Which axis is involved with compression of the SBS?

• A. Left-right axis
• B. Anteroposterior axis
• C. Vertical axis
• D. Superior-inferior axis

Answer: (B)

Compression at the SBS occurs along the anteroposterior axis because the front-to-back line is the direction in which the sphenoid and occiput move toward each other. In cranial mechanics, the SASB/occiput relationship is most prominently described as compressing or opening along the AP plane, so a restriction here manifests as compression along that front-to-back axis. The other axes describe motions that are more about side-to-side (left-right) torsion and up-down (superior-inferior) movements, which are not the primary direction of SBS compression. Focusing on the AP axis helps explain why releasing the SBS compression involves allowing a glide or separation along the front-to-back direction between the sphenoid and occiput.