Anatomical Study Of Bone Landmark Of Atlas Pedicle And Clinical Application

Objective: To set up a safe axes of atlas pedicle(M line) when atlas pedicle is inserted a screw and to find out anatomical landmark of atlas pedicle when atlantoaxis existed rotatory dislocation or obvious separation from each other. Methods: 100 dried atlas were measured to get the parameters both the axes of atlas and anatomic landmark from its superior, left and right. The vertebral artery groove and the atlas lateral mass were measured to get some related data. The result of the measurement was checked by experiment of dried specimen and cadaveric specimen. We applied the method of our study to suitable patients in preliminary clinical practice after the experiment. Results: Pedicle axes of atlas relative to sagittal plan was 17°. The entrance point of atlas pedicle screw was 25mm to the posterior median point of the posterior arch. Posterior tubercle of the posterior arch could be as a landmark. The entrance point of atlas pedicle screw was 22mm to the lateral edge of transverse process. The posterior convexity of superior articular surface of atlas was protrusion and a bulge of bone cortex under the convexity was protrusion. The peak of the bulge accorded with the vertical line through the posterior convexity of superior articular surface of atlas. The superimpose rate of the vertical line with the M line were 48% to left and 65% to right. The surplus existed in l～2mm to lateral of M line. The exit point of screw was the median point of vertical line on the anterior cortex of lateral mass. The superimpose rate of BB line (the line linked with the...