Dominic Stone
The infraspinatus muscle is a thick triangular muscle that occupies the dorsal surface of the scapula and is one of the four rotator cuff muscles. Its main function is to externally rotate the humerus and stabilize the shoulder joint. This muscle is innervated by the suprascapular nerve, which arises from the upper trunk of the brachial plexus, derived from roots C5 and C6. The suprascapular nerve provides motor information to the infraspinatus and supraspinatus muscles, and injury to this nerve can result in a loss of function in both muscles, leading to weaker abduction and external rotation of the arm.
| Characteristics | Values |
|---|---|
| Innervation | Suprascapular nerve |
| Nerve Roots | C4, C5, C6 |
| Nerve Branches | Ventral rami, Anterior and posterior divisions of the brachial plexus |
| Function | External rotation of the humerus, Stabilization of the shoulder joint |
| Attachments | Infraspinous fossa of the scapula, Greater tubercle of the humerus |
| Blood Supply | Suprascapular and circumflex scapular arteries |
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What You'll Learn
The infraspinatus muscle is innervated by the suprascapular nerve
The infraspinatus muscle is a thick, triangular muscle that occupies the dorsal surface of the scapula. It is one of the four rotator cuff muscles, along with the subscapularis, teres minor, and supraspinatus muscles. The main function of the infraspinatus muscle is to externally rotate the humerus and stabilize the shoulder joint.
The suprascapular nerve runs through the posterior triangle of the neck and travels across the top of the scapula to pass through the scapular notch. It then travels down the posterior scapula and continues through the spinoglenoid notch to innervate the infraspinatus muscle. This nerve also supplies the supraspinatus muscle, which is located superior to the infraspinatus and is considered one functional unit due to their close anatomical relation.
Traumatic injury to the suprascapular nerve within the posterior triangle of the neck can cause a loss of function in both the supraspinatus and infraspinatus muscles, resulting in weaker abduction and external rotation of the arm. Nerve entrapment may occur at the spinoglenoid or suprascapular notch, and early exploration and characterization of the injury are recommended if nerve laceration is suspected.
In summary, the infraspinatus muscle, which plays a crucial role in external rotation and stabilization of the shoulder joint, receives its innervation from the suprascapular nerve. This nerve arises from the brachial plexus and supplies both sensory and motor information to the infraspinatus and other muscles in the shoulder region.
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The nerve branches off the upper trunk of the brachial plexus
The infraspinatus muscle is one of the four rotator cuff muscles that externally rotate the humerus and stabilise the shoulder joint. It is innervated by the suprascapular nerve, which arises from the upper trunk of the brachial plexus. This nerve provides motor information to the infraspinatus and supraspinatus muscles, allowing them to function properly.
The suprascapular nerve is responsible for the abduction and external rotation of the arm. It branches off the upper trunk of the brachial plexus, derived from roots C5 and C6. The nerve then runs laterally across the lateral cervical region to supply the infraspinatus and supraspinatus muscles.
The brachial plexus is a network of nerves that originate from the spinal cord and supply the arm and shoulder. It is formed by the anterior rami of the lower four cervical nerves (C5-T1) and the upper thoracic nerve. The brachial plexus provides motor and sensory functions to the shoulder and arm, including movement and feeling.
The suprascapular nerve is particularly susceptible to injury, especially within the posterior triangle of the neck. Trauma to the shoulder or nerve entrapment can cause suprascapular neuropathy, resulting in chronic pain and weakness in the infraspinatus and supraspinatus muscles. Early diagnosis and treatment are crucial in managing this condition.
In summary, the infraspinatus muscle is innervated by the suprascapular nerve, which branches off the upper trunk of the brachial plexus. This nerve is essential for the proper functioning of the infraspinatus and supraspinatus muscles, providing motor information and enabling the abduction and external rotation of the arm.
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The nerve traverses the suprascapular notch
The infraspinatus muscle is one of the four rotator cuff muscles that externally rotate the humerus and protect the shoulder joint. The suprascapular nerve, which arises from the upper trunk of the brachial plexus, innervates the infraspinatus muscle. The nerve traverses the suprascapular notch, supplying the supraspinatus muscle, and then descends through the spinoglenoid notch to innervate the infraspinatus muscle.
