Ma Xiang-Yang, Yin Qing-Shui, Wu Zeng-Hui, Xia Hong, Riew K Daniel, Liu Jing-Fa
From the *Department of Orthopedics, Guangzhou Liu Hua Qiao Hospital, Guangzhou, People's Republic of China; and †Department of Orthopedics, Washington University School of Medicine, St. Louis, MO.
Spine (Phila Pa 1976). 2010 Mar 15;35(6):704-8. doi: 10.1097/BRS.0b013e3181bb8831.
A cadaveric specimen study.
To determine the applicability of a modified C2 translaminar screw placement in the general adult population and to provide pertinent clinical data for screw insertion.
C2 intralaminar screw fixation has recently been popularized, but this technique carries a potential drawback that the screw may breakout ventrally into the spinal canal. For this reason, a modified C2 translaminar screw fixation technique was developed to intraoperatively verify screw position and thereby decrease the risk or canal compromise. To our knowledge, there has been not an anatomic study evaluating this modification of the translaminar screw technique.
The tips of the modified screws were aimed such that they exited the dorsal cortex of the center of the contralateral lateral mass, achieving bicortical fixation. A total of 120 adult C2 vertebrae were evaluated bilaterally for the following: thickness of the cranial, midportion, and caudal edge of C2 lamina; the heights of the spinous process, lamina, and lateral mass; inclination angle of the laminae, screw projection length, and trajectory angle of cranial and caudal C2 translaminar screw.
A total of 83.3% specimens had bilateral laminar thicknesses ≥4.0 mm and a spinous process height ≥9.0 mm; 5% had a laminar thickness less than 4.0-mm bilaterally; 9.2% had a laminar thickness less than 4.0 mm on one side; 2.5% had a spinous process height lower than 9.0 mm.
A large percentages of C2 laminae are of sufficient size to safely accommodate a bicortical 3.5-mm diameter screw. The thickness of the lamina and the height of the spinous process are the 2 limiting factors for safe translaminar screws placement. Using a bicortical technique confirms the position of the screw and thereby helps to decrease the risk of neurologic injury from screw penetration of the inner cortex of the lamina.
尸体标本研究。
确定改良C2经椎板螺钉置入术在一般成年人群中的适用性，并为螺钉置入提供相关临床数据。
C2椎板内螺钉固定术近来已得到推广，但该技术存在一个潜在缺点，即螺钉可能向腹侧穿破进入椎管。因此，开发了一种改良的C2经椎板螺钉固定技术，以便在术中验证螺钉位置，从而降低椎管受损风险。据我们所知，尚未有解剖学研究评估这种经椎板螺钉技术的改良。
改良螺钉的尖端指向对侧侧块中心的背侧皮质穿出，实现双侧皮质固定。对120个成人C2椎体双侧进行以下评估：C2椎板颅侧、中部和尾侧边缘的厚度；棘突、椎板和侧块的高度；椎板倾斜角度、螺钉突出长度以及C2颅侧和尾侧经椎板螺钉的轨迹角度。
总共83.3%的标本双侧椎板厚度≥4.0 mm且棘突高度≥9.0 mm；5%的标本双侧椎板厚度小于4.0 mm；9.2%的标本一侧椎板厚度小于4.0 mm；2.5%的标本棘突高度低于9.0 mm。
很大比例的C2椎板尺寸足够大，能够安全容纳直径3.5 mm的双侧皮质螺钉。椎板厚度和棘突高度是安全经椎板螺钉置入的两个限制因素。采用双侧皮质技术可确认螺钉位置，从而有助于降低因螺钉穿透椎板内皮质而导致神经损伤的风险。
