Radial Tuberosity: Anatomy, Attachments, Relations, Function, Imaging

Topic

Radial tuberosity

The radial tuberosity is a rough, oval bony prominence located on the medial surface of the radius, just distal to its neck. It serves as the primary insertion site of the biceps brachii tendon, forming a critical attachment point for forearm flexion and supination.

This structure has a posterior rough portion and an anterior smooth portion; the rough posterior area provides insertion for the biceps tendon, while the anterior smooth area accommodates the bicipitoradial bursa, allowing frictionless movement between the tendon and bone during forearm rotation. The tuberosity plays an essential role in the biomechanics of the elbow and proximal forearm.

Synonyms

Bicipital tuberosity of radius
Tuberosity of radius

Location and Structure

Situated on the medial aspect of the proximal radius, just below the neck.
Shape: Oval, elongated in the anteroposterior direction.
Surface features:
- Posterior rough portion: For insertion of the biceps brachii tendon.
- Anterior smooth portion: Covered by the bicipitoradial bursa.
Orientation: Faces medially and slightly posteriorly when the forearm is in the anatomical position.
Lies opposite the ulnar tuberosity across the interosseous space, forming an important landmark for radioulnar articulation.

Relations

Anteriorly: Bicipitoradial bursa and biceps tendon sheath.
Posteriorly: Proximal radius shaft and adjacent supinator fibers.
Medially: Proximal ulna and interosseous membrane origin.
Laterally: Radial neck and supinator muscle fibers.
Superiorly: Neck of radius and lower border of radial head.
Inferiorly: Shaft of radius.

Attachments

Biceps brachii tendon: Inserts into the posterior rough area of the tuberosity.
Bicipitoradial bursa: Lies between the anterior smooth surface and the tendon, reducing friction.
Fascial extensions: A small expansion of the biceps tendon continues as the bicipital aponeurosis (lacertus fibrosus), contributing to forearm fascia.
Muscle proximity: Deep fibers of the supinator muscle arise just below the tuberosity.

Function

Primary attachment site: Serves as the strong insertion point for the biceps brachii tendon.
Forearm mechanics: Enables flexion at the elbow and supination of the forearm through the action of the biceps brachii.
Force transmission: Transfers muscular force from the upper arm to the radius, assisting in lifting and rotational movements.
Dynamic interaction: The bicipitoradial bursa allows smooth tendon movement during rotation, preventing frictional wear.

Clinical Significance

Biceps tendon rupture: Often occurs near or at the radial tuberosity; MRI helps evaluate tendon retraction and integrity.
Bicipitoradial bursitis: Inflammation of the bursa anterior to the tuberosity causes pain during supination.
Fractures: Avulsion or proximal radius fractures may involve the tuberosity and impair forearm flexion strength.
Surgical relevance: Important landmark in biceps tendon repair, supinator release, and radial head surgeries.
Imaging significance: MRI and CT evaluate insertional tears, bursitis, and osseous irregularities.

MRI Appearance

T1-weighted images:
- Cortical bone: Low signal (dark).
- Marrow: Bright signal due to fatty content.
- Biceps tendon: Low signal inserting on posterior rough area.
- Bicipitoradial bursa: Normally a thin low-signal line; distended with fluid in bursitis (intermediate-to-bright).
- Post-traumatic or degenerative changes: Irregular cortical margins or intermediate-signal marrow edema.
T2-weighted images:
- Cortex: Low signal (black).
- Marrow: Bright signal, slightly less than on T1.
- Biceps tendon: Low signal; partial tear appears as bright linear hyperintensity at insertion.
- Bicipitoradial bursa: Bright hyperintense fluid collection anterior to the tuberosity in bursitis.
- Fracture or edema: High signal intensity within subcortical bone.
STIR:
- Normal marrow: Intermediate-to-dark signal.
- Pathologic marrow: Bright hyperintensity indicating edema, contusion, or stress injury.
- Inflamed bursa: Bright hyperintense ovoid signal anterior to the tuberosity.
Proton Density Fat-Saturated (PD FS):
- Normal bone and tendon: Intermediate-to-dark signal.
- Abnormal: Bright signal along tendon insertion or within adjacent soft tissue.
- Excellent for detecting partial tendon tears, bursitis, and subtle periosteal edema.
T1 Fat-Sat Post-Contrast:
- Normal: Mild uniform enhancement of bone marrow.
- Inflamed bursa: Enhancing thin rim or surrounding fat plane enhancement.
- Post-surgical or reparative changes: Enhancement around tendon repair or scar tissue.

CT Appearance

Non-Contrast CT:

Cortex: High-density, well-defined bony prominence on medial aspect of proximal radius.
Marrow: Homogeneous low attenuation relative to cortex.
Bicipitoradial bursa: Not directly visible unless enlarged; appears as a low-attenuation soft-tissue density anterior to the tuberosity.
Fractures or avulsion: Clearly seen as cortical discontinuity or bone fragment separation.
Chronic changes: Hypertrophic bone or irregularities from chronic traction stress.

Post-Contrast CT (standard):

Enhancement: Highlights surrounding inflamed soft tissue and bursal thickening.
Utility: Evaluates post-traumatic inflammation, calcifications, and osseous detail in bicipitoradial bursitis or repair cases.

CT VRT 3D image

MRI image

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