Chinese Journal of Tissue Engineering Research ›› 2021, Vol. 25 ›› Issue (9): 1313-1317.doi: 10.3969/j.issn.2095-4344.4017

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Biomechanical analysis of different fixation methods of pedicle screws for thoracolumbar fracture

Xu Feng1, Kang Hui1, Wei Tanjun1, Xi Jintao2   

  1. 1Department of Orthopedics, General Hospital of Central Theater Command/Hubei Provincial Bone Trauma Treatment Research Center, Wuhan 430070, Hubei Province, China; 2Hubei 672 Orthopaedics Hospital of Integrated Chinese & Western Medicine, Wuhan 430061, Hubei Province, China
  • Received:2019-11-26 Revised:2019-11-29 Accepted:2020-05-16 Online:2021-03-28 Published:2020-12-15
  • Contact: Xi Jintao, Master, Hubei 672 Orthopaedics Hospital of Integrated Chinese & Western Medicine, Wuhan 430061, Hubei Province, China
  • About author:Xu Feng, MD, Chief physician, Department of Orthopedics, General Hospital of Central Theater Command/Hubei Provincial Bone Trauma Treatment Research Center, Wuhan 430070, Hubei Province, China
  • Supported by:
    the Training Program of Medical Science and Technology Youth in PLA, No. 18QNP054; the National Natural Science Foundation of China, No. 81401802

Abstract: BACKGROUND: Percutaneous fixation of thoracolumbral and lumbar fractures has been relatively mature, and there are many clinical fixation methods at present. However, due to the lack of a fixation method that can take the mechanical effect and operability into account, the clinical efficacy is different.  
OBJECTIVE: To study the biomechanical properties of lumbar vertebrae under the different kinds of pedicle screw fixation.
METHODS: Twenty-four cases of fresh multi-segment lumbar vertebrae of pigs were randomly divided into eight groups and modeled: groups A1 and A2 were fixed with six universal screws; groups B1 and B2 were fixed with four one-way screws and two universal screws; groups C1 and C2 were fixed with six uniplanar pedicle screw; groups D1 and D2 were fixed with four one-way screws. The biomechanics of eight groups was measured by universal testing machine. Four groups of A1, B1, C1 and D1 performed static experiments, while A2, B2, C2 and D2 performed fatigue experiments. 
RESULTS AND CONCLUSION: (1) All the four internal fixations could effectively fix lumbar fractures. The maximum load of the screw fixation at the fracture level was significantly higher in the screw placement group than that of unscrew placement group. Group C1 had the largest load, and group D1 had the smallest load, and there were significant differences among the four groups (P < 0.05). (2) Groups A1, B1, C1 and D1 conducted pressurized buttoning experiments, and the three groups B1, C1 and D1 all completed the buttoning experiments three times. The A1 group showed the slip of the nail tail when pressurized 300 N. The reduction effect of group C1 was better than that of groups A1, B1 and D1, and the difference was statistically significant (P < 0.05). The reduction effect of group B1 was better than that of groups A1 and D1, and the difference was statistically significant (P < 0.05). There was no significant difference in reduction effect between groups A1 and D1. (3) There was no significant difference in the anterior vertebral body height in groups B2, C2 and D2 after loading compared with that before loading. After loading, the anterior vertebral body height in group A2 was significantly lower than that before loading (P < 0.05). (4) All three kinds of pedicle screws can bear most of the stress of thoracolumbar vertebra, and the screw placement mode of injured vertebra can provide more effective stability and better shape recovery of injured vertebra. The effect of the uniplanar pedicle screw is better than that of the other three fixation screws.

Key words: bone, thoracic spine, lumbar spine, fracture, internal fixation, pedicle, screw, single plane, unidirectional screw, universal screw, biomechanics

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