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The deltoid muscle is a large shoulder muscle and its principal abductor. The axillary nerve, which originates from the brachial plexus, is the main nerve that supplies the deltoid muscle. The axillary nerve travels through the quadrangular space and divides into anterior and posterior branches to supply the deltoid muscle and the skin over the deltoid. The axillary nerve can be damaged through trauma to the proximal humerus or shoulder girdle, which can result in weakness or paralysis of the deltoid muscle.
| Characteristics | Values |
|---|---|
| Nerve | Axillary nerve, also known as circumflex nerve |
| Origin | Brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) |
| Carries nerve fibres | C5 and C6 |
| Function | Supplies motor innervation to the deltoid muscle and the skin over the deltoid |
| Injury | Axillary nerve palsy, paralysis of the deltoid muscle, loss of abduction of arm, weak flexion, extension and rotation of shoulder, flat shoulder deformity, loss of sensation in the skin over the regimental badge area |
| Testing | Patient pushes against resistance with the arm beyond 15 degrees of abduction |
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What You'll Learn
- The axillary nerve is the main supplier of innervation to the deltoid muscle
- The axillary nerve can be damaged by trauma to the proximal humerus or shoulder girdle
- The axillary nerve carries sensory information from the shoulder joint
- The axillary nerve can be injured in anterior-inferior dislocations of the shoulder joint
- The axillary nerve divides into anterior and posterior branches to supply the deltoid muscle
The axillary nerve is the main supplier of innervation to the deltoid muscle
The deltoid muscle is a large shoulder muscle and its principal abductor. It is innervated by one of the main branches of the brachial plexus, the axillary nerve. The axillary nerve is formed within the axilla area of the upper limb and is a direct continuation of the posterior cord from the brachial plexus. It carries nerve fibres from C5 and C6 nerve roots.
The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein to innervate the deltoid and teres minor. The nerve lies at first behind the axillary artery and in front of the subscapularis, and passes downward to the lower border of that muscle. It then winds around the surgical neck of the humerus, in company with the posterior humeral circumflex artery, through the quadrangular space.
The axillary nerve divides into anterior and posterior branches to supply the deltoid muscle and the skin over the deltoid. The anterior branch supplies the clavicular and acromial portions, while the spinal head receives innervation from the posterior branch. The axillary nerve also carries sensory information from the shoulder joint. It innervates the skin, covering the inferior region of the deltoid muscle, known as the regimental badge area.
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The axillary nerve can be damaged by trauma to the proximal humerus or shoulder girdle
The axillary nerve is a major peripheral nerve of the upper limb. It is the most commonly injured nerve in the shoulder and is particularly susceptible to injury due to its anatomical relation in the quadrangular space on the posterior scapula. The axillary nerve can be damaged by trauma to the proximal humerus or shoulder girdle. Common mechanisms of injury include fracture of the humeral surgical neck, shoulder dislocation, or iatrogenic injury during shoulder surgery.
The axillary nerve originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibres from C5 and C6. It travels through the quadrangular space, a gap in the muscles of the posterior scapular region, along with the posterior circumflex humeral artery and vein. This space is bounded by the surgical neck of the humerus, with the nerve passing around it.
When the axillary nerve is damaged, the patient may experience paralysis of the teres minor muscle and deltoid muscle, resulting in a loss of abduction of the arm (from 15 to 90 degrees), weak flexion, extension, and rotation of the shoulder. This paralysis can result in a flat shoulder deformity. There may also be a loss of sensation in the skin over the regimental badge area, which is the inferior region of the deltoid muscle.
The axillary nerve is responsible for the motor and sensory functions of the deltoid and teres minor muscles. It provides the ability to abduct the arm at the glenohumeral joint. An inability to abduct the arm beyond 15 degrees may indicate an injury to the axillary nerve. Chronic lesions of the axillary nerve can result in permanent numbness at the lateral shoulder region, muscle atrophy, and neuropathic pain.
It is important to note that the clinical presentation of axillary nerve dysfunction can vary and may be masked by accompanying injuries such as dislocation or fracture. Early detection of axillary nerve injury is crucial as the prognosis is good due to the short recovery time needed for nerve regeneration. Treatment options include immobilization, ROM exercises, strength training, neuromuscular re-education, and functional rehabilitation.
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The axillary nerve carries sensory information from the shoulder joint
The axillary nerve is a nerve in the human body that carries nerve fibres from C5 and C6. It originates from the brachial plexus, a network of nerves in the shoulder, and travels through the quadrangular space to innervate the deltoid and teres minor muscles. The axillary nerve is responsible for causing movement and sensation in the shoulder and the back of the upper arm. It provides motor function to the anterior and posterior deltoid muscles, allowing for abduction of the upper limb at the glenohumeral joint.