The suprascapular nerve provides motor information to the infraspinatus and supraspinatus muscles, allowing them to abduct and laterally rotate the arm. The nerve runs through the posterior triangle of the neck, passing under the trapezius muscle, before reaching the supraspinatus muscle through the suprascapular notch. This nerve is susceptible to trauma, which can result in the loss of function of both the supraspinatus and infraspinatus muscles.
The suprascapular nerve is composed of the C5 and C6 nerve roots, with contributions from the C4 nerve in some cases. The C5 nerve is the major contributor to the suprascapular nerve, with a larger mean diameter than the other components. The nerve provides efferent innervation to the supraspinatus and infraspinatus muscles, as well as sensory innervation to the shoulder joint.
Traumatic injury to the suprascapular nerve can cause weakness in abduction and external rotation of the arm, although movement is still possible due to the assistance of other muscles. Nerve entrapment may occur at the suprascapular or spinoglenoid notch, and early exploration and characterization of the injury are recommended in cases of suspected nerve laceration.
The infraspinatus muscle is located in the shoulder joint and plays a crucial role in providing stability and enabling external rotation of the arm. The muscle originates from the infraspinous fossa of the scapula and attaches to the greater tubercle of the humerus. The suprascapular nerve innervates this muscle, making it susceptible to tendinitis due to overuse or misuse.
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The nerve descends through the spinoglenoid notch
The infraspinatus muscle is a thick, triangular muscle that occupies the dorsal surface of the scapula. It is one of the four muscles that comprise the rotator cuff of the shoulder. The suprascapular nerve, which arises from the upper trunk of the brachial plexus, innervates the infraspinatus muscle.
The suprascapular nerve branches off the upper trunk of the brachial plexus and runs through the posterior triangle of the neck. It then travels across the top of the scapula and passes through the scapular notch. The nerve then travels down the posterior scapula and innervates the supraspinatus muscle.
The nerve then continues its course through the spinoglenoid notch to innervate the infraspinatus muscle. The spinoglenoid notch is a small opening located on the posterior aspect of the scapula, just below the spine of the scapula. The suprascapular nerve descends through this notch to reach the infraspinatus muscle, which lies on the dorsal surface of the scapula.
The infraspinatus muscle is susceptible to tendinitis due to overuse and misuse. Trauma to the shoulder can cause suprascapular neuropathy, resulting in chronic pain in the posterior shoulder and weakness in the infraspinatus and/or supraspinatus muscles. Nerve entrapment may occur at the spinoglenoid notch, leading to pain and potential loss of function in the infraspinatus muscle.
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Trauma to the nerve can cause loss of muscle function
The infraspinatus is a thick, triangular muscle that makes up a large part of the infraspinatous fossa. It is one of the four muscles of the rotator cuff, and its main function is to externally rotate the humerus and stabilise the shoulder joint. The suprascapular nerve innervates the infraspinatus muscle.
Traumatic nerve damage can result in muscle weakness, atrophy, and functional deficits. This can be prevented by maintaining a healthy neuromuscular junction, which is critical for nervous control of muscles. A technique called TENS has been found to have a positive effect on maintaining neuromuscular junction health and preventing muscle atrophy.
In severe cases of nerve damage, surgery may be required. This may involve nerve grafting, nerve regeneration, or tendon or muscle transfer. To determine the extent of nerve damage, a doctor may order an electrical conduction test, such as electromyography or nerve conduction velocity.
It is important to note that muscle care is crucial to prevent damage to muscle units. This includes preventing heat or cold trauma, overstretching, and contractures of muscles. Additionally, when performing muscle-strengthening exercises, it is essential to be cautious and not put too much strain on the healing nervous tissue.
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Frequently asked questions
The infraspinatus muscle is innervated by the suprascapular nerve.
The suprascapular nerve branches off the upper trunk of the brachial plexus.
Trauma to the suprascapular nerve will cause the loss of both the supraspinatus and infraspinatus functions. Both abduction and external rotation of the arm will be weaker.
