Pedicle screw insertion angle and pullout strength: comparison of 2 proposed strategies

2011 ◽  
Vol 14 (5) ◽  
pp. 670-676 ◽  
Author(s):  
Serkan İnceoğlu ◽  
William H. Montgomery ◽  
Selvon St. Clair ◽  
Robert F. McLain
Keyword(s):  
Pedicle Screw ◽  
Vertebral Body ◽  
Screw Thread ◽  
Pullout Strength ◽  
Screw Insertion ◽  
Starting Point ◽  
Entry Points ◽  
Group A ◽  
Group B ◽  
Screw Group

Object Minimally invasive pedicle screws inserted vertically (that is, dorsoventrally) through the pedicle, as opposed to the more common coaxial technique, offer potential advantages by minimizing soft-tissue stripping during screw placement. The screws are designed for insertion through a medial starting point with vertical trajectory through the pedicle and into the vertebral body. As such, no lateral dissection beyond the insertion point is necessary. However, the effects of this insertion technique on the screw biomechanical performance over a short- and long-term are unknown. The authors investigated the pullout strength and stiffness of these screws, with or without fatigue cycling, compared with comparably sized, traditional screws placed by coaxial technique. Methods Twenty-one lumbar vertebrae (L-3, L-4, and L-5) were tested. Each pedicle of each vertebra was instrumented with either a traditional, coaxial pedicle screw (Group A), placed through a standard starting point, or a vertically oriented, alternative-design screw (Group B), with a medial starting point and vertical trajectory. The specimens were divided into 2 groups for testing. One group was tested for direct pullout (10 specimens) while the other was subject to pullout after tangential (toggle) cyclic loading (11 specimens). The screws were cycled in displacement control (± 5 mm producing ~ 4-Nm moment) at a rate of 3 Hz for 5000 cycles. Pullout tests were performed at a rate of 1 mm/minute. Results Two-way ANOVA showed that Group B screws with a medial starting point (2541 ± 1090 N for cycled vs 2135 ± 1323 N for noncycled) had significantly higher pullout loads than Group A screws with a standard entry point (1585 ± 766 N for cycled vs 1417 ± 812 N noncycled) (p = 0.001). There was no significant effect of cycling or screw insertion type on pullout stiffness. Tangential stiffness of the Group B screws was significantly less than that of the Group A screws (p = 0.001). The stiffness of both screws in the toe region was significantly affected by cycling (p = 0.001). Conclusions The use of Group B screws inserted through a medial starting point showed greater pullout load than a Group A screw inserted through a standard starting point. The greater pullout strength in Group B screws may be due to screw thread design and increased cortical bone purchase at the medial starting point. Nevertheless, anatomical considerations of the medial starting point, that is, pedicle or lateral vertebral body cortex breach, may limit its application. The medial starting point of the Group B screw was frequently in the facet at the L-3 and L-4 pedicle entry points, which may have clinical importance.

The morphology of proximal pole scaphoid fractures: implications for optimal screw placement

2017 ◽  
Vol 43 (1) ◽  
pp. 73-79 ◽  
Author(s):  
Timothy J. Luchetti ◽  
Youssef Hedroug ◽  
John J. Fernandez ◽  
Mark S. Cohen ◽  
Robert W. Wysocki
Keyword(s):  
Sagittal Plane ◽  
Fracture Line ◽  
Screw Thread ◽  
Proximal Pole ◽  
Screw Insertion ◽  
Scaphoid Fractures ◽  
Starting Point ◽  
Screw Length ◽  
Sagittal Image ◽  
The Ideal

The purpose of this study was to measure the radiographic parameters of proximal pole scaphoid fractures, and calculate the ideal starting points and trajectories for antegrade screw insertion. Computed tomography scans of 19 consecutive patients with proximal pole fractures were studied using open source digital imaging and communications in medicine (DICOM) imaging measurement software. For scaphoid sagittal measurements, fracture inclination was measured with respect to the scaphoid axis. The ideal starting point for a screw in the proximal pole fragment was then identified on the scaphoid sagittal image that demonstrated the largest dimensions of the proximal pole, and hence the greatest screw thread purchase. Measurements were then taken for a standard screw trajectory in the axis of the scaphoid, and a trajectory that was perpendicular to the fracture line. The fracture inclination in the scaphoid sagittal plane was 25 (SD10) °, lying from proximal palmar to dorsal distal. The fracture inclination in the coronal plane was 9 (SD16) °, angling distal radial to proximal ulnar with reference to the coronal axis of the scaphoid. Using an ideal starting point that maximized the thread purchase in the proximal pole, we measured a maximum screw length of 20 (SD 2) mm when using a screw trajectory that was perpendicular to the fracture line. This was quite different from the same measurements taken in a trajectory in the axis of the scaphoid. We also identified a mean distance of approximately 10 mm from the dorsal fracture line to the ideal starting point. A precise understanding of this anatomy is critical when treating proximal pole scaphoid fractures surgically.

