Applied Anatomical Study On Technique Of Pedicle Screw Placement In Atlas

Objective: Atlas pedicle anatomy to measure, more in-depthunderstanding of their anatomy, and provide clinically relevant data to helpchoose the right pedicle screw.Meanwhile, Atlas accurate entry points selected,find the constant reference system into the nail and nail into the direction ofmeasurement and the angle between the selected reference system to determinethe most appropriate direction into the screw, as a Atlas pedicle screw set intothe guidelines.Methods: Jilin University Department of Anatomy, House, provided a fullset of20specimens of cervical dried bone (excluding deformities, fracturesand pathological destruction of specimens.)Specimens, regardless of gender,age, height, weight and so on.Whichever is Atlas20vertebrae specimens.Onboth sides of20specimens were hand pedicle into snails. The point which isprojection of internal and external margin midpoint below lateral mass of atlason the posterior arch is entrance point of screw. The sagittal is decided byinternal and external margin of ventral of above lateral mass of atlas andentrance point of screw A，Sagittal traverse atals lateral up and down margin，its midpoint is the penetration point B.Select the appropriate diameter andlength of the screw, along the direction of the axis into the pedicle so that thepedicle screw axis and the axis of overlap (along the horizontal or sagittalpedicle sawn specimens can be seen at the screw in the pedicle axis.)Removethe screws and Kirschner wires instead of screws inserted in the axis of thescrew channel, use the protractor measurement: the screw axis in the horizontalplane and median plane forming the horizontal angle (X angle); screw axis inthe sagittal plane and the plane of Atlas formed by the side of the vertical angle (Y horn).Using vernier caliper and straightedge measurements: the height ofposterior arch at the thinnest part of the vertebral artery groove (h); the widthof posterior arch at the thinnest part of the vertebral artery groove (w); thedistance from entrance point of screw to median plane(S1);the whole lengthscrew path (AB)；the distance between the internal and external margin ofdorsal of below lateral mass of atlas（S2）。Statistical analysis of data usingSPSS software.Results:(1) the width is greater than the height of posterior arch at thethinnest part of the vertebral artery groove (w>h), the t test has difference (P<0.05);(2)the distance from entrance point of screw to median plane(S1=21.2±3.5mm);(3)the whole length screw path (AB=26.1±4.4mm)；(4)thedistance between the internal and external margin of dorsal of below lateralmass of atlas（S2=11.1±1.1mm）(5) atlas horizontal angle (X) are10.9°±5.2°;vertical angle (Y) were4.1°±0.7°.Conclusion: The sagittal is decided by internal and external margin ofventral of above lateral mass of atlas and entrance point of screw, transversehorizontal line intersecting the midpoint, the intersection of the entrance point.Pedicle screw placement in atlas takes horizontal angle from6°to16°, verticalangle from3°to5°.Select a diameter of3.5mm, a length from21.7mm to30.5mm screw safety, objective and reliable.