Chinese Journal of Tissue Engineering Research ›› 2021, Vol. 25 ›› Issue (12): 1858-1863.doi: 10.3969/j.issn.2095-4344.3788

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Stability of three-dimensional motion of spine with long-segment posterior fixation at different screw densities

Xue Jingbo, Li Zepeng, Wang Cheng, Ouyang Zhihua, Li Xuelin, Yan Yiguo, Wang Wenjun   

  1. Department of Spine Surgery, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan Province, China
  • Received:2020-06-09 Revised:2020-06-13 Accepted:2020-08-04 Online:2021-04-28 Published:2020-12-25
  • Contact: Wang Wenjun, MD, Chief physician, Department of Spine Surgery, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan Province, China
  • About author:Xue Jingbo, MD, Associate chief physician, Department of Spine Surgery, The First Affiliated Hospital of University of South China, Hengyang 421001, Hunan Province, China
  • Supported by:
    the Guiding Project of Clinical Medical Technology Innovation in Hunan Province, No. 2017SK50202 (to XJB); the Class B Project of Health and Family Planning Commission of Hunan Province, No. 20180154 (to XJB); the Key Scientific Research Project of Health and Family Planning Commission of Hunan Province, No. A2017016 (to YYG); the Project Planned by Science and Technology Department of Hunan Province, No. 2017SK4004 (to WWJ)

Abstract: BACKGROUND: Spinal posterior orthopedic pedicle screw internal fixation has become the most common clinical treatment for adolescent idiopathic scoliosis, but the use of high density nail placement can cause greater trauma and increase medical costs. 
OBJECTIVE: Using the six-degree-of-freedom joint robot, the biomechanical test of the pig spine with different posterior nail density was carried out to investigate the effect of different posterior nail density on the three-dimensional motion stability of the spine. 
METHODS: In eight pig spine specimens, the model of total pedicle screw fixation (100% fixation) was first prepared. Afterwards, the pedicle screws were reduced in turn. Pedicle screws of different densities were placed in turn (82%, 64%, and 36%). Finally, the spine without pedicle screw fixation was used as the blank control group. A six-degree-of-freedom joint robot was used to test the flexibility of each group of pig spine specimens in flexion position, lateral bending position and axial rotation position. 
Results and conclusion: (1) In flexion position and lateral bending position, there was no significant difference in range of motion of the spine specimens between the whole screw internal fixation group (100%) and the partial pedicle screw density group (82%, 64%, and 36%) (P > 0.05). (2) In the axial rotation test, the stability of axial rotation was significantly reduced in the 36% pedicle screw group compared to the total screw fixation group and the 82% and 64% pedicle screw fixation groups (P < 0.001). (3) When the 64% pedicle screw fixation group was added to the transverse connecting rod fixation, the range of motion of axial rotation of the spine specimen was significantly reduced (P < 0.05). (4) It is indicated that limited reduction of nail density of pedicle screws does not adversely affect the stability of posterior segment fixation.


Key words: spine, posterior approach, orthopedic, screw density, long segment fixation, internal fixation, biomechanics

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