PS01.152: BODY TEMPERATURE IN THORACOSCOPIC ESOPHAGECTOMY AND AIR CONDITIONING SYSTEM OF OPERATION ROOM

2018 ◽  
Vol 31 (Supplement_1) ◽  
pp. 92-93
Author(s):  
Hisashi Usuki ◽  
Takayoshi Kishino ◽  
Masao Fujiwara ◽  
Keiichi Okano ◽  
Yasuyuki Suzuki
Keyword(s):  
Body Temperature ◽  
Air Conditioning ◽  
Conflicts Of Interest ◽  
The Body ◽  
Thoracoscopic Esophagectomy ◽  
Air Conditioning System ◽  
Operation Room ◽  
Starting Point ◽  
Group A ◽  
Group B

Abstract Background It is well known that the perioperative hypothermia often cause the perioperative complications. In this study the hypothermia during the thoracoscopic esophagectomy and the relationship between the hypothermia and the air conditioning system of operation room were evaluated. Methods The subject of this study was 58 patients with esophageal cancer. Fifty of them were male and the others were female and the age was 65.2 + -8.4 years old. Forty three of 58 patients underwent the surgery in the old operation rooms (Group A) and 15 of them underwent it in the operation rooms with new air condirioning system (Group B). The 18 measuring points were picked up for each patient, which were from 10 to 180 minutes after start. The body temperatures were measured every 10 minutes after starting anesthesia. The temperature difference comparing with the starting point of surgery and the frequency of hypothermic state were evaluated. ‘Hypothermic state’ was defined that the temperature reduce more than 0.3 centigrade in comparison with the temperature at the starting point of surgery in this study. Results < 1 > The body temperature reduced early 60 minutes and then rose slowly. It reduce 0.22 + -0.35 centigrade at 60 minutes after starting surgery in comparison with the starting point of surgery. < 2–1 > The temperature of the patients in Group A reduced 0.24 + -0.03 centigrade and 0.32 + -0.09 centigrade at 30 and 60 minutes after starting surgery. But, the temperature of the patients in Group B reduced only 0.05 + -0.01 centigrade at 30 minutes after starting surgery and the temperature recovered at 60 minutes. These differences were statistically significant. < 2–2 > The total measuring points were 774 points in Group A and 270 points in Group B. The hypothermic state was observed 353 measuring points (45.6%) in Group A, and only 8 points (3.0%) in Group B. This difference was statistically significant. Conclusion The new operation rooms, in which the temperature of the air flow for the patients and that for surgeons can be set separately, is useful for keeping the body temperature of the patients adequately. Disclosure All authors have declared no conflicts of interest.

scholarly journals Which Surgical Method is More Effective in the Fifth Metatarsal Base Fracture?

2017 ◽  
Vol 2 (3) ◽  
pp. 2473011417S0002
Author(s):  
Jun-Beom Kim ◽  
Chi Ahn ◽  
Byeong-Seop Park
Keyword(s):  
Clinical Results ◽  
Plate Group ◽  
Group A ◽  
The Mean ◽  
The Difference ◽  
Group B ◽  
Clinical And Radiological Results ◽  
Mean Time ◽  
Screw Group

