Deltoid muscle

Paralysis of the Deltoid Muscle: Axillary Nerve Palsy


Weakness of the shoulder particularly in lifting the arm. When standing, arm can move out from the side, but not past about 45 to 60 degrees: and not above the shoulder. Other muscles and nerves can be injured at the same time as the injury that paralyses this muscle: that may change the advice for repair.

Wasting of the muscle will occur: the roundness of the shoulder will disappear, and the bones of the shoulder become more prominent as time passes after the injury.

Numbness in the ‘shoulder badge’ area usually occurs.


As a solitary injury this nerve is most commonly damaged by difficult dislocation of the shoulder . It can be damaged at the time of shoulder replacement surgery, and in high energy injuries around the shoulder, and base of neck.

 Deltoid Muscle Before Surgery

Before Surgery:

Upper Pectoralis Major Outlined

Delto-Pectoral Groove solid line


Assessment and treatment of this injury depends on the cause. It is commonly advised to wait for nerve recovery for up to 6 months after shoulder dislocation. Some partial recovery should be found before that time: either with some sensation returning, or with twitches returning to the muscle. Expert assessment should be considered if the muscle is completely paralysed at 3 months after injury: because should nerve repair be needed, there is a time window for regrowth and it is imperative to avoid delay.

While waiting keep your shoulder flexible: this is a joint that will stiffen easily: and a weak muscle won’t move a stiff joint so get advice and supervision on exercises.

Between 3 and 6 months clinical review with experienced clinical testing of the muscle function and sensation is essential. An electromyography study may be needed to help decide whether surgery to explore the injury is needed. Most xray and MRI studies are not entirely helpful as their inaccuracy can confuse the issues.


The nerve damage needs to be inspected from an incision at the front of the shoulder, as well as from behind the shoulder. If the nerve was completely torn, the remnants can be found, and trimmed but will need cables of another nerve to bridge the gap between the ends. Usually the other nerve is taken from a long nerve in the outer part of the leg, leaving a numb patch on the outer aspect of the heel (sural nerve graft).

In some injuries, where the nerve is too badly damaged, or where the delay to repair has been long (more than 12 months since injury) the repair may be tried using fibres that usually control part of the triceps muscle. There are some pros and cons for that decision that your surgeon shall discuss with you.

After the nerve repair, we wait. During that time it remains important to keep joint flexibility, and as much arm activity as possible. Recent studies have developed techniques that help the brain to stay ready for nerve regrowth and recovery.

When the muscle starts to produce weak twitches, then the nature of therapy can change: exercises to gradually increase strength and control are introduced. Most people will develop satisfactory recovery depending on their individual factors of health, injury, repair and exercise routines.

Chronic Paralysis of the Deltoid:

A muscle transfer may be helpful to some people who have long-term paralysis of the deltoid muscle. This clinic has successfully improved shoulder function for several people with that paralysis, who do have strong normal function of the pectoralis major muscle on that side. The operation is quite major, does leave a lengthy scar from deltoid, across the collar bone and down the sternal edge, but has been successful in allowing much better shoulder control and arm abduction.

Significant function has been recovered after 6 weeks from the surgery.

- Philip A. Griffin, FRACS

 Deltoid Muscle typical scarTypical scar after surgery
 Deltoid Muscle Unassisted Sholder AbductionUnassisted Shoulder Abduction
at 10 weeks after surgery