In a superior vertical shear, which bone moves superior?

In a superior vertical shear, which bone moves superior?

• A. Occiput
• B. Sphenoid
• C. Both bones
• D. Neither bone moves

Answer: (A)

Vertical strains at the sphenobasilar junction involve the two bones moving in opposite directions along the vertical axis. In a superior vertical shear, the occiput rises relative to the sphenoid (the two bones separate with the occiput moving upward and the sphenoid effectively moving downward in relation). Because the upward movement is carried by the occiput, this pattern is described as the occiput moving superior. If the sphenoid were the bone moving upward, that would correspond to a different vertical strain pattern. And if neither bone moved or both moved together, you wouldn’t have a vertical shear.

Vertical strains at the sphenobasilar junction involve the two bones moving in opposite directions along the vertical axis. In a superior vertical shear, the occiput rises relative to the sphenoid (the two bones separate with the occiput moving upward and the sphenoid effectively moving downward in relation). Because the upward movement is carried by the occiput, this pattern is described as the occiput moving superior. If the sphenoid were the bone moving upward, that would correspond to a different vertical strain pattern. And if neither bone moved or both moved together, you wouldn’t have a vertical shear.