Category: Trauma Introduction/Purpose: The aim of this study was to evaluate and compare the clinical and radiological results of internal fixation with headless cannulated screw and locking compression distal ulna hook plate for the fracture at the base of fifth metatarsal bone, Zone 1. Methods: From April 2012 to April 2015, thirty cases (29 patients) were evaluated retrospectively. The mean follow up periods was 13 months. There were divided two groups based on use of the screw (group A, n=15) or the plate (group B, n=15).We measured the displacement to diastasis of the fracture on the foot oblique radiographs taken pre- and post-operatively in each group, checked the time to bone union and the difference of the reduction distance in each group. Clinical results were evaluated using American Orthopedic Foot and Ankle Society (AOFAS) midfoot score at 12 months postoperative. Results: In group A, the mean time to union was 54.2±9.3 days, the mean displacement to diastasis improved to 0.3±0.4 mm postoperatively (p<0.001), and the mean reduction distance was 2.9±1.0 mm. In group B, the mean time to union was 41.5±7.0 days, the mean displacement to diastasis improved to 0.06±0.2 mm postoperatively (p<0.001), and the mean reduction distance was 4.1±1.6 mm. AOFAS score was verified 97.7±3.4 in group A and 98.2±3.2 in group B. The time to union was significantly different between groups A and B (p=0.01).There were no complications. Conclusion: We suggest that the plate is more effective method for the shorter union time in surgical treatment of fifth metatarsal base fractures.

Biomechanical Effects of Lumbar Pedicle Screw Insertion Depth on Screw Loosening and Fulcrum Location

2013 ◽  
Author(s):  
Laura E. Buckenmeyer ◽  
Kristophe J. Karami ◽  
Ata M. Kiapour ◽  
Vijay K. Goel ◽  
Constantine K. Demetropoulos ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Pedicle Screws ◽  
Screw Loosening ◽  
Pullout Strength ◽  
Insertion Depth ◽  
Bone Implant ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Increased Risk ◽  
Screw Length

Osteoporosis is a critical challenge in orthopedic surgery. Osteoporotic patients have an increased risk of loosening and failure of implant constructs due to a weaker bone-implant interface than with healthy bone. Pullout strength of pedicle screws is enhanced by increased screw insertion depth. However, more knowledge is needed to define optimal pedicle screw insertion depth in relation to screw-bone interface biomechanics and the resulting loosening risk. This study evaluates the effects of screw length on loosening risk in the osteoporotic lumbar spine.

scholarly journals Biomechanical Study of Cortical Bone Trajectory Screws in Intervertebral Fixation of Lumbar Tuberculosis

2021 ◽  
Author(s):  
Chen-Wei Zhang ◽  
Shi-Yuan Shi ◽  
De-Xin Hu ◽  
Shen-Ping Hu ◽  
Jin-Ping Hu ◽  
...  
Keyword(s):  
Lumbar Spine ◽  
Internal Fixation ◽  
Bone Graft ◽  
Lateral Bending ◽  
Flexion Extension ◽  
Group A ◽  
Group B ◽  
Group D ◽  
State 1 ◽  
Screw Group

Abstract BackgroundWe aimed to explore the biomechanical stability and advantages of cortical bone trajectory (CBT) screws in the treatment of lumbar spine tuberculosis and provide biomechanical basis for the choice of clinical fixation methods. Methods16 pig spine specimens (T12-L5) were selected to simulate the lumbar spine(L2-L3) tuberculosis bone destruction model in vitro. The 16 specimens were randomly divided into 4 groups, and short segments (pedicle screws of the diseased vertebrae) were assigned respectively. Fixation (group A), short-segment fixation (group B), fixation with pedicle screw (group C), fixation with CBT screw (group D), 4 specimens in each group , Each specimen in each group was subjected to biomechanical testing in the state of complete specimen (state 1) and L2-3 spinal tuberculosis model bone graft fusion and internal fixation (state 2). Load each specimen on the spine 3D exercise machine, respectively apply moments of 2N·m, 2.5N·m, 1N·m, 3N·m, meanwhile record the movement of the specimens in the four directions of flexion，extension，lateral bending and torsion ROM, compare Simultaneously analyze each group of ROM. ResultsThe ROMs of flexion, extension, lateral bending, and torsion in group A in state 1 and state 3 modes were （8.47±1.76）°、 （7.01±1.10）°、 （5.03±0.92）°、 （4.48±0.41）°and （4.78±0.07）°、 （2.91±0.16）°、 （2.66±0.09）°、 （2.23±0.05）°; the ROMs of flexion, extension, lateral bending and torsion in group B in state 1 and state 3 modes were （7.32±0.75）°、 （5.35±0.69）°、 （3.44±0.51）°、 （3.36±1.02）°and（3.51±0.29）°、 （1.74±0.04）°、 （1.53±0.31）°、 （1.23±0.08）°; The ROMs of flexion, extension, lateral bending, and torsion in group C in state 1 and state 3 modes were （10.01±0.39）°、 （9.05±0.25）°、 （7.42±1.06）°、 （6.92±1.15）°and （7.21±0.17）°、 （5.07±0.02）°、 （5.12±0.74）°、 （4.58±0.01）°; The ROMs of flexion, extension, lateral bending, and torsion in group D in state 1 and state 3 modes were （9.20±1.37）°、 （7.38±0.88）°、 （6.89±1.22）°、 （6.00±0.52）°and （6.06±0.16）°、 （3.99±0.02）°、 （3.85±0.08）°、 （3.47±0.10）°. The ROM value of each fixed mode group under the state of bone graft fusion and internal fixation was lower than that of the intact state, and the difference was statistically significant (P<0.05)，The t values are 4.531, 5.346, 6.008, 4.149; 9.481, 16.181, 11.814, 4.769; 4.349, 8.002, 4.473, 4.800; 5.041, 4.146, 12.232, 10.58. ConclusionCBT screw disease intervertebral fixation can not only provide sufficient mechanical stability, but also provide stronger stability when using the same fixed segment, and The fixed segments are minimized.

