Finite Element Analysis of an Improved Correction System for Spinal Deformity

Surgical treatment for spinal deformity aims to correct malformation, release the nerves, and reconstruct spinal stability. To explore and develop a new improved spinal correction system (ISCS) for clinical application, we studied the stability and biomechanical characteristics of the ISCS through finite element analysis and comparison of the ISCS with the pedicle screw and rod system (PSRS).

Using L1-L3 CT image data of a normal adult male lumbar spine for establishment of L1-L3 finite element model, we established posterior internal fixation models for a comparative finite element analysis of PSRS and ISCS. An axial load of 500 N and a moment of 10 N•m were applied to L1 to simulate flexion, extension, lateral bending, and axial rotation. Stress distribution characteristics, load sharing, strain bending stiffness and strain angle change of the models were measured.

In flection and extension directions, the maximum stress of the L2 vertebral body and the L1/2 and L2/3 discs in PSRS was less than that of ISCS. In lateral bending and axial rotation directions, the maximum stress between PSRS and ISCS was similar. However, the stress shielding rate of L2, L1/2, and L2/3 intervertebral discs in ISCS was significantly lower than that of PSRS. We also found that both models had similar angular displacement and maximum displacement in lateral bending direction, but PSRS had a lower angular displacement and maximum displacement in flection and extension directions. Finally, we showed that PSRS had similar angular displacement and a lower maximum displacement compared with ISCS in axial rotation, whereas ISCS had lower bending stiffness than PSRS in different directions.

ISCS can effectively fix spinal deformities compared to PSRS. ISCS provides a new option for orthopedic surgery treatment of scoliosis and, therefore, warrants further clinical studies in patients with other spinal deformities.