Supinator: Difference between revisions

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'''Original Editor '''- [[User:Kate Sampson|Kate Sampson]],  
'''Original Editor '''- [[User:Kate Sampson|Kate Sampson]],  


'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}};  
'''Top Contributors''' - {{Special:Contributors/{{FULLPAGENAME}}}};   
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== Description [[Image:Supinator 2.png|border|right|200px]] ==


The supinator muscle is located in the posterior compartment of the forearm. As its name suggests, it is the prime supinator of the forearm.<ref>Gray H. ''[https://www.bartleby.com/107/125.html Anatomy of the Human Body.]'' Twentieth edition. Philadelphia: Lea & Febiger; 918 Available from: https://www.bartleby.com/107/125.html [Accessed 23 May 2019]</ref><br>  
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== Description ==
[[File:Supinator muscle.png|thumb|[https://commons.wikimedia.org/wiki/File:Musculussupinator.png Supinator muscle]]]
The supinator muscle is located in the posterior compartment of the forearm. As its name suggests, it is the prime supinator of the forearm.<ref name=":0">Gray H. ''[https://www.bartleby.com/107/125.html Anatomy of the Human Body.]'' Twentieth edition. Philadelphia: Lea & Febiger; 918 Available from: https://www.bartleby.com/107/125.html [Accessed 23 May 2019]</ref><br>  


== Structure  ==
== Structure  ==
is a broad muscle in the posterior compartment of the forearm, curved around the upper third of the radius. Supinator consists of two planes of fibers, between which the deep branch of the radial nerve ls. The two planes arise in common — the superficial one by tendinous (the initial portion of the muscle is actually just tendon) and the deeper by muscular fibers —<sup>[2]</sup> from the supinator crest of ulna, the lateral epicondyle of humerus, the radial collateral ligament, and the annular radial ligament.<sup>[1]</sup>
The supinator is a broadly-shaped muscle in the superior and posterior compartment of the forearm, It curves around the upper third of the radius and consists of two layers of fibres. In between these layers lies the deep branch of the [[radial nerve]].<ref name=":0" />
 
The superficial fibers (''pars superficialis'') surround the upper part of the radius, and are inserted into the lateral edge of the radial tuberosity and the oblique line of the radius, as low down as the insertion of the pronator teres. The upper fibers (''pars profunda'') of the deeper plane form a sling-like fasciculus, which encircles the neck of the radius above the tuberosity and is attached to the back part of its medial surface; the greater part of this portion of the muscle is inserted into the dorsal and lateral surfaces of the body of the radius, midway between the oblique line and the head of the bone.<sup>[2]</sup>
 
The proximal aspect of the superficial head is known as the arcade of Frohse or the supinator arch.


== Origin  ==
== Origin  ==
and has a broad origin from the ulna and humerus and extends down to the posterior surface of the proximal third of the radius.  
The supinator muscle has a broad origin from the [[ulna]] and [[humerus]]. The two layers of fibres originate in common from the supinator crest of the [[ulna]], the lateral epicondyle of the [[humerus]], the radial collateral ligament and the annular radial ligament. The superficial layer of fibres has a tendinous origin and surround the upper part of the radius. The deeper layer of fibres encircles the neck of the [[radius]] above the radial tuberosity.<ref name="Martini" />
 
- Lateral epicondyle of the humerus
 
- Annular ligament
 
- Supinator Cest fossa of the ulna <ref name="Martini" />  


== Insertion  ==
== Insertion  ==


- Proximal third of the radius on the anterolateral surface, distal to the radial tuberosity. <ref name="Martini">Martini FH. Fundamentals of Anatomy and Physiology. Seventh Edition. Pearson Education Inc, 2006.</ref>  
Proximal third of the [[radius]] on the anterolateral and posterior surface, distal to the radial tuberosity. <ref name="Martini">Martini FH. ''Fundamentals of Anatomy and Physiology''. Seventh Edition. Pearson Education Inc; 2006.</ref>


== Innervation  ==
== Innervation  ==


Supinator is supplied by the posterior interosseous brach of the radial nerve (C5, C6) <ref name="Palastanga">Palastanga N, Field D, Soames R. Anatomy and human movement. Structure and function. 5th ed. London: Butterworth Heinemann Elsevier, 2006</ref>
The supinator muscle is innervated by the deep branch of the [[radial nerve]], that becomes the posterior interosseous nerve upon exiting the supinator muscle (C5, C6) <ref name="Palastanga">Palastanga N, Field D, Soames R. ''Anatomy and human movement. Structure and function''. 5th ed. London: Butterworth Heinemann Elsevier; 2006</ref>
 
It is innervated by the deep branch of the radial nerve. The deep branch then becomes the posterior interosseous nerveupon exiting the supinator muscle
 
The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle — an arrangement that can lead to entrapment and compression of the deep part, potentially resulting in selective paralysis of the muscles served by this nerve (the extensor muscles and the abductor pollicis longus.)<sup>[3]</sup> Many possible causes are known for this nerve syndrome, known as supinator entrapment syndrome, including compression by various soft-tissued masses surrounding the nerve, and stress caused by repetitive supination and pronation
 
