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目的:研究第一骶后孔和骶外侧嵴与S2椎弓根的位置关系,建立以第一骶后孔和骶外侧嵴为解剖标志的S2椎弓根置钉定位技术。方法:取15具成人干燥骶骨标本,分别从S1、S2和S2、S3椎体融合遗迹(骶横线)处平行骶骨底平面截断骶骨,观察S2椎弓根的形态及第一骶后孔与椎弓根的关系;在平分S2椎弓根处平行骶骨底平面截断骶骨,观察S2椎弓根及其与骶外侧嵴的关系。在S2椎弓根前部(即盆面),平行骶骨底平分椎弓根的平面与骶前孔内侧缘连线的交点为a点,与正中矢状面的交点为b点。测量骶外侧嵴(s点)与a、b两点连线即sa线、sb线与正中矢状面夹角A角、B角及sa、sb的长度(sa和sb分别代表螺钉最小和最大长度,A角和B角分别代表螺钉在水平面上与正中矢状面的最小和最大夹角)。从椎管最外侧的一点P向sa线及sb线引垂线,与sa及sb的交点分别为h1和h2,测量Ph1和Ph2(螺钉最大半径)的长度。第一骶后孔下缘最低点(W)与第二骶后孔上缘最高点(Y)连线为WY,平分椎弓根的平面与WY线的交点为O(螺钉在骶骨后方进钉点),测量WO的距离,O点在W的下方时为正值,O点在W的上方时为负值。在10具成人尸体标本上观察骶骨前血管神经的毗邻关系,并按照上述的测量结果置入S2椎弓根螺钉,使螺钉穿出骶骨前方,观察螺钉的出钉点的位置。结果:S2椎弓根从后外走向前内,呈扇形,后宽前窄。WO的距离为0±1.42mm,椎弓根的中轴平面通过第一骶后孔下缘最低点W,经过两侧W点画一水平线,此线与两侧骶外侧嵴的交点可作为S2椎弓根置钉的进钉点,其进钉角度在矢状面上与骶骨底平行。A角平均为30.23°(27°～33°),B角平均为45.73°(40°～51°);sa平均为27.53mm(26.60～28.14mm),sb平均为35.46mm(34.84～36.04mm);Ph1平均为9.55mm(3.98～5.20mm),Ph2平均为4.53mm(3.94～5.10mm)。螺钉在水平面上与正中失状面夹角应为30.23°～45.73°;螺钉的长度为27.53～35.46mm;螺钉的直径只要小于2倍Ph2即可,即小于9.06mm。在骶骨前方骶交感干和骶正中动脉之间存在安全区域,尸体标本置入的20枚螺钉出钉点均位于此安全区域内。结论:第一骶后孔和骶外侧嵴与S2椎弓根间存在较恒定的解剖位置关系,第一骶后孔和骶外侧嵴可作为术中判断S2椎弓根位置和S2椎弓根置钉进钉点的解剖学标志。此种置钉方法的螺钉出钉点能落在骶骨前的安全区域。
OBJECTIVE: To study the relationship between posterior sacral foramina and sacral lateral crest and S2 pedicle, and to establish the S2 pedicle screw fixation technique based on anatomical landmark of posterior sacral foramen and lateral sacral sac. Methods: Fifteen adult patients with dry sacrum were taken and the sacrum was cut parallel to the sacral floor at the fusion site (sacral line) of S1, S2 and S2, S3 respectively. Morphology of S2 pedicle and the relationship between the first posterior sacral canal and Pedicle; in the bisector of the pedicle parallel to the sacral floor at the level of the sacrum cut off to observe the relationship between the S2 pedicle and the sacral lateral crest. In front of S2 pedicle (ie, basin), parallel to the bottom of the sacral vertebrae pedicle plane and sacral anterior connected to the medial edge of the intersection point of a point, and the median sagittal intersection point b points. Measuring the sacral lateral crest (s point) and a, b two points that the sa line, sb line and the median sagittal angle A angle, B angle and sa, sb length (sa and sb represent the minimum and maximum screw Length, angle A and angle B represent the minimum and maximum angles of the screw in the horizontal plane with respect to the median sagittal plane, respectively). From the outermost point of the spinal canal, point p to the sa and sb lines with a vertical line, and sa and sb intersect at h1 and h2, measuring Ph1 and Ph2 (the maximum radius of the screw). The lowest point of the inferior margin of the first posterior sacral hole (W) is connected with the highest point (Y) of the upper edge of the second sacral posterior hole (W), the intersection of the plane of the bisecting pedicle and the WY line is O Point), the distance of WO is measured, the point O is positive under W, and the point O is negative at the top of W. The adjacent relationship of anterior sacral anastomosis was observed on 10 adult cadaver specimens. The S2 pedicle screw was inserted into the anterior sacrum according to the above measurement results. The screw was observed out of the sacral anterior position. Results: The pedicle of S2 turned from anterior to posterior, fan-shaped and widened anteriorly and narrowly. WO distance of 0 ± 1.42mm, the central axis of the pedicle through the lower edge of the first sacral hole W the lowest point, drawn through a horizontal line on both sides of the W point, the line and the lateral sacral crest on both sides can be used as S2 vertebra Arch nail into the staple point, the angle of its into the sagittal plane parallel to the sacrum. The average angle of angle A was 30.23 ° (27 ° -33 °) and angle B was 45.73 ° (40 ° -51 °). The average sa was 27.53 mm (26.60-28.14 mm) and the average sb was 35.46 mm (34.84-36.04 mm) ); Ph1 average 9.55 mm (3.98 to 5.20 mm) and Ph2 average 4.53 mm (3.94 to 5.10 mm). The angle between the screw and the median lost plane should be 30.23 ° ~ 45.73 °; the length of the screw should be 27.53 ~ 35.46mm; the diameter of the screw should be less than 2 times Ph2, ie less than 9.06mm. Sacral sympathetic dry in front of the sacral anastomosis and the middle of the artery there is a safe area, the body specimens inserted 20 screws out of the nail point are located in this safe area. CONCLUSIONS: There is a relatively constant anatomical relationship between the posterior sacral foramina and the lateral sacral crest and the S2 pedicle. The first posterior sacral foramina and lateral sacral crest can be used as an intraoperative basis to determine the position of S2 pedicle and the position of S2 pedicle Anatomy of the nail into the nail point. The nailing method of screw out of the nail point can fall in the safe area before the sacrum.