How do the sphenoid and occiput move in vertical strains of the SBS?

How do the sphenoid and occiput move in vertical strains of the SBS?

• A. Rotation in the same direction around two horizontal axes
• B. Rotation in opposite directions around two vertical axes
• C. Rotation around the anteroposterior axis only
• D. No rotation occurs

Answer: (A)

Vertical strains challenge you to see the sphenoid and occiput moving as a pair along the vertical axis. In this pattern, the sphenoid and occiput rotate in the same direction around two horizontal (transverse) axes. That synchronized, same-sense rotation changes the height relationship between the sphenoid base and occipital base, producing a vertical displacement of the SBS as a unit. The other motion patterns don’t create that vertical displacement: rotating around vertical axes in opposite directions describes torsion, rotating around the AP axis alone is a single-axis rotation pattern, and no rotation would mean no strain at all.

Vertical strains challenge you to see the sphenoid and occiput moving as a pair along the vertical axis. In this pattern, the sphenoid and occiput rotate in the same direction around two horizontal (transverse) axes. That synchronized, same-sense rotation changes the height relationship between the sphenoid base and occipital base, producing a vertical displacement of the SBS as a unit.

The other motion patterns don’t create that vertical displacement: rotating around vertical axes in opposite directions describes torsion, rotating around the AP axis alone is a single-axis rotation pattern, and no rotation would mean no strain at all.