The Feasibility Analysis Of Sacroiliac Screw Director Through Pedicle Orientation

Objective: To explore feasibility of screw placement by the pedicle positioning throughthe special anatomical relationship between S1pedicle and lateral mass, provide experimentalevidence and theoretical basis for the application of screw placement by the pediclepositioner.Methods:1、100normal adult pelvises (male and female were50cases each) weremeasured by CT imaging.(1) Conventional measurement:①the S1transverse and sagittaldiameter;②the height of S1front and rear edge;③the width of the narrowest point in thehorizontal and coronal plane;④the area of the narrowest sacroiliac channel in the sagittalplane;⑤t he length of sacroiliac channel axis in the horizontal plane;⑥the distance betweenthe center of S1and lateral positioning point.(2) When positioning at the center and lateralpoint of S1,①t he maximum and minimum nail-entry angle in the horizontal plane;②themaximum and minimum nail-entry angle in the coronal plane;③t he range of nail-entry anglein the horizontal and coronal plane;④the angle of axis in the horizontal and coronal plane.2、The director, designed by data analysis, was used to place pedicle screw in the AO standardanalog pelvis (5dry pelvises and10cases of sacroiliac joint).Results:1(1) There were significant differences between men and women in "the S1transverse and sagittal diameter,"the height of S1front and rear edge",“the width of thenarrowest point in the horizontal plane”, and the area of the narrowest sacroiliac channel inthe sagittal plane. The mean of males were larger than females, indicating the S1volume andsacroiliac channels of males were larger than females;(2) there was no significant differencebetween safe angle of screw placement;(3) the measured indicators in the lateral point of S1were greater than in the center point of S1. The nail-entry range was safe and reliable to locatein the S1lateral point, according to the positioning of S1vertebral center point;(4)In the malespecimens: the needle angle in the horizontal plane, maximum:93.65°±7.73°, minimum: 76.71°±4.60°, with a safe range of16.93°±6.14°for pedicle screw placement; the needleangle in the coronal plane, maximum:92.16°±6.84°, minimum:65.05°±3.80°, with asafe range of27.11°±7.18°for pedicle screw placement. Female specimens: the needle anglein the horizontal plane, maximum:95.69°±4.98°, minimum:78.09°±3.72°, with a saferange of17.60°±2.74°for pedicle screw placement; the needle angle in the coronal plane,maximum:94.24°±5.05°, minimum:65.96°±4.74°, with a safe range of28.28°±6.12°forpedicle screw placement.2, The director, designed by data analysis, was successfully used toplace pedicle screw in10cases of sacroiliac joint, no screws were poorly located, or fail.Conclusion: The screw placement by the pedicle positioning was safe and feasible. Itwas simple to place pedicle screw by director, and the indications and contraindications werethe same as traditional pedicle screw way. The director could be used to patients unsuitablefor traditional pedicle screw, such as greater next angle of sacrum lateral mass, narrowsacroiliac channel, if there was enough space for screws. The director has not yet formallyapplied to the clinical, and the specific application experience needs to be further accumulatedin the late-stage study.