APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -Nutation refers to anterior-inferior movement of the sacrum while the coccyx moves posteriorly relative to the ilium. Counternutation refers to a posterior-superior movement of the sacrum while the coccyx moves anterior relative to the ilium.

Detailed explanation-2: -Anterior nutation (sacral flexion) is a nodding movement of the sacrum between the innominates, with the sacral base moving anteriorly and inferiorly and the sacral apex moving posteriorly and superiorly.

Detailed explanation-3: -Think of the sacrum as a rudder that directs the movement of the abdominal cavity within the pelvis forward (anteriorly) and backward (posteriorly). On inhalation, we see counter-nutation of the sacrum in which the sacrum tilts backwards to increase the opening and available space within the pelvic inlet.

Detailed explanation-4: -Some of the muscles responsible for nutation include erector spinae and adductor magnus and some of the counter-nutating muscles include pectineus, adductor longus and brevis and latissimus dorsi.