmented pedicle screw procedure.