Deltoid muscle

Deltoid muscle is a large triangular muscle covering the shoulder joint.

The deltoid muscle

Anatomy

• The deltoid muscle arises from the anterior border and upper surface of the lateral third of the clavicle
• The deltoid is inserted into the deltoid prominence on the middle of the lateral side of the body of the humerus.
• At its insertion the muscle gives off an expansion to the deep fascia of the arm.
• The deltoid muscle is remarkably coarse in texture
• Variations—Large variations uncommon.

Deltoid muscle

Function

The deltoid muscle helps abduct, flex, extend and rotate the arm.

Deltoid

Blood supply

The deltoid is supplied by the following three arteries:

• thoracoacromial artery (acromial and deltoid branches)
• the circumflex humeral arteries, and
• the profunda brachii artery (deltoid branch).

Nerve supply

The deltoid muscle is innervated by the axillary nerve

Common problems associated with deltoid muscle

The most common abnormalities affecting the deltoid muscle are tears, fatty atrophy, and enthesopathy.

IM injections

Most intramuscular injections in the upper arm are given in to the deltoid muscle in an inverted triangular area in the upper portion of the arm.

1. Find the bony prominence at the top of the arm called acromion process.
2. The top border of an inverted triangle is two finger widths down from the acromion process.
3. Stretch the skin and then hold or fell the muscle.
4. Insert the needle at a right angle(90 degrees) to the skin in the center of the inverted triangle

Etiology of name

The name deltoid refers to the shape of the Greek letter Delta

Other names

Deltoideus