Angle of ipsilateral outer lamina cortex to pedicle axis Virtual screw trajectory 2 mm from and parallel to the lamina was placed through the LM. Potential violation of the transverse foramen and LM width available for screw purchase was assessed
Females: Right: C3–84.8°(2.6), C4–85.2°(3.1), C5–86.7°(3.3), C6–89.2°(2.5), C7–92.3°(2.4); Left: C3–84.0°(3.1), C4–84.5°(3.9), C5–86.6°(3.7), C6–89.6°(2.6), C7–92.1°(2.3) No significant difference between males and females (P<
0.05) Violation of transverse foramen C3–C7: 0% LM width (trajectory parallel to LM) in millimetres (standard deviation): Males: Right: C3–5.5(0.7), C4–6.1(0.7), C5–6.8(0.8), C6–7.1(1.1), C7–6.1(1); Left: C3–5.2(0.8), C4–5.9(0.8), C5–7(1.2), C6–7.3(1.1), C7–6.3(1.4) Females: Right: C3–5.3(0.8), C4–5.5(0.9), C5–6.6(1.2), C6–6.3(1.3), C7–5.4(1.4); Left: C3–5.2(1), C4–5.7(1), C5–7.1(1.1), C6–6.5(1.3), C7–5.5(1.6)
LM screws placed parallel to the lamina find sufficient LM width and are highly unlikely to injure the vertebral artery in bi-cortical placement. This technique appears favourable over conventional 30° LM placement.
