Mechanical Analysis of a New Variable Diameter Screw Versus Cemented Pedicle Screws in Lumbar Spine
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Abstract:
Abstract: Objective To compare the mechanical performance of the modified cortical bone trajectory (MCBT) placement technique using a new variable diameter screw with that of the cement-augmented pedicle screw instrumentation (CAPSI) nailing technique in the lumbar spine using a finite element method. The mechanical performance of the cement-augmented pedicle screw instrumentation (CAPSI) technique in the lumbar spine was compared with that of the cement-augmented pedicle screw instrumentation (CAPSI) technique.Merthods Cementau- gmented pedicle screw instrumentation and modified cortical bone track instrumentation in the L4 vertebral body model were established by obtaining CT scan data from osteoporotic patients. The finite element method was used to compare the stability, screw axial pull-out force and lumbar spine mobility under four working conditions: upper, lower, left and right using different screw techniques. Results The axial pull-out force of the screws in the MCBT group was 25.3% higher than that of the CAPSI group; the load-displacement ratios of the screws in the MCBT group were 14.9%, 23.2%, and 19.1% higher than those of the CAPSI group under the lower, left, and right working conditions, respectively; the load-displacement ratios of the screws in the MCBT group were slightly lower than those of the CAPSI group in the upper working conditions, but the differences were not significant (P > 0.05); in the anterior and posterior flexion conditions, the lumbar spine mobility of the MCBT group was reduced by 13.3% and 2.5%, respectively, compared with that of the CAPSI group; in the left lateral bending, right lateral bending, and axial rotational conditions, it was improved by 69.1%, 74.6%, and 118.1%, respectively, compared with that of the CAPSI group, but the difference was not significant (P > 0.05). Conclusion MCBT was slightly better than CAPSI in axial resistance to extraction force, lower, left and right working conditions of screws, and stability of vertebral anterior drive, and slightly weaker than CAPSI in upper, left lateral curvature, right lateral curvature, and axial rotational working conditions.The results of the present study demonstrated that MCBT has certain advantages compared with CAPSI, and it provides a pre-basic foundation for the clinical application of MCBT in osteoporosis.
