骶2椎弓根前外侧置钉法的应用解剖学研究

Anatomy study of the pedicle screw placement anterolaterally on S2 vertebra

中文关键词:  骶2  椎弓根  内固定  解剖学

英文关键词:S2  Pedicle  Internal fixation  Anatomy

中文摘要:

  【摘要】 目的：观察S2椎弓根的解剖特点及与周围血管神经的毗邻关系，探讨以第一骶后孔与骶外侧嵴为解剖标志的S2椎弓根前外侧置钉技术的可行性。方法：取20具成人干燥骶骨标本，其中15具分别从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；在第一骶后孔下缘最低切迹处平行骶骨底平面截断骶骨。在S2椎弓根前部（即盆面），截面与骶前孔外侧缘连线的交点为A点，与耳状面前缘（即骶髂关节处）的交点为B点。在截面上测量骶外侧嵴（X点）与A、B两点连线即XA线、XB线长度及其与正中矢状面夹角α角、β角；在截面上测量骶中间嵴（Y点）与A、B两点连线即YA线、YB线长度及其与正中矢状面夹角γ角、θ角；在5具完整的干燥骶骨标本上于X点向前外侧置入椎弓根螺钉，置钉方法为矢状面平行骶骨底，角度在α角与β角之间，并行CT扫描观察螺钉的位置。在10具经福尔马林浸泡固定的成人尸体标本上观察骶骨前血管神经的毗邻关系，观察骶前孔、骶髂关节与骶前交感干、髂内动静脉的关系。并按照上述测量结果分别在X、Y点向前外侧置入S2椎弓根螺钉，使螺钉穿出骶骨前方，落在骶前孔外侧缘与耳状面前缘之间。观察螺钉的出钉点与骶前血管神经的关系。结果：S2前方有大量的骨质可供螺钉置入。XA为26.0±1.７mm，XB为33.１±1.1mm，α角为22.1°±２．０°，β角为36.0°±3.7°；YA为30.１±0.8mm，YB为35.5±１．０mm，γ角为36.7°±1.５°，θ角43.８°±1.3°。在骶髂关节前方从骶前孔外侧缘开始向外侧依次有髂内静脉、髂内动脉、髂外静脉、髂外动脉。第1骶前孔与第2骶前孔之间的前外侧有S1神经通过。骶前交感干走形在骶前孔内侧缘，出钉点在骶前孔外侧，髂内动静脉后方。结论：S2椎弓根前外侧置钉安全可行，向前外侧固定时螺钉不能突破前方骨皮质，以免伤及骶前血管及神经。以骶外侧嵴与第一骶后孔下缘最低切迹水平面交点（X点）为进钉点，前外侧置钉更适用。

英文摘要:

  【Abstract】 Objective：To investigate the S2 pedicle anatomy and determine the anatomic landmark and technique of S2 pedicle screw anterolateral placement associated with S1 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 parallel to plane of sacrum bottom.The profile of S2 pedicle was observed.S2 pedicle was cut from the first posterior foramen lower edge parallel to the bottom of sacrum.In the anterior edge of S2 pedicle（pelvic surface of sacrum），the intersection between cutting plane and lateral marginal line of anterior foramen was defined as point A，and the ear-shaped front edge（the sacroiliac joints） of the intersection was defined as point B.The lateral sacral crest point was defined as X，and the length of XA and XB representing the minimum and maximum length of the screw was measured respectively.The angles between XA and sagittal plane，ＸＢ　ａｎｄ　ｓａｇｉｔｔａｌ　ｐｌａｎｅ were defined as α and β respectively，which represented the minimum and maximum inclined angle in the horizontal plane respectively.In this plane，the middle sacral crest was defined as point Y，which was the same ａｓ X，the YA，YB，γ and θ angles wｅｒｅ measured.Pedicle screws were placed anterolaterally in 5 dry specimens，with the sagittal planｅ parallel to the sacral bottom and with the angle between α and β.CT scan was used to detect the site of screws.In 10 adult cadavers，the relationship between pre-sacral blood vessel and nerve and pre-sacral foramen，sacroiliac joint and pre-sacral sympathetic trunk，the iliac artery and vein were investigated.According to the above-mentioned results，S2 pedicle screws were placed in X and Y point.The tip of the screw and its relationship with pre-sacral neurovascular were also investigated.Result：Space was available for S2 screw placement，and XA was 26.0±1.7mm，XB was 33.1±1.1mm，α angle（22.1±2.0）°，β angle（36.0±3.7）°；YA was 30.１±0.8mm，YB was 35.5±１．０mm，γ angle was 36.7°±1.５°，θ angle was 43.８°±1.3°。In front of the sacroiliac joint，from the lateral border of the anterior sacral foramen，there sited the internal iliac vein，internal iliac artery，external iliac vein，external iliac artery respectively.In this region，S1 nerve root passed through.Pre-sacral sympathetic trunk located ｉｎ　the inside edge of pre-sacral foramen，and the tip of screws located behind the iliac artery and vein，and also laterally in anterior sacral foramen.Conclusion：S2 pedicle screw placement anterolaterally is feasible and safe，the front cortical bone should not be penetrated to avoid the injury to sacral vｅｓｓｅｌ and nerve root.X point can be used as entrance point.