ABSTRACT
<p><b>OBJECTIVE</b>To study the relationship between cervical pedicle and compressed spinal cord.</p><p><b>METHODS</b>One hundred and five patients (53 male,52 female,age from 29 to 80 years) with cervical spondylotic myelopathy who needed surgery were included from December 2011 to January 2013 in Shengjing Hospital. Plain MRI scan was used for cross section of C4 - C7 vertebral bodies parallel to the axis of bilateral pedicle, and the images were sent to the workstation. PACS system was applied to measure the anatomical parameters related to the security of cervical pedicle screw, including the shortest distance from medial left/right cervical pedicle to the cervical spinal cord (LH/RH), and the smallest angle between the longitudinal axis of left/right cervical pedicle and the screw which was assumed to just touch the cervical spinal cord (LSA/RSA). All these data in each segment were classified according to compression or not:with compression and without compression. Twelve cases were selected and measured by MRI and 3D cervical CT for spinal canal width D, namely the straight-line distance between the medial margins of cervical pedicle. And the results of two methods were compared to see whether there were statistical differences.</p><p><b>RESULTS</b>At C4, LH was (7.2±1.3) mm, RH was (6.7±1.4) mm, and the average was (6.9±1.4) mm; at C5, LH was (7.7±1.4) mm, RH was (6.7±1.4) mm, and the average was (7.2±1.5) mm; at C6, LH was (8.2±1.5) mm, RH was (6.9±1.3) mm, and the average was (7.5±1.5) mm; at C7, LH was (8.2±1.4) mm, RH was (7.3±2.1) mm, and the average was (7.7±1.8) mm. At C4, LSA was 34.4°±4.2°, RSA was 34.4°±5.2° and the average angle was 34.4°±4.7°; at C5, LSA was 35.9°±5.2°, RSA was 34.6°±5.4° and the average angle was 35.3°±5.3°; at C6, LSA was 37.4°±4.8°, RSA was 34.8°±4.8° and the average angle was 36.1°±5.0°; at C7, LSA was 39.2°±5.8°, RSA was 37.1°±5.2° and the average angle was 38.1°±5.6°; There were no statistically significant differences between segments with and without compression in H, SA and D (all P>0.05).</p><p><b>CONCLUSIONS</b>There is security space between the medial vertebral pedicle and compressed spinal cord. There is individual variation in security space. It is very necessary to identify security space before surgery by MRI, emphasize individual procedure and avoid spinal cord injury.</p>