== Blood Supply ==


== Function  ==
== Function  ==
The main function of the supinator is to supinate the forearm. This can be done with the elbow in any position of flexion or extension. Supinator works with [[Biceps Brachii]] if powerful supination is required. However, [[Biceps Brachii]] is unable to supinate when the elbow is extended.<ref name="Palastanga" />


Supinator supinates the forearm. It causes the distal end of the radius to move anterolaterally around the ulna, causing them to lie paralell <br>
== Clinical Relevance ==
 
The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle. This can lead to entrapment and compression of the deep branch and could potentially result in selective paralysis of the muscles served by this nerve. Many possible causes are known for this nerve syndrome (known as supinator entrapment syndrome) including compression by various soft-tissued masses surrounding the nerve, and stress caused by repetitive supination and pronation<br>
Supinator works with biceps brachii if powerful supination is required. However biceps brachii is unable to function to supinate when the elbow is extended<ref name="Palastanga" />
 
Encircling the radius, supinator brings the hand into the supinated position. In contrast to the biceps brachii, it is able to do this in all positions of elbow flexion and extension.<sup>[1]</sup>
 
Supinator always acts together with biceps, except when the elbow joint is extended.<sup>[6]</sup> It is the most active muscle in forearm supination during unresisted supination, while biceps becomes increasingly active with heavy loading. Supination strength decreases by 64% if supinator is disabled by, for example, injury.<sup>[7]</sup>


== Assessment  ==
== Assessment  ==


== Palpation  ==
Place the patient's arm and elbow in extension with the forearm in mid-position. Actively resist supination and palpate along the posterior part of the proximal third of the radius. <ref name="Palastanga" />  
 
Place the patients arm in extension at the elbow and the forearm in midposition. Actively resist supination and palpate along the posterior part of the proximal third of the radius. <ref name="Palastanga" />  


== Resources  ==
== Resources  ==
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[[Category:Anatomy]]
[[Category:Anatomy]]
[[Category:Anatomy Project]]
[[Category:Anatomy Project]]
[[Category:Forearm Anatomy]]
[[Category:Elbow]]
[[Category:Muscles of the Hand and Wrist]]
[[Category:Elbow - Anatomy]]  
[[Category:Elbow - Muscles]]

Latest revision as of 14:57, 10 January 2022

Original Editor - Kate Sampson,

Top Contributors - Kate Sampson, Kim Jackson, Nina Myburg, 127.0.0.1 and Joao Costa;

Description[edit | edit source]

The supinator muscle is located in the posterior compartment of the forearm. As its name suggests, it is the prime supinator of the forearm.[1]

Structure[edit | edit source]

The supinator is a broadly-shaped muscle in the superior and posterior compartment of the forearm, It curves around the upper third of the radius and consists of two layers of fibres. In between these layers lies the deep branch of the radial nerve.[1]

Origin[edit | edit source]

The supinator muscle has a broad origin from the ulna and humerus. The two layers of fibres originate in common from the supinator crest of the ulna, the lateral epicondyle of the humerus, the radial collateral ligament and the annular radial ligament. The superficial layer of fibres has a tendinous origin and surround the upper part of the radius. The deeper layer of fibres encircles the neck of the radius above the radial tuberosity.[2]

Insertion[edit | edit source]

Proximal third of the radius on the anterolateral and posterior surface, distal to the radial tuberosity. [2]

Innervation[edit | edit source]

The supinator muscle is innervated by the deep branch of the radial nerve, that becomes the posterior interosseous nerve upon exiting the supinator muscle (C5, C6) [3]

Function[edit | edit source]

The main function of the supinator is to supinate the forearm. This can be done with the elbow in any position of flexion or extension. Supinator works with Biceps Brachii if powerful supination is required. However, Biceps Brachii is unable to supinate when the elbow is extended.[3]

Clinical Relevance[edit | edit source]

The radial nerve divides into deep and sensory superficial branches just proximal to the supinator muscle. This can lead to entrapment and compression of the deep branch and could potentially result in selective paralysis of the muscles served by this nerve. Many possible causes are known for this nerve syndrome (known as supinator entrapment syndrome) including compression by various soft-tissued masses surrounding the nerve, and stress caused by repetitive supination and pronation

Assessment[edit | edit source]

Place the patient's arm and elbow in extension with the forearm in mid-position. Actively resist supination and palpate along the posterior part of the proximal third of the radius. [3]

Resources[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Gray H. Anatomy of the Human Body. Twentieth edition. Philadelphia: Lea & Febiger; 918 Available from: https://www.bartleby.com/107/125.html [Accessed 23 May 2019]
  2. 2.0 2.1 Martini FH. Fundamentals of Anatomy and Physiology. Seventh Edition. Pearson Education Inc; 2006.
  3. 3.0 3.1 3.2 Palastanga N, Field D, Soames R. Anatomy and human movement. Structure and function. 5th ed. London: Butterworth Heinemann Elsevier; 2006