The anconeus muscle (or anconaeus/ anconæus) is a small muscle on the posterior aspect of the Elbow-joint joint.
Some consider anconeus to be a continuation of the triceps brachii muscle.[Williams, P. et al., 1995, Gray's Anatomy, 38th ed., Churchill Livingstone][Jones, W. et al. (eds), 1953, Buchanan's Manual of Anatomy, 8th ed., Balliére, Tindall and Cox., pp. 496][Grant, J. & Basmajian J., 1965, Grant's Method of Anatomy, 7th ed., The Williams & Wilkins Company, Baltimore, pp. 163-164] Some sources consider it to be part of the posterior compartment of the arm,
The anconeus muscle can easily be palpated just lateral to the olecranon process of the ulna.
Structure
Anconeus originates on the posterior surface of the lateral epicondyle of the humerus and inserts distally on the superior posterior surface of the ulna and the lateral aspect of the olecranon.
Innervation
Anconeus is innervated by a branch of the
radial nerve (cervical roots 7 and 8)
from the posterior cord of the
brachial plexus called the nerve to the anconeus. The somatomotor portion of radial nerve innervating anconeus bifurcates from the main branch in the radial groove of the
humerus. This innervation pattern follows the rules of innervation of the musculature of the posterior forearm (extensor) compartment by the radial nerve.
Function
Its role in elbow extension is trivial in humans. It assists in extension of the elbow, where the triceps brachii is the principal agonist, and supports the elbow in full extension.
It also prevents the elbow joint capsule being pinched in the
olecranon fossa during extension of the elbow. Anconeus also abducts the ulna and stabilizes the elbow joint. Anconeus serves to make minute movements with the radius on the
ulna. In making slight abduction of the ulna, it allows any finger to be used as an axis of rotation of the forearm.
Blood supply
Anconeus is supplied by the middle collateral artery from the profunda brachii artery.
Clinical significance
Trauma to the nerve supply of the anconeus muscle can usually result from a shoulder dislocation or fractures of the upper part of the
humerus or around the
olecranon, or any injury that damages the radial nerve. Harm inflicted upon the radial nerve through these mechanisms can paralyze the anconeus muscle as well as other extensors of the
elbow and
wrist.
There are no specific acquired injuries that exclusively affect the anconeus muscle; however, any disease that compromises muscular functions, particularly arm extension (i.e. muscular dystrophy) will affect this particular accessory muscle. Heterotopic ossification can result from certain trauma as it is an abnormal growth of osseous tissue in non-osseous tissue (e.g. muscle tissue). The condition is usually found in the hips, although there have been documented cases of certain individuals with it occurring in the arms and legs. The cause for the process to initiate is not well understood, only that it typically results from surgery or trauma.
History
Etymology and spelling
Anconeus muscle is the anglicized form of the Latin expression
musculus anconaeus, as can be found in the
Nomina Anatomica as ratified in
Basel in 1895
[His, W. (1895). Die anatomische Nomenclatur. Nomina Anatomica. Der von der Anatomischen Gesellschaft auf ihrer IX. Versammlung in Basel angenommenen Namen. Leipzig: Verlag Veit & Comp.] and in
Jena in 1935.
[Kopsch, F. (1941). Die Nomina anatomica des Jahres 1895 (B.N.A.) nach der Buchstabenreihe geordnet und gegenübergestellt den Nomina anatomica des Jahres 1935 (I.N.A.) (3. Auflage). Leipzig: Georg Thieme Verlag.][Stieve, H. (1949). Nomina Anatomica. Zusammengestellt von der im Jahre 1923 gewählten Nomenklatur-Kommission, unter Berücksichtigung der Vorschläge der Mitglieder der Anatomischen Gesellschaft, der Anatomical Society of Great Britain and Ireland, sowie der American Association of Anatomists, überprüft und durch Beschluß der Anatomischen Gesellschaft auf der Tagung in Jena 1935 endgültig angenommen. (4th edition). Jena: Verlag Gustav Fischer.] The anatomic Latin adjective
anconaeus was written as
anconeus in the subsequent edition of the
Nomina Anatomica as authorized in 1955 in
Paris,
[International Anatomical Nomenclature Committee (1955). Nomina Anatomica . London/Colchester:Spottiswoode, Ballantyne and Co. Ltd.] without any further explanation of this specific diphthong reduction. The following edition of 1961 specified its policy by stating that:
All diphthongs should be eliminated.
[International Anatomical Nomenclature Committee (1966). Nomina Anatomica. Amsterdam: Excerpta Medica Foundation.] Although a selected number of monophthongizations was reverted, subsequent editions of the
Nomina Anatomica and its most recent outing
Terminologia Anatomica insisted on writing
musculus anconeus.
[International Anatomical Nomenclature Committee (1977). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Amsterdam-Oxford: Excerpta Medica.][International Anatomical Nomenclature Committee (1983). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Baltimore/London: Williams & Wilkins][International Anatomical Nomenclature Committee (1989). Nomina Anatomica, together with Nomina Histologica and Nomina Embryologica. Edinburgh: Churchill Livingstone.][Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica. Stuttgart: Thieme] Despite the earlier preference of the
Nomina Anatomica for
anconaeus no
ancient Greek form ἀγκωναῖος is attested.
[Hyrtl, J. (1880). Onomatologia Anatomica. Geschichte und Kritik der anatomischen Sprache der Gegenwart. Wien: Wilhelm Braumüller. K.K. Hof- und Universitätsbuchhändler.] In
modern Greek the expression ἀγκωνιαίος μυς
[Schleifer, S.K. (Ed.) (2011). Corpus humanum, The human body, Le corps humain, Der menschliche Körper, Il corpo umano, El cuerpo humano, Ciało człowieka, Människokroppen, Menneskekroppen, Τό ανθρώπινο σῶμα, ЧЕЛОВЕК. FKG.] is used, with the from
anconaeus deviating adjective ἀγκωνιαίος.
[Triepel, H. (1910). Die anatomischen Namen. Ihre Ableitung und Aussprache. Mit einem Anhang: Biographische Notizen.(Dritte Auflage). Wiesbaden: Verlag J.F. Bergmann.]
Anconaeus is derived from the ancient Greek noun, ἀγκών.[Kraus, L.A. (1844). Kritisch-etymologisches medicinisches Lexikon (Dritte Auflage). Göttingen: Verlag der Deuerlich- und Dieterichschen Buchhandlung.][Liddell, H.G. & Scott, R. (1940). A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with the assistance of. Roderick McKenzie. Oxford: Clarendon Press.] or elbow.[Barker, L.W. (1907). Anatomical terminology with special reference to the BNA. With vocabularies in Latin and English and illustrations. Philadelphia: P. Blakiston's Son & Co.] of the first edition of the Nomina Anatomica.
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