MOD 6 - Rotation, Obliquity, Inversion & Eversion

Twenty-four question-and-answer flashcards covering rotation, obliquity, inversion, eversion, lateral ankle evaluation, and clinical adaptation for lower-limb radiographic positioning.

What is the key difference between rotation and obliquity?

Rotation is circular movement around a body part’s long axis, whereas obliquity is the angled position of the part relative to a true AP or PA projection.

How is an oblique body position defined?

When the long axis of the body is neither supine, prone, nor lateral—i.e., the body is angled (oblique) to the IR.

How is a right anterior oblique (RAO) position described?

The patient is rotated so the right anterior surface is in contact with the image receptor.

How is obliquity of an extremity described?

By the direction of rotation (medial/internal or lateral/external) and which side of the limb is closest to the IR.

What details should be included when describing optimal rotation?

State the degree of rotation and the reference starting point, e.g., “30° anterior from the coronal plane.”

How should suboptimal rotation be corrected?

Indicate whether rotation must be increased or decreased and specify the direction of adjustment.

What does the term “medial oblique foot” describe?

The medial (inner) side of the foot is closest to the IR with the foot internally (medially) rotated.

Name two ways to achieve a 15° mortise ankle view when a patient can only rotate 10°.

1) Place a sponge under the pelvis/leg to add body rotation; 2) Angle the central ray 5° lateromedially.

Why angle the CR lateromedially for the mortise ankle?

To clear the tibia and open the ankle joint because the fibula sits posteriorly.

Why can’t you angle the CR when using a DR bucky?

Angling the CR into a grid can create grid cut-off and degrade the image.

What is inversion of the foot?

Inward movement toward midline so the plantar surface turns medially.

What is eversion of the foot?

Outward movement away from midline so the plantar surface turns laterally.

What is a memory tip for inversion?

Inversion = Inward movement.

How do inversion and eversion relate to AP foot rotation?

Inversion corresponds to lateral/external rotation; eversion corresponds to medial/internal rotation.

How do you correct an inverted AP foot image?

Evert the foot until the plantar surface becomes parallel with the IR.

Why is adjusting to plantar-surface parallel better than equal weight distribution for correcting an inverted AP foot?

Parallel alignment is easier to confirm radiographically than evaluating equal weight bearing.

Radiographically, what does inversion look like on a lateral ankle?

Medial talar dome appears proximal, lateral dome distal; cuboid is more free; talocalcaneal joint opens.

Radiographically, what does eversion look like on a lateral ankle?

Medial talar dome appears distal, lateral dome proximal; cuboid becomes more superimposed; talocalcaneal joint closes.

How do the malleoli appear during inversion?

The lateral malleolus appears more distal than the medial malleolus.

How do the malleoli appear during eversion?

The lateral malleolus appears closer to or even proximal to the medial malleolus.

What is the goal when assessing rotation and inversion/eversion together in a lateral projection?

To obtain open ankle joints and superimposed talar domes in both directions for a true lateral image.

What is a quick method for evaluating a lateral foot or ankle image?

First identify medial versus lateral talar domes, then assess rotation followed by inversion/eversion.

What factors guide decisions to repeat rotated or I/E-affected images?

Best practice standards, patient history, clinical information, and overall exam context.

How can patient anatomy affect the degree of rotation needed?

Anatomic variations such as foot arch height may require more or less rotation or CR angulation to achieve optimal positioning.