scholarly journals Is cement-augmented sacroiliac screw fixation with partially threaded screws superior to that with fully threaded screws concerning compression and pull-out force in fragility fractures of the sacrum? – a biomechanical analysis

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Juliana Hack ◽  
Maiwand Safi ◽  
Martin Bäumlein ◽  
Julia Lenz ◽  
Christopher Bliemel ◽  
...  
Keyword(s):  
Screw Fixation ◽  
Fragility Fractures ◽  
Cement Augmentation ◽  
Osteoporotic Bone ◽  
Sacroiliac Screw ◽  
Pull Out ◽  
Sacroiliac Screw Fixation ◽  
Group A ◽  
Group B ◽  
Screw Group

Abstract Background Providing a stable osteosynthesis in fragility fractures of the pelvis can be challenging. Cement augmentation increases screw fixation in osteoporotic bone. Generating interfragmentary compression by using a lag screw also improves the stability. However, it is not known if interfragmentary compression can be achieved in osteoporotic sacral bone by cement augmentation of lag screws. The purpose of this study was to compare cement-augmented sacroiliac screw osteosynthesis using partially versus fully threaded screws in osteoporotic hemipelvises concerning compression of fracture gap and pull-out force. Methods Nine fresh-frozen human cadaveric pelvises with osteoporosis were used. In all specimens, one side was treated with an augmented fully threaded screw (group A), and the other side with an augmented partially threaded screw (group B) after generating a vertical osteotomy on both sides of each sacrum. Afterwards, first a compression test with fracture gap measurement after tightening of the screws was performed, followed by an axial pull-out test measuring the maximum pull-out force of the screws. Results The fracture gap was significantly wider in group A (mean: 1.90 mm; SD: 1.64) than in group B (mean: 0.91 mm; SD: 1.03; p = 0.028). Pull-out force was higher in group A (mean: 1696 N; SD: 1452) than in group B (mean: 1616 N; SD: 824), but this difference was not statistically significant (p = 0.767). Conclusions Cement augmentation of partially threaded screws in sacroiliac screw fixation allows narrowing of the fracture gap even in osteoporotic bone, while resistance against pull-out force is not significantly lower in partially threaded screws compared to fully threaded screws.

scholarly journals Pullout strength of adjusting pedicle screw with or without self-bone grafting in the previous trajectory using an osteoporotic human vertebral body

2020 ◽  
Author(s):  
Sen Liu ◽  
Jia Li ◽  
Hong-Yang Gao ◽  
Wei Wang ◽  
Wei Dong ◽  
...  
Keyword(s):  
Bone Mineral Density ◽  
Pedicle Screw ◽  
Bone Mineral ◽  
Vertebral Body ◽  
Bone Grafting ◽  
Control Group ◽  
Pullout Strength ◽  
Mineral Density ◽  
Horizontal Angle ◽  
Normal Angle

