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Body of ulna

The body of the ulna, also known as the shaft of the ulna, is the long, central portion of the ulna extending between its proximal and distal ends. It forms a major structural component of the forearm and serves as an attachment site for multiple muscles and interosseous membrane, contributing significantly to forearm stability and function.

It is an important anatomical landmark in orthopedic anatomy, trauma assessment, and cross-sectional imaging of the forearm.

Synonyms

  • Shaft of the ulna

  • Diaphysis of the ulna

Location

  • Situated in the medial aspect of the forearm

  • Extends from the olecranon proximally to the ulnar head distally

  • Parallel to the radius along the forearm

  • Forms the medial border of the forearm

  • Subcutaneous along most of its posterior border

Anatomical components

  • Triangular shaft in cross-section

  • Three borders:

    • Anterior border

    • Posterior border (subcutaneous)

    • Interosseous border (lateral)

  • Three surfaces:

    • Anterior surface

    • Posterior surface

    • Medial surface

  • Interosseous border:

    • Gives attachment to the interosseous membrane

  • Muscle attachment sites:

    • Flexor digitorum profundus

    • Flexor carpi ulnaris

    • Extensor carpi ulnaris

    • Abductor pollicis longus

Relations

Anteriorly:

  • Flexor muscles of the forearm

  • Anterior interosseous vessels and nerve (deep relation)

Posteriorly:

  • Extensor muscles of the forearm

  • Subcutaneous surface (palpable along its length)

Laterally:

  • Interosseous membrane

  • Radius

Medially:

  • Subcutaneous tissue and skin

Proximally:

  • Olecranon and coronoid process

Distally:

  • Head of the ulna and ulnar styloid process

X-ray appearance

Plain radiographs (AP and lateral forearm views):

  • Ulna body: Straight, elongated radiopaque structure

  • Cortical margins: Smooth and continuous

  • Medullary cavity: Central radiolucent canal

  • Alignment: Parallel to the radius

  • Best seen on: AP and lateral projections

CT appearance

Non-contrast CT:

  • Cortical bone: High-density outer shell

  • Trabecular bone: Lower-density medullary cavity

  • Shape: Triangular cross-section well appreciated

  • Interosseous border: Clearly defined

  • Spatial detail: Excellent for assessing contour and cortical integrity

MRI appearance

T1-weighted images:

  • Cortex: Low signal intensity

  • Marrow: High signal intensity (fatty marrow in adults)

  • Muscle interfaces: Well delineated

T2-weighted images:

  • Cortex: Low signal

  • Marrow: Intermediate signal

  • Surrounding muscles: Intermediate-to-high signal

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Bone outline: Clearly visualized

  • Soft tissues: High contrast with suppressed marrow

Proton density fat-saturated (PD FS):

  • Marrow: Suppressed fat signal

  • Cortex: Low signal

  • Muscle attachments and interosseous membrane: Well visualized

MRI image

Body of ulna mri anatomy labelled image-img-00000-00000

X-Ray image

Body of ulna x ray anatomy labelled image-img-00000-00000