Anatomy Of The Deltoid Muscle - Everything You Need To Know - Dr. Nabil Ebraheim

Dr. Ebraheim’s educational animated video describes the anatomy of the Deltoid muscle.
The deltoid muscle begins at the lateral third of the clavicle, acromion and spine of the scapula continuing down to its insertion into the deltoid tuberosity of the humerus.
The shoulder and deltoid muscle gets its rounded appearance due to the deltoid passing over the proper part of the humerus.
The middle part of the deltoid is responsible for abduction of the arm, which raises the arm to the horizontal level.
The anterior part of the deltoid muscle flexes and medially rotates the arm.
The posterior part of the deltoid muscle extends and laterally rotates the arm.
The axillary nerve supplies the deltoid muscle, giving sensation over the shoulder area, the axillary nerve originates from the posterior cord of the brachial plexus.
When the nerve is injured:
- Weakness of the shoulder abduction.
- Atrophy of the deltoid.
- Numbness of the deltoid region.
The axillary nerve is commonly injured due to fractures of the shoulder joint.
The deltoid branch of the thoracoacromial artery arises from the axillary artery and supplies the deltoid muscle anteriorly.
The deltoid muscle also gets arterial supply in the posterior aspect from the posterior humeral circumflex artery.
The quadrangular space is the space that the posterior circumflex humeral artery and axillary nerve pass through on the way to the deltoid muscle.
A rupture in the deltoid muscle can occur from sports or heavy manual labor, complete rupture is not common.
Rupture of the deltoid usually occurs from open shoulder surgery.
Open procedure of the shoulder may compromise the deltoid attachment to the clavicle and acromion.
Be aware of Os Acromiale and attachment of the deltoid as surgery of the Os Acromiale may weaken the deltoid muscle.
Total acromionectomy is a bad procedure, it compromises the deltoid function.
Arthroscopic procedure is better than open shoulder procedure, rupture of the deltoid needs to be repaired or reconstructed.
Danger of the Lateral Approach:
- Incision from the tip of acromion extended distally.
- The incision and deltoid is split and the incision should not be more than 5 cm distal to the acromion to protect the axillary nerve.
- The axillary nerve runs transversely from posterior to anterior about 7 cm distal to the acromion.
- If the incision needs to be extended distally, as in fixation of the proximal humerus, an anterolateral incision over the humeral shaft may be used.


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