The axillary nerve can be injured through various mechanisms, including anterior-inferior dislocations of the shoulder joint, compression of the axilla with a crutch, or fracture of the surgical neck of the humerus. Injury to the axillary nerve can result in paralysis of the deltoid and teres minor muscles, leading to a loss of abduction of the arm and a flat shoulder deformity. It can also cause a loss of sensation in the skin over the regimental badge area.
The axillary nerve is important in the innervation of the deltoid muscle, which is a large shoulder muscle and its principal abductor. The deltoid muscle receives a rich vascular supply from various sources, including branches of the axillary artery. Proper testing of the function of the deltoid muscle is important to accurately determine muscular or nervous injuries. This involves abduction of the arm beyond 15 degrees, at which point the patient pushes against resistance.
In summary, the axillary nerve carries sensory information from the shoulder joint, specifically from the skin over the inferior deltoid muscle, and plays a crucial role in the movement and sensation of the shoulder and upper arm. Injuries to the axillary nerve can have significant effects on the function and sensation of the shoulder and surrounding muscles.
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The axillary nerve can be injured in anterior-inferior dislocations of the shoulder joint
The axillary nerve is a nerve in the human body that originates from the brachial plexus at the level of the axilla (armpit). It carries nerve fibres from C5 and C6 and travels through the quadrangular space with the posterior circumflex humeral artery and vein to innervate the deltoid and teres minor. The nerve supplies two muscles in the arm: the deltoid and the teres minor.
The axillary nerve is susceptible to injury in several ways, including anterior-inferior dislocations of the shoulder joint. The nerve is at risk during shoulder dislocations due to its close proximity to the shoulder capsule and constrained anatomical relationship with the humeral neck and quadrilateral space. During a shoulder dislocation, the axillary nerve can become overstretched, leading to increased tension and possible avulsion from the posterior cord of the brachial plexus. This can result in axillary nerve palsy, characterised by loss of movement or sensation in the shoulder area.
In addition to dislocations, the axillary nerve can also be injured through compression of the axilla with a crutch or fracture of the surgical neck of the humerus. The risk of nerve injury increases with age, and certain activities such as participation in sports or high-impact upper body movements can also increase the likelihood of shoulder dislocation and subsequent nerve injury.
The diagnosis of axillary nerve injury can be challenging due to the delayed onset of symptoms, which may not appear until one to two years post-dislocation. Sensory examinations have low sensitivity in detecting axillary nerve injury, and electrodiagnostic evaluations may be necessary for accurate diagnosis. Treatment options for axillary nerve injuries vary, with immobilisation, ROM-focused treatments, strength training, neuromuscular re-education, and functional therapies being common approaches. Early detection of axillary nerve injuries generally leads to a good prognosis due to the short regeneration and recovery time.
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The axillary nerve divides into anterior and posterior branches to supply the deltoid muscle
The axillary nerve is a major peripheral nerve of the upper limb. It originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibres from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein to innervate the deltoid and teres minor. The nerve passes medially to the surgical neck of the humerus, where it divides into three terminal branches: the anterior branch, the posterior branch, and the articular branch.
The anterior branch (also called the upper branch) winds around the surgical neck of the humerus, beneath the deltoid muscle, with the posterior humeral circumflex vessels. It continues as far as the anterior border of the deltoid to provide motor innervation. The anterior branch also gives off small cutaneous branches, which pierce the muscle and supply the overlaying skin.
The posterior branch (also known as the lower branch) supplies the teres minor and the posterior part of the deltoid. This branch pierces the deep fascia and continues as the superior (or upper) lateral cutaneous nerve of the arm, which sweeps around the posterior border of the deltoid and supplies the skin over the lower part of the deltoid.
The articular branch supplies the glenohumeral joint. The axillary nerve is susceptible to injury, which can result in paralysis of the deltoid and teres minor muscles, leading to a loss of abduction of the arm and a flattened shoulder appearance.
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Frequently asked questions
The axillary nerve, also known as the circumflex nerve, is responsible for the deltoid muscle.
The axillary nerve is a nerve in the human body that carries both motor and sensory information. It originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit).
Injury to the axillary nerve can result in paralysis of the deltoid muscle, leading to a loss of abduction of the arm. It can also cause weak flexion, extension, and rotation of the shoulder.
To test the function of the deltoid muscle, the arm must be abducted beyond 15 degrees. The patient then pushes against resistance. If the muscle is functioning properly, contraction of the muscle should be felt near the acromion of the scapula.
