骶2椎弓根置钉的应用解剖学研究

Applied anatomy of the pedicle screw placement on 2nd sacrum vertebra

中文关键词:  S2  椎弓根  螺钉  解剖

英文关键词:Ｓacrum 2  Ｐedicle  Ｓcrew  Ａnatomic

中文摘要:

  【摘要】 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。

英文摘要:

  【Abstract】　Objective：To explore the relationship between the 2nd sacrum pedicle and the first posterior sacral foramen and to establish anatomic landmark and technique of 2nd sacrum pedicle screw placement based on the first posterior sacral foramen and lateral sacral crest.Method：15 dry sacrum specimens from human being were used and the sacrum segments between S1 and S2，S2 and S3 vestige were separated with the line paralleling to plane of sacrum bottom.Sacrum 2 pedicle shape and there surrounding structure were observed.Sacrum 2 pedicle was cut from the midline paralleling to the bottom of sacrum.The relations between pedicle and first posterior sacral foramen，lateral sacral crest were investigated.In the anterior edge of S2 vertebral pedicle（pelvic surface of sacrum），the intersection of cutting plane with medial marginal line of anterior foramen was defined as point a，the sagittal plane′s center was point b，and the lateral sacral crest point was s，the length of sa and sb were measured，the former represented the screw smallest length and the latter represented the maximum length.The angle between sa and sb at sagittal plane were defined as A and B respectively，A and B representing the smallest and biggest inclined angle in the horizontal plane respectively.The perpendicular line from neurocanal most lateral（point P） to the sa line and sb line were defined as h1 and h2 respectively，the length of Ph1 and Ph2 were measured，the diameter of screw smaller than 2 times of Ph2 lengths was regarded as safe.The line from the first posterior foramen lower end（W） to the second posterior foramen upper end（Y） was obtained.The intersection of equal division of S2 pedicle plane and the WY line was O，WO was measured.10 cadavers′ sacral anterior structure were observed，pedicle screws placement in 2nd sacrum was performed based on data acquired.Result：The S2 pedicle was fan-shaped，going from posterolaterally to anteromedially.The central axis plane of pedicle was rightly through the lowest point of the S1 posterior foramen.The pedicle of S2 sited at the point of intersection between lateral sacral crest and the line through lowest point of the bilateral S1 posterior foramen.The length and angle of screw was 27.53-35.46mm and 30.23°-45.73° respectively.The front of the sacrum in which the area between sympathetic stem and sacrum middle artery was a safe zone，where screws thread had no neurovascular risk.Conclusion：The anatomic relations between S2 pedicle and S1 posterior foramen is constant，which can be used as a landmark for anchoring S2 pedicle.The thread of screw is in safe zone.