Abstract Objectives The aim of this study is to explore the pullout strength of adjusting pedicle screw with or without self-bone grafting in the previous trajectory using an osteoporotic human vertebral body. Methods Thirty vertebrae from six cadavers were collected and all of the vertebrae were divided into two groups according to bone mineral density: control group with normal bone mineral density; osteoporosis group with osteoporosis. The osteoporosis group was randomly and evenly divided into five subsamples according to direction of reinsert pedicle screw: the normal angle, sagittal angle, sagittal bone grafting, horizontal angle, horizontal bone grafting. Axial pullout strength testing of the pedicle screw was performed and the maximum axial pullout force (Fmax) was applied to analyse. Result The bone mineral density of the control group was 1.115±0.065 g/cm3, and the bone mineral density of the osteoporosis group was 0.678±0.055 g/cm3, presenting significantly different between the two group (P<0.001). Compared with the control group, the Fmax of the normal angle group was smaller (600.64±43.10 vs 1100.74±49.08 N, P<0.001). Compared with the normal angle group, the Fmax of the sagittal angle group (339.13±38.90 vs 600.64±43.10 N, P<0.001) and the horizontal angle group (342.06±33.01 vs 600.64±43.10 N, P<0.001) were smaller. The Fmax in sagittal bone grafting group was higher than that with non-implanted bone in primary screw canal (492.30±42.06 vs 342.06±33.01 N, P<0.001), and the Fmax of the horizontal bone grafting group was higher than that with non-implanted bone in primary screw canal (502.02± 50.26 vs 342.06±33.01 N, P<0.001). Conclusion The pullout strength of adjusting pedicle screw is seriously decreased in osteoporotic human vertebral body and self-bone grafting in the previous trajectory is an effective remedial measure.

scholarly journals Type 2 sclerotic Modic change affect fusion result in patients undergoing PLIF with pedicle screw instrumentation: a retrospective study

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Hao Li ◽  
Shou Chen ◽  
He-Yu Wei ◽  
Chuang-Ye Han ◽  
Fan-Yue Zeng ◽  
...  
Keyword(s):  
Retrospective Study ◽  
Pedicle Screw ◽  
Fusion Rate ◽  
Modic Change ◽  
Pedicle Screw Instrumentation ◽  
Bony Fusion ◽  
Group A ◽  
Group B ◽  
Fusion Efficiency

Abstract Background Bony fusion rate was significantly lower in patients with type 3 Modic change than patients with normal endplates. It is not known whether there are relevant differences in fusion efficiency among patients with type 2 sclerotic Modic change or non-sclerotic Modic change, or no Modic change. Methods A retrospective study contained 196 lumbar segments in 123 subjects undergoing posterior lumbar interbody fusion (PLIF) with pedicle screw instrumentation (PSI) to assess the effect of type 2 sclerotic Modic change on fusion efficiency. These endplates were allocated into groups A, B, and C, according to their Modic changes. Group A had endplates with type 2 Modic change and endplate sclerosis. Group B had type 2 Modic change without endplate sclerosis. Group C had neither Modic change nor endplate sclerosis. The presence of Modic change was determined by magnetic resonance imaging (MRI). Endplate sclerosis in type 2 Modic change was detected by computed tomography (CT) before the operation. We collected CT data 3 months to more than 24 months after operation in patients to assess bony fusion. Results Incidences of bony fusion were 58.8% in group A, 95.0% in group B, 94.3% in group C. The bony fusion rate was significantly lower in group A than in either group B or C. There was no significant difference between groups B and C. Thus, endplates with type 2 sclerotic Modic change had a lower fusion rate in patients undergoing PLIF with PSI. Conclusion Type 2 sclerotic Modic change could be an important factor that affects solid bony fusion in patients undergoing PLIF with PSI. CT may help diagnose endplate sclerosis in patients with type 2 change and inform the choice of the best site for spinal fusion.

scholarly journals Effects of different pedicle screw insertion depths on sagittal balance of lumbar degenerative spondylolisthesis, a retrospective comparative study

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Quan Zhou ◽  
Jun-xin Zhang ◽  
Yi-fei Zheng ◽  
Yun Teng ◽  
Hui-lin Yang ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Sagittal Balance ◽  
Screw Fixation ◽  
Degenerative Spondylolisthesis ◽  
Leading Edge ◽  
Pedicle Screw Fixation ◽  
Screw Insertion ◽  
Lumbar Degenerative Spondylolisthesis ◽  
Screw Group

