What motion unit is affected by a sacral base posterior?

What motion unit is affected by a sacral base posterior?

• A. Atlanto-occipital joint
• B. Lumbosacral junction
• C. Sacroiliac joint
• D. Cervicothoracic junction

Answer: (B)

A sacral base posterior is a movement of the sacrum that changes how it interacts with the lumbar spine. The key point is the lumbosacral junction—the articulation between L5 and the sacrum. When the sacral base moves posteriorly, the motion is transmitted at this boundary, making the lumbosacral junction the primary site affected. The other regions—the neck joints and the cervicothoracic junction—are not directly involved in this sacral–lumbar relationship, and while the sacroiliac joints can follow sacral motion, the main motion unit altered by a posterior sacral base is the lumbosacral junction.

A sacral base posterior is a movement of the sacrum that changes how it interacts with the lumbar spine. The key point is the lumbosacral junction—the articulation between L5 and the sacrum. When the sacral base moves posteriorly, the motion is transmitted at this boundary, making the lumbosacral junction the primary site affected. The other regions—the neck joints and the cervicothoracic junction—are not directly involved in this sacral–lumbar relationship, and while the sacroiliac joints can follow sacral motion, the main motion unit altered by a posterior sacral base is the lumbosacral junction.