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Deltoid tuberosity

The deltoid tuberosity is a rough, V-shaped bony prominence located on the lateral aspect of the humeral shaft. It serves as the insertion site of the deltoid muscle, which is the main abductor of the shoulder. The tuberosity marks the transition between the upper and middle thirds of the humerus and provides an important landmark for muscle attachment, surgical orientation, and imaging identification.

The deltoid tuberosity functions as a key anchor point for transmitting the force of shoulder abduction, and it is often visible or palpable in muscular individuals. It has both anterior and posterior lips corresponding to the muscle’s multipennate fiber arrangement, giving the bone its characteristic roughened surface.

Synonyms

  • Deltoid crest of humerus

  • Lateral humeral ridge

Location and Structure

  • Found on the lateral surface of the humeral shaft, approximately halfway between the humeral head and the lateral epicondyle.

  • Appears as a rough, raised V-shaped prominence, with its apex directed inferiorly.

  • The upper border blends with the attachment of the lateral head of the triceps posteriorly and the brachialis anteriorly.

  • The cortical bone here is thickened due to muscular traction forces.

Relations

  • Anteriorly: Brachialis muscle and branches of the anterior circumflex humeral vessels

  • Posteriorly: Lateral head of the triceps brachii

  • Laterally: Deltoid muscle insertion fibers

  • Medially: Shaft of humerus and radial groove (posteriorly located)

  • Superiorly: Deltoid muscle origin and shoulder joint region

  • Inferiorly: Continuation into smooth humeral shaft

Attachments

  • Deltoid muscle insertion: The deltoid attaches via strong tendinous fibers to the roughened surface, allowing powerful abduction of the arm.

  • Fascial extensions: Deep fascia of the arm anchors to the tuberosity margin.

  • Intermuscular septa: Serve as partitions between the deltoid, brachialis, and triceps brachii along the humerus.

Arterial Supply

  • Branches of the posterior circumflex humeral artery and profunda brachii artery, supplying periosteal and muscular regions around the tuberosity.

Function

  • Muscle insertion: Provides leverage and secure attachment for deltoid fibers.

  • Force transmission: Transfers abduction and elevation forces from the deltoid to the humeral shaft.

  • Structural reinforcement: The cortical thickening resists torsional stress from shoulder movement.

  • Clinical landmark: Used during orthopedic surgeries and imaging as a reference for humeral alignment.

Clinical Significance

  • Fractures: Commonly involved in spiral or transverse fractures of the humeral shaft. The deltoid pull may cause fragment displacement.

  • Traction injury: Excessive deltoid contraction or trauma can cause avulsion fractures at the tuberosity.

  • Osteomyelitis or periostitis: May cause cortical thickening or irregularity visible on imaging.

  • Surgical relevance: Important reference point for intramedullary nailing and shoulder arthroplasty.

  • Myositis ossificans: Can develop near the deltoid insertion following trauma.

  • Imaging role: Useful landmark for assessing humeral rotation, muscle atrophy, or fracture alignment on MRI/CT.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark), sharply defined.

    • Bone marrow: Bright, due to fatty marrow signal in adults.

    • Deltoid insertion: Intermediate-to-low signal intensity at tendon-bone interface.

    • Pathology: Avulsion or enthesopathy appears as irregular low-signal cortical disruption.

  • T2-weighted images:

    • Cortex: Dark, low signal.

    • Marrow: Bright, though slightly less intense than on T1.

    • Deltoid tendon insertion: Appears as low-signal linear band; partial tears or enthesitis show focal hyperintensity.

    • Surrounding soft tissues: Show bright signal in edema or hematoma after trauma.

  • STIR:

    • Normal cortex: Dark, low signal.

    • Normal marrow: Intermediate-to-dark signal.

    • Pathology: Bright hyperintensity in marrow or soft tissues in cases of edema, inflammation, or acute fracture.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow and cortex: Intermediate-to-dark signal.

    • Deltoid attachment: Homogeneous low signal, continuous with muscle belly.

    • Abnormal findings: Focal bright signal at tendon insertion in tendinitis or traction injury.

    • Excellent for detecting: Subtle cortical avulsions, bone contusions, and periostitis.

  • T1 Fat-Sat Post-Contrast:

    • Normal periosteum: Mild uniform enhancement.

    • Inflammation or enthesopathy: Focal or diffuse enhancement at the deltoid insertion.

    • Post-traumatic changes: Enhancement surrounding bone fragments or soft-tissue hematoma.

CT Appearance

Non-Contrast CT:

  • Cortex: High-density, clearly marginated along humeral shaft.

  • Deltoid tuberosity: Seen as a rough, elevated ridge on the lateral humerus.

  • Trabecular pattern: Coarse and dense near tendon insertion due to stress reinforcement.

  • Pathology:

    • Avulsion or traction fractures appear as cortical irregularities or small displaced fragments.

    • Chronic traction changes show cortical thickening or periosteal reaction.

Post-Contrast CT (standard):

  • Normal bone: Enhances minimally and uniformly.

  • Periostitis or inflammatory lesions: Focal enhancement of periosteum or adjacent soft tissue.

  • Useful for: Detecting occult fracture lines, enthesopathic changes, and assessing bone healing post-surgery.

MRI images

deltoid tuberosity axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI images

deltoid tuberosity sag cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000