Abstract Background Few reports to date have evaluated the effects of different pedicle screw insertion depths on sagittal balance and prognosis after posterior lumbar interbody and fusion (PLIF) in patients with lumbar degenerative spondylolisthesis (LDS). Methods A total of 88 patients with single-level PLIF for LDS from January 2018 to December 2019 were enrolled. Long screw group (Group L): 52 patients underwent long pedicle screw fixation (the leading edge of the screw exceeded 80% of the anteroposterior diameter of vertebral body). Short screw group (Group S): 36 patients underwent short pedicle screw fixation (the leading edge of the screw was less than 60% of the anteroposterior diameter of vertebral body). Local deformity parameters of spondylolisthesis including slip degree (SD) and segment lordosis (SL), spino-pelvic sagittal plane parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS) and lumbar lordosis (LL), Oswestry Disability Index (ODI), and Visual Analog Scale (VAS) for back pain of both groups were compared. Postoperative complications, including vertebral fusion rate and screw loosening rate, were recorded. Results Except that PI in Group S at the final follow-up was not statistically different from the preoperative value (P > 0.05), other parameters were significantly improved compared with preoperative values one month after surgery and at the final follow-up (P < 0.05). There was no significant difference in parameters between Group L and Group S before and one month after surgery (P > 0.05). At the final follow-up, SD, SL, LL, PT and PI-LL differed significantly between the two groups (P < 0.05). Compared with the preoperative results, ODI and VAS in both groups decreased significantly one month after surgery and at the final follow-up (P < 0.05). Significant differences of ODI and VAS were found between the two groups at the final follow-up (P < 0.05). Postoperative complications were not statistically significant between the two groups (P > 0.05). Conclusions PLIF can significantly improve the prognosis of patients with LDS. In terms of outcomes with an average follow-up time of 2 years, the deeper the screw depth is within the safe range, the better the spino-pelvic sagittal balance may be restored and the better the quality of life may be.

scholarly journals How to improve the safety of bicortical pedicle screw insertion in the thoracolumbar vertebrae: Analysis base on three-dimensional CT reconstruction of patients in the prone position

2020 ◽  
Author(s):  
Chao Xu ◽  
Qingxian Hou ◽  
Yanchen Chu ◽  
Xiuling Huang ◽  
Wenjiu Yang ◽  
...  
Keyword(s):  
Pedicle Screw ◽  
Prone Position ◽  
Vertebral Body ◽  
Supine Position ◽  
Three Dimensional ◽  
Vena Cava ◽  
Ct Reconstruction ◽  
Screw Insertion ◽  
Pedicle Screw Insertion ◽  
Significant Difference

Abstract Background: Through the comparison of three-dimensional CT reconstruction between the supine position and the prone position, the relative position of thoracolumbar great vessels and vertebral body was studied, and the shortest safe distance between them was measured to improve the safety of bicortical pedicle screw insertion and reduce the risk of vascular injury. Methods: Forty adults were selected to participate the research. Three-dimensional reconstruction of thoracolumbar (T9-L3) CT was performed in the prone position and the supine position. The relative distance between the Aorta/Inferior Vena Cava (IVC) and vertebral body was obtained as AVD/VVD respectively. The relative angle of the Aorta/ IVC and the vertebral body was calculated as ∠AOY/∠VOY. Self-controlled experiments were carried out in the prone and the supine positions, and the data obtained were analyzed using SPSS 22.0 statistical software. Results: The AVD of the prone position and the supine position was the shortest at T12 (3.18 ±0.68mm), but the difference was not statistically significant. The aorta of the T9-L3 segment was shifted from the anterolateral to the anteromedial. The ∠AOY of the other groups differed significantly between the prone and supine positions in all vertebrae except L1 (P < 0.05), and the aorta in the prone position was more anteromedial than that of supine position. With regard to VVD/∠VOY, there was no significant difference between the prone and supine positions (P≥0.05), and the minimum VVD of L3 segment is greater than 5.4mm. The IVC has no obvious mobility and is fixed in the range of 20 °~ 30 ° near the midline. Conclusion: When using bicortical anchoring of pedicle screws, it is safe to ensure that the protruding tips of the screw is less than 3mm. Due to the mobility of the aorta in different postures and individual differences in anatomy, the prone position CT can help doctors to make better preoperative plans and decisions.

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