The middle (acromial) head of the deltoid is the largest and most powerful of the three deltoid heads, forming the rounded shoulder contour. Its multipennate architecture allows it to generate considerable force for arm abduction from 15 to 90 degrees, after which the supraspinatus contribution diminishes and the deltoid becomes the primary abductor. The middle head is the target of intramuscular injection in the deltoid.
| Origin | Lateral border and superior surface of the acromion |
|---|---|
| Insertion | Deltoid tuberosity of the humerus via the deltoid V |
| Nerve Supply | Axillary nerve (C5, C6) |
| Blood Supply | Posterior circumflex humeral artery; Deltoid branch of thoracoacromial artery |
| Actions |
|
|---|
It is the main abductor of the arm, lifting the arm out to the side from about 15 to 90 degrees.
Middle deltoid atrophy is the most visible sign of axillary nerve palsy, producing a flat shoulder profile and a positive drop arm test. Selective middle head wasting occurs in quadrilateral space syndrome and after proximal humeral fracture with axillary nerve traction. EMG of the middle deltoid is the most sensitive indicator of axillary nerve function. Intramuscular deltoid injections must target the middle head to avoid the axillary nerve inferiorly and the acromioclavicular joint superiorly.
Palpated with the arm held in 90 degrees abduction against resistance, where it forms a firm, rounded mass lateral to the acromion. The middle head is distinguished from the anterior and posterior heads by its direct lateral position.
Paralysis of the middle deltoid from axillary nerve injury in shoulder dislocation or proximal humeral fracture, producing a flat shoulder, absent abduction power, and a small patch of lateral arm numbness.
Partial tear of the acromial head from sudden forced adduction or eccentric overload, presenting as lateral shoulder pain and weakness with resisted abduction at 90 degrees.
This website uses cookies to enhance your experience. Some are essential for site functionality, while others help us analyze and improve your usage experience. Please review your options and make your choice.
If you are under 16 years old, please ensure that you have received consent from your parent or guardian for any non-essential cookies.
Your privacy is important to us. You can adjust your cookie settings at any time. For more information about how we use data, please read our privacy policy. You may change your preferences at any time by clicking on the settings button below.
Note that if you choose to disable some types of cookies, it may impact your experience of the site and the services we are able to offer.
Some required resources have been blocked, which can affect third-party services and may cause the site to not function properly.
This website uses cookies to enhance your browsing experience and ensure the site functions properly. By continuing to use this site, you acknowledge and accept our use of cookies.
