螺旋CT扫描下颈椎为下颈椎椎弓根螺钉的置入提供依据

Transpedicular screw placement evaluated by axial computed tomography of the lower cervical pedicle

目的通过测量颈椎椎弓根尺寸和进钉点进钉角度,为置入椎钉提供依据。方法选择2004年12月至2005年10月我院和惠州市中心人民医院骨科收治的怀疑颈椎损伤患者60例,其中男30例,平均年龄(43±19)岁,女30例,平均年龄(42±15)岁。均排除颈椎病理改变。60例患者行颈椎CT扫描,扫描范围第2颈椎～第1胸椎,扫描电压140 kV,200～250 mA。结果颈椎椎弓根平均内径为1.3～3.3 mm,颈椎椎弓根平均外径为4.0～7.0 mm,最小的椎弓根宽度在女性第3颈椎椎体,最小的椎弓根外径为3.2 mm,最大椎弓根宽是第7颈椎,男性为11.1 mm,女性为6.6 mm。平均内壁皮质骨厚度为1.5～1.9 mm,平均椎弓根轴长度29.3～33.7 mm,平均椎弓根长轴与中线的夹角40.6°～49.6°,颈椎椎弓根钉进钉点到中线的垂直距离平均为20.2～23.7 mm。结论颈椎椎弓根螺钉的置入应行CT测量,螺钉角度接近50°,进钉角度尽可能偏外侧。

Objective To provide a safe transpedieular serew trajectory by measuring the dimensions of the lower cervical pedicle and evaluating the entrance points and the insertion angles of transpedieular screws. Methods The dimensions of the pedieles （ C3 - C7 ） were determined in 60 patients with cervieal spinal lesions from CT images. Change of pathology of cervical vertebra was excluded. CT scanning on cervical vertebra was performed in 60 patients with the range of C2 - T1, electric pressure was 140 kV, 200 - 250 mA, and depth of cross section was 3 mm. CT images in which each pediele appeared largest were selected and the following dimensions determined：pediele inner and outer widths, medial cortical thickness, pediele axis length, projeeted length of the pedicle axis and the pedicle transverse angle. Results The mean inner pedicle width ranged from 1.3 to 3.3 mm, the mean outer pediel width ranged from 4.0 to 7.0 mm. The smallest pedicle width was found at C3 among the female subjects for both inner and outer pedieles, The smallest outer pediele width was 3.2 mm, the largtest pediele width was at C7 in both males （11.1 mm）and females （7.4mm）. The mean medial cortical thickness range from 1.5 to 2.0 mm. The pediele axis length ranged from 29.3 to 33.7 mm. The mean pediele transverse angle ranged from 40.6° to 49.6°. Conclusion Axial CT measurements should facilitate transpedicular screw fixation in the lower cervical spine. We believe that the screw insertion angle should be close to 50 degrees, which is the mean pediele transverse angle from C3 - C6. The entry point of the pediele screw should be located as laterally as possible in the posterior surface of the lateral mass.