螺旋CT扫描下测量颈椎椎弓根尺寸及螺钉置入角度

Transpedicular screw size and entrance angle measured by axial computed tomography

背景:在所有固定颈椎的技术上,椎弓根螺钉内固定可提供最大稳定性,但如进钉角度不正确易伤及颈髓、神经根和椎动脉。目的:测量下颈椎椎弓根尺寸和螺钉置入角度。设计、时间及地点:以正常人颈椎为对象的对比观察,于2004-12/2008-05在惠州市中心人民医院放射科完成。对象:选择惠州市中心人民医院骨科收治怀疑颈椎损伤患者60例,男30例,平均(42.9±18.9)岁;女30例,平均(42.2±14.9)岁。排除颈椎病理改变。CT下画经过椎弓根内外侧2条平行线与中线分别成50°和25°角,测量2条平行线间的垂直距离。方法:60例患者行颈椎CT扫描,扫描范围C2～T1,扫描电压140kV,电流200～250mA。主要观察指标:测量C3～C7椎弓根外径、内径和内壁皮质骨厚度,椎弓根轴长度、椎弓根进钉点到中线的垂直距离、椎弓根长轴与中线的夹角及椎弓根螺钉的有效距离。结果:颈椎椎弓根平均内径为1.3～3.3mm,平均外径为4.0～7.0mm,最小的椎弓根宽度在女性C3椎体,最小的椎弓根外径为3.2mm,最大椎弓根宽为C7,男性为11.1mm,女性为6.6mm。平均内壁皮质骨厚度为1.5～1.9mm,平均椎弓根轴长度29.3～33.7mm,平均椎弓根长轴与中线的夹角40.6°～49.6°,颈椎弓根钉进钉点到中线的垂直距离平均为20.2～23.7mm。椎弓根螺钉的有效距离(与中线成50°角)平均值3.8～6.6mm,最小值2.2mm,与中线成25°角的平均值2.8～4.4mm,最小值1.4mm。结论:颈椎椎弓根螺钉的置入应行CT测量,螺钉角度接近50°,进钉时保持向内的倾斜角度,防止损伤脊髓和椎动脉。

BACKGROUND： Of cervical fixation techniques, transpedicular screw internal fixation produces the largest stability. But incorrect screw entrance angle would damage cervical cord, nerve root or vertebral artery. OBJECTIVE： To measure the dimensions of the lower cervical pedicle and entrance points and insertion angles of transpedicular screws. DESIGN, TIME AND SETTING： Comparative observation with normal cervical vertebra. The experiment was performed at the Department of Radiology, Huizhou Municipal Central People＇s Hospital between December 2004 and May 2008. PARTICIPANTS： Sixty patients suspected to cervical injury were selected from Department of Orthopaedics, Huizhou Municipal Central People＇s Hospital, including 30 males aged （42.9±18.9） years, and 30 females aged （42.2±14.9）. Cervical pathological changes were excluded. Two parallel lines and one median were drawn on CT, with angle of 50° and 25° , to measure the vertical distance between two parallel lines. METHODS： CT scanning on cervical vertebra was performed in 60 patients with the range of C2T1 with voltage 140 kV, 200-250 mA. MAIN OUTCOME MEASURES： Pedicle inner and outer widths, medial cortical thickness, pedicle axis length, projected length of the pedicle axis and the pedicle transverse angle of C3- C7. RESULTS： The mean inner pedicle width ranged from 1.3 to 3.3 into and the mean outer pedicle width ranged from 4.0 to 7.0 ram. The smallest pedicle width was found at C3 among the females for both inner and outer pedicles; the smallest outer pedicle width was 3.2 mm; the largest pedicle width was at C7 in both males （ 11.1 mm） and females （6.6 mm）. The mean medial cortical thickness ranged from 1.5 to 1.9 mm. The pedicle axis length ranged from 29.3 to 33.7 mm. The mean pedicle transverse angle ranged from 40.6° to 49.6° .The mean vertical distance from the entrance point to median was 20.2 23.7 ram. The mean effective distance of the screw （50° with median） was 3.8-6.6 mm, and the minimum value was 2.2 ram, and the distance of the screw （25°with median） was 2.8-4.4 mm, and the minimum value was 1.4 ram. CONCLUSION： Axial CT measurements should facilitate transpedicular screw fixation in the lower cervical spine. The screw insertion angle should be close to 50 degrees, which is the mean pedicle transverse angle from C3- C6 to prevent spinal or vertebral artery injury.