Applied Anatomic Study Of The Sacral Screw Fixation For The Sacroiliac Joint

ObjectiveTo make out one optimal technique for sacral screw fixation for sacroiliac joint, we Study the anatomy structure of Chinese adult’s posterior pelvic ring. Then we perform the technique on five cadavers specimens and on the patients later, to evaluating a summarizing the sacral screw fixation technique. The content including:1. To understand the risk on the sacral screw fixation technique more by observe and measure the nerve and vessel around the pedicle front of S1and S2.2. To facilitate the accurate localization of entry site of the sacral screw on the posterior surface of the ilium and make sure the direction and length of the sacral screw,3.Perform sacral screw internal fixation technique on five antiseptic cadaver specimens, then adjust and reform the technique, which offer experiences and lessons for clinical application; Materials and MethodsSixteen antiseptic specimens of human pelvic ring were studied,32side of the sacroiliac joint and the following parameters were measured or evaluated including:2.1The shortest distance between Sacral1pedicle leading edge of the cortical bone and L4, L5,LST, S1nerve, the sacral sympathetic trunk, internal iliac artery and vein, iliolumbar artery and vein, the caudal lateral arteriovenvous. The shortest distance between Sacral1pedicle leading edge of the cortical bone and Nerves S1, S2nerve, obturator nerve, lumbosacral trunk, sacral sympathetic trunk, internal iliac artery and vein, the superior gluteal artery and vein, the caudal lateral arteriovenous.2.2Then cut the S1pedicle through the narrowest region, and drill in through the center of the transverse section according to the right angle, the point drilled out is considered to be the optimal entrypoint on the outer table of the ilium. This point seen as the best needle point of S1screw (A).Reseat the pelvic ring, drill in through the outer entry point until to the contrary anterior cortex of S1vertebral body. Then to deal Sacral2pedicle with the same method, the point drilled out through the sacral2pedicle seen as the optimal entry point of S2screw(C). The measurements including:①the pedicle height of the first and second sacral vertebra(S1and S2);(②the pedicle width of S1and S2;③the angle between the pedicle and ventral plane of S1and S2,④the cephalad angle between the pedicle and parietal plane of S1and S2;the Vertical distance and horizontal distance of the entry point to posterior superior iliac spine; the distance from entry point to sacrum vestibule anatomy of S1and S2; the distance from entry point to contrary anterior cortex of S1and S2ertebral body, considered to be screw length of S1and S2.2.3We perform the operation of sacral screw fixation on five antiseptic cadaver specimens, then assessed the position of screw by cut the bone along the road of screw.ResultThe shortest distance from the Vessels and Nerves to the vertebral pedicle bone cortex of S1are following:the L4is,L5is0mm,LST is0.36±0.86mm, obturator nerve is7.08±1.24mm,the S1is5.07±0.89mm,the sacral sympathetic trunk is2.44±0.87mm, the intemal iliac artery and vein is6.50±1.54mm and4.04±0.96mm,the iliolumbar arrtery and vein is4.48±1.91mm and6.50±1.54mm,the lateral sacral artery and vein3.52士2.21mm and3.80±2.06mmThe shortest distance from the Vessels and Nerves to the vertebral pedicle bone corrtex of S2are following:the S1is0mm,the S2is4.31±1.41mm,the obturator nerve is27.04±6.34mm,the LST is7.73±2.27mm,the sacral sympathetic trunk is2.15±O.65mm, the intemal iliac artery and vein is13.76±6.12mm a and9.49±4.88mm,superior gluteal artery and vein is9.55±4.13mm and11.94±4.88mm,the lateral sacral artery and vein is2.55士1.39mm and3.09±1.64mm.The man data are following:the pedicle height of the first and second sacral(S1and S2)is22.20±1.62mm and16.70士1.24mm；the pedicle width of S1and S2is24.10±1.90mm and19.09±2.27mm:the horizontal and Verrtical di stance of the entry point of S1to posterior superior iliac spine is11.48±2.28mm and30.52±1.40mm,and the S2is11.97±1.54mm and19.40±2.14mm；the distance f-rom entry point to contrary anterior cortex of S1and S2vertebral body is81.35±2.23mm and62.91±4.11mm,the distance from entry point to sacrum vestibule anatomy of S1and S2is43.80±1.82mm and39.71±2.21mm；the cephalad angle between the pedicle and parietal plane of S1and S2is14.1±3.2.and7.7±1.6.；the angle between the pedicle and ventral plane of S1and S2is26.6±2.5.and24.0±2.3°.The female data are following:the pedicle height of the first and secornd sacral is20.32±1.77mm and13.72±1.57mm；the pedicle width of S1and S2is 22.41±2.02mm and15.81±1.55mm;the horizontal and Vertical distance of the entry point of S1to posterior superior iliac spine is8.81±1.19mm and32.80±1.84mm, and the entry point of S2to posterior superior iliac spine is9.59±1.36mm and25.802.17mm; the distance from entry point to sacrum vestibule anatomy of S1and S2is40.72±1.91mm and36.71±1.89mm; the distance from entry point to contrary anterior cortex of S1and S2vertebral body is70.19±2.21mm and60.33±2.35mm, considered to be screw length of S1and S2;the cephalad angle between the pedicle and parietal plane of S1and S2is14.1±2.5°and7.5±1.9°;the angle between the pedicle and ventral plane of S1and S2is29.8±2.2°and26.3±1.7°.The result of sacral screw fixation on3cadaver with15screw according to the entry point and direction in the study was that there were no screw penetrate pedicle of S1and S2or sacral vertebralbody.Conclusions3.1The male parameters of S1and S2are following:the horizontal of the entry point to posterior superior iliac spine is11.5mm and12.0mm, and the vertical distance is30.5mm and19.5mm; the cephalad angle is14°and7.5°; the angle between the coronal plane is26°and24°;the length of screw is80mm and60mm the diameter of the screw is6.5mm.3.2The female parameters of S1and S2are following:the horizontal of the entry point to posterior superior iliac spine is8.8mm and9.6mm, and the vertical distance is32.8mm and25.8mm; the cephalad angle is14°and7.5°; the angle between the coronal plane is30°and26°;the length of screw is70mm and55. mm the diameter of the screw is6.5mm3.3The screw inserted on S1is more safe than S2 3.4The L4, L5, S1, LST, lateral sacral artery and vein,and the iliolumbar artery and vein are easy injuryed in the posterior pelvic ring with the posterior pelvic ring3.5The technique of sacral screw fixation with pedicle of S1and S2has the advantage of small trauma quickly recovery and little cost, which will take a leading role in treatment for injury of posterior pelvic ring.