abduktio

Abduktio, or abduction, is a term used in anatomy to describe movement that directs a body part away from the midline of the body or from a reference axis. The word originates from the Latin abductio, from abducere meaning “to lead away.” In English, the term abduction is most common, while abduktio appears in Latinized or non-English medical texts.

In the limbs, abduction refers to moving a limb laterally away from the midline. Examples include shoulder abduction, which lifts the arm away from the body, and hip abduction, which moves the leg outward. Range of motion varies by joint and individual; shoulder abduction can approach about 180 degrees with accompanying scapular movement, while hip abduction is typically around 40–50 degrees. Abduction also describes movements of the fingers and toes away from the axis of the hand or foot, performed by specific intrinsic muscles.

In the eye, abduction is the outward movement of the eyeball away from the midline, accomplished by the lateral rectus muscle and innervated by the abducens nerve (cranial nerve VI).

Muscles that produce abduction are called abductors. Notable examples include the deltoid and supraspinatus for the shoulder, the gluteus medius and minimus for the hip, and the abductor digiti minimi for the little finger. Abduction is contrasted with adduction, which moves a part toward the midline, and with other directional terms such as flexion, extension, and rotation.

See also: adduction, abductor, abducens nerve, ocular movement.