| Objective:To investigate the feasibility of posterior pedicle screw insertion in the subaxial cervical spine guided by safe core-referred,and further verified by a cadaver specimen study.Methods:（1）60 cases of adult cervical spine CT data and 60 cases of X-ray standard anteroposterior and lateral image data（including 30 males and 30 females）were collected.The original Dicom data of CT were imported into Mimics 21.0 software.The safe core and virtual pedicle screw path of C3-C7were constructed according to the self-designed"subaxial cervical pedicle screw path virtual construction method"assisted by software,and the pedicle screw insertion was simulated with a 3.5 mm diameter cylindrical tool under the control of the safe core.At the same time,data were recorded:（1）the effectiveness of constructing the safe-core（including the effective rate of constructing the safe-core,the coincidence rate between the virtual pedicle screw path and the safe-core,and the coincidence rate between the intersection of the diagonal tangent line of the channel and the safe-core）;（2）the basic parameters of the safe-core（including the length,width,and height of the safe-core）and the virtual pedicle screw path parameters under the control of the safe-core（the minimum abduction angle,maximum abduction angle,maximum head inclination angle,and maximum tail inclination angle of the virtual pedicle screw path,the average distance from the cortex of the screw entry area to the center point of the safe-core,and the projection area of the screw entry area）;（3）the spatial position relationship between the center point of the safe-core and the vertebral body（the vertical distance from the center point of the safe-core to the apex line of the outer edge of the uncovertebral joint,and the vertical distance from the center point of the safe-core to the posterior wall line of the vertebral body）.（2）12 specimens of cadaver subaxial cervical spine were collected for simulated screw insertion.The left side of the specimen was set as the experimental group and nails were placed with safe core-referred;the right side of the specimen was set as the control group and nails were placed with the"Abumi’s traditional free-hand screw insertion".CT scans were performed during and after the experiment to determine the qualified rate of screw path preparation and the accuracy of screw insertion in the experimental group and the control group.The qualified rate of screw path preparation was judged by whether the screw path in the anterior segment of the experimental group was in the safe nucleus area,and whether the screw path in the whole course of the control group was in the pedicle channel;the accuracy of screw insertion was judged by whether the screws in the two groups broke through the pedicle cortex（grade 0,the screws did not break through the pedicle cortex;grade I,0mm>the screws broke through the pedicle cortex≤1 mm;grade II,the screws broke through the pedicle cortex>1 mm;grade 0 and grade I were judged as accurate screw insertion,and grade II was inaccurate）.Results:（1）The feasibility study of the reference method of"safe-core of screw path"showed that the total effective rate of constructing the safe-core of C3-C7was 97.00%（291/300）;the coincidence rate between the virtual pedicle screw path of C3-C7and the safe-core was 100.00%;and the coincidence rate between the diagonal tangent intersection of C3-C7channel and the safe-core was 100.00%.The length of the safe-core C3-C7was uniformly set as 3.50 mm;the width of the safe-core:C3was（3.62±0.88）mm,C4was（3.98±0.80）mm,C5was（4.46±0.68）mm,C6was（4.91±0.68）mm,and C7was（5.67±0.77）mm;the height of the safe-core:C3was（4.97±0.96）mm,C4was（5.29±1.16）mm,C5was（5.52±0.67）mm,C6was（5.64±0.73）mm,and C7was（6.35±0.65）mm;Abduction angle range of virtual pedicle screw Path:C3was（28.94±7.04）°～（67.37±6.49）°,C4was（29.08±5.30）°～（70.55±5.87）°,C5was（26.24±4.38）°～（72.65±2.50）°,C6was（24.69±3.89）°～（70.66±2.61）°,C7was（20.59±5.30）°～（64.27±2.92）°;craniocaudal inclination angle range of virtual Pedicle screw Path:C3was cephalic inclination（14.75±4.40）°～caudal inclination（10.65±4.36）°,C4was cephalic inclination（17.61±4.35）°～caudal inclination（8.71±4.34）°,C5was cephalic inclination（16.99±3.22）°～caudal inclination（11.93±3）°.82)°,C6was cephalic inclination（19.27±2.87）°～caudal inclination（10.36±3.37）°,C7was cephalic inclination（23.05±3.16）°～caudal inclination（9.37±3.63）°;the mean distance from the cortex of the entry area to the center point of the safe-core was（11.82±0.89）mm for C3,（11.15±0.90）mm for C4,（12.01±0.90）mm for C5,（12.51±0.96）mm for C6,and（11.00±1.04）mm for C7;the projection area C3of the entry area was（41.56±14.73）mm2,（42.87±12.89）mm2for C4,（44.80±9.30）mm2for C5,（50.98±11.51）mm2for C6,and（55.07±9.90）mm2for C7.The vertical distance from the center of the safe-core to the apex of the outer edge of the uncovertebral joint was（0.84±0.57）mm for C3,（0.74±0.54）mm for C4,（0.83±0.84）mm for C5,（1.10±0.74）mm for C6,and（0.96±1.01）mm for C7;the vertical distance from the center of the safe-core to the Posterior wall of the vertebral body was（2.08±0.41）mm for C3,（2.34±0.60）mm for C4（2.41±0.73）mm for C5,（2.01±0.89）mm for C6,and（0.34±1.19）mm for C7.（2）The experimental results showed that 60 screw channels were prepared in the experimental group and the control group,and the qualified rate of screw channel preparation was 100%.Sixty screws were placed in the experimental group and the control group,including 52 screws in grade 0,7 screws in grade I,and 1 screws in grade II in the experimental group,with an accuracy of 98.30%;45 screws in grade 0,7 screws in grade I,and 8 screws in grade II in the control group,with an accuracy of86.70%（P<0.05,difference statistically significant）.Conclusion:The application of Mimics 21.0 software in the construction of subaxial cervical spine safe core and virtual pedicle screw path has a high effective rate,and the image characteristics and spatial position of safe core are stable,which can be transformed into non-solid imaging anatomical landmarks that are easily identified on two-dimensional X-ray images.The safe core can be used as a reference guide screw insertion during screw insertion in actual subaxial cervical spine specimens,and the recognition rate is as high as 100%.Compared with Abumi’s traditional free-hand screw insertion,safe core-referred guided screw insertion has a higher success rate in specimen experimental studies.This study provides a new idea for the improvement of pedicle screw technique in the subaxial cervical spine.It lays a foundation for the further clinical application of posterior pedicle screw insertion in the subaxial cervical spine guided by safe core-referred. |
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