Anteroposterieure

Anteroposterieure, more commonly rendered as anteropostérieur or antéropostérieur in French, is a directional term used in anatomy to describe a line, axis, or projection that runs from the anterior (front) to the posterior (back) of the body or a structure. It is defined relative to the sagittal plane and is often contrasted with posteroanterior or anteroposterior directions depending on context.

In anatomical description, the term denotes the front-to-back axis of a structure. It is widely used in clinical imaging and anatomical labeling to specify orientation, relationships between parts, and the direction of a projection or slice.

In radiology, anteropostérieur (AP) describes a projection in which the X-ray beam passes from the anterior surface toward the posterior surface. The opposite orientation is posteroanterior (PA). The choice between AP and PA has practical implications: AP views are commonly used when a patient cannot stand or be positioned for a PA view, such as in pediatric, critically ill, or immobilized patients. AP projections can magnify central structures, especially the heart, compared with PA projections.

Beyond imaging, the anteroposterior axis is used in anatomy and biomechanics to describe measurements and orientations, such as the anteroposterior diameter of a chest or pelvis and to characterize alignment or deformities along the front-to-back direction.