Li Changqing, Zhou Yue, Wang Hongwei, Liu Jun, Xiang Liangbi
Department of Orthopedics, Xinqiao Hospital, the Third Military Medical University, Chongqing, China.
Department of Orthopedics, General Hospital of Shenyang Military Area Command of Chinese PLA, Shenyang, Liaoning, China.
PLoS One. 2014 Jun 10;9(6):e99156. doi: 10.1371/journal.pone.0099156. eCollection 2014.
To compare the von Mises stresses of the internal fixation devices among different short segment pedicle screw fixation techniques to treat thoracic 12 vertebral fractures, especially the mono-segment pedicle screw fixation and intermediate unilateral pedicle screw fixation techniques.
Finite element methods were utilised to investigate the biomechanical comparison of the four posterior short segment pedicle screw fixation techniques (S4+2: traditional short-segment 4 pedicle screw fixation [SPSF]; M4+2: mono-segment pedicle screw fixation; I6+2: intermediate bilateral pedicle screw fixation; and I5+2: intermediate unilateral pedicle screw fixation).
The range of motion (ROM) in flexion, axial rotation, and lateral bending was the smallest in the I6+2 fixation model, followed by the I5+2 and S4+2 fixation models, but lateral bending was the largest in the M4+2 fixation model. The maximal stress of the upper pedicle screw is larger than the lower pedicle screw in S4+2 and M4+2. The largest maximal von Mises stress was observed in the upper pedicle screw in the S4+2 and M4+2 fixation models and in the lower pedicle screw in the I6+2 and I5+2 fixation models. The values of the largest maximal von Mises stress of the pedicle screws and rods during all states of motion were 263.1 MPa and 304.5 MPa in the S4+2 fixation model, 291.6 MPa and 340.5 MPa in the M4+2 fixation model, 182.9 MPa and 263.2 MPa in the I6+2 fixation model, and 269.3 MPa and 383.7 MPa in the I5+2 fixation model, respectively. Comparing the stress between different spinal loadings, the maximal von Mises stress of the implants were observed in flexion in all implanted models.
Additional bilateral pedicle screws at the level of the fracture to SPSF may result in a stiffer construct and less von Mises stress for pedicle screws and rods. The largest maximal von Mises stress of the pedicle screws during all states of motion were observed in the mono-segment pedicle screw fixation technique.
比较不同短节段椎弓根螺钉固定技术治疗胸12椎体骨折时内固定装置的冯·米塞斯应力，尤其是单节段椎弓根螺钉固定技术和中间单侧椎弓根螺钉固定技术。
采用有限元方法研究四种后路短节段椎弓根螺钉固定技术（S4+2：传统短节段4枚椎弓根螺钉固定[SPSF]；M4+2：单节段椎弓根螺钉固定；I6+2：中间双侧椎弓根螺钉固定；I5+2：中间单侧椎弓根螺钉固定）的生物力学差异。
I6+2固定模型在屈曲、轴向旋转和侧方弯曲时的活动度（ROM）最小，其次是I5+2和S4+2固定模型，但M4+2固定模型在侧方弯曲时的活动度最大。在S4+2和M4+2中，上位椎弓根螺钉的最大应力大于下位椎弓根螺钉。在S4+2和M4+2固定模型中，上位椎弓根螺钉观察到最大的冯·米塞斯应力，而在I6+2和I5+2固定模型中，下位椎弓根螺钉观察到最大的冯·米塞斯应力。在S4+2固定模型中，椎弓根螺钉和棒在所有运动状态下的最大冯·米塞斯应力值分别为263.1MPa和304.5MPa；在M4+2固定模型中分别为291.6MPa和340.5MPa；在I6+2固定模型中分别为182.9MPa和263.2MPa；在I5+2固定模型中分别为269.3MPa和383.7MPa。比较不同脊柱负荷下的应力，所有植入模型在屈曲时观察到植入物的最大冯·米塞斯应力。
在SPSF基础上，在骨折节段增加双侧椎弓根螺钉可能会使内固定结构更坚固，椎弓根螺钉和棒的冯·米塞斯应力更小。在所有运动状态下，单节段椎弓根螺钉固定技术观察到椎弓根螺钉的最大冯·米塞斯应力最大。
