Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: P: Pronator Quadratus

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Illustrated Encyclopedia of Human Anatomic Variation: Opus I: Muscular System: Alphabetical Listing of Muscles: P

Pronator Quadratus

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

In very rare instances, even when the radius is normal, the absence of a pronator quadratus has been noted. It is occasionaly laminated into two or more layers consisting of fasciculi running in different directions. It may be continued down on the carpus or metacarpus, in some cases as a radiocarpal fasciculus, in other cases as an ulnocarpal fasciculus. Aberrant fibers arising from the distal edge of the muscle may insert into a thenar muscle mass and act as an accessory adductor of the thumb. Pronator quadratus may also extend in a proximal direction on the radius and may be joined to pronator teres or to a flexor carpi radialis brevis.

Radiocarpeus (radiocarpien [Fano], court radial anterieur [LeDouble], flexor carpi radialis brevis vel profundus [Wood], flexor carpi radialis brevis) is a small penniform muscle, present in about 5% of individuals (all sources), which arises from the lateral or ventral surface of the distal half of the radius (usually from its volar border and surface) proximal to pronator quadratus.but occasionaly with some fibers from it. It may extend proximally to the ulna or medial epicondyle and have additional attachment sites. It is inserted by a tendon on one or more carpal bones or on one or more metacarpals, or on both, and occasionally onto the proximal phalanx of the index finger. It is innervated by the anterior interosseous nerve and may be represented as the tibialis posterior of the leg.

Ulnocarpeus brevis (flexor carpi ulnaris brevis or cubitocarpeus) is a small muscle, of rare occurence, corresponding to and resembling the previously described radial muscle. It arises from the ulna, on its medial or volar surface, and is inserted onto the pisiform bone, the hamulus, the proximal end of the fifth metacarpal, the capsule of carpal articulations, or abductor digiti quinti. Mori reported finding this muscle 4 times in 205 arms (1.9%).

Radiocubitocarpien (Calori) (radialis internus brevis biceps) arises from two heads, from the radius and the ulna, and terminates distally on the carpus.

Radiopalmar arises from the anterior face of the radius and superior border of the flexor retinaculum and terminates on the deep surface of the palmar aponeurosis.

Tensor capsulae radiocubitalis (inferioris) is a small muscular slip that arises from the volar aspect of the distal radius, crosses superficial to pronator quadratus in a distal direction, and inserts into the radioulnar capsule

Uncipisiformis (or pisiuncinatus) is a short muscle that extends from the pisiform to the tip of the hamulus of the os hamatum, parallel with the pisohamate ligament. It is innervated by the ulnar nerve. See also abductor digiti minimi.

Syn.: m. pronator inferior (Meckel), Viereckiger Vorwärtswender, Carré pronateur (Cruveilhier).

Radialis Internus Brevis Biceps, Cubitocarpeus, and Supernumerary Head of Abductor Digiti Minimi.
n, radialis internus brevis biceps; n', larger head arose from the radius; n", smaller supernumerary head arose from the forearm aponeurosis; o, cubitocarpeus; p, supernumerary head of abductor digiti minimi.
from Gruber, 1872c.

Cubitoradiocarpien.
a,b, the two heads of cubitoradiocarpien. a, radial head; b, ulnar head; c, tendon of this muscle, insertion in two parts; d, radial eminence of the os trapezium, and e, palmar fascia of os trapezoideum. from Calori.

References

Anson, B.J., Ed. (1966) Morris' Human Anatomy, 12th ed. The Blakiston Division, McGraw-Hill Book Company, New York.

Calori, L. (1870) Degli usi del muscolo pronatore quadrato e di un muscolo sopranumerario cubito-radio-carpeo nell'uomo. Mem. R. Accad. Sci. Instituto di Bologna S. 2. 10:647-657.

Carleton, A. (1934-35) Flexor carpi radialis brevis vel profundus. J. Anat. 69:292-293.

Gruber, W. (1872a) Ein spanner der unteren Radiocubitalkapsel: tensor capsulae radiocubitalis inferioris. Arch. Path. Anat. Physiol. Klin. Med. 54:186-187.

Gruber, W. (1872b) Sur les varietes du muscle radial interne court. Bull. l'Acad. Imp. Sci. St. Petersburg 17:379-380.

Gruber, W. (1872c) Nachträge zu den Varietäten des Musculus radialis internus brevis. Bull. l'Acad. Imp. Sci. St. Petersbourg. 17:380-388.

Gruber, W. (1881) Ein musculus ulnaris externus brevis beim Menschen. Arch. Path. Anat. Physiol. Klin. Med. 86:15-19.

Gruber, W. (1885) Der musculus ulno-carpeus externus (eine neue Variante des Musculus ulnaris externus brevis) und sein Homologen, der musculus peroneo-cuboideus. Arch. Path. Anat. Physiol. Klin. Med. 99:475-478.

Gruber, W. (1885) Ein musculus tensor ligamenti carpi dorsalis. Arch. Path. Anat. Physiol. Klin. Med. 101:259-260.

Gruber, W. (1886) Ein Tensor capsulae radio-carpalis dorsalis. Arch. Path. Anat. Physiol. Klin. Med. 103:474-475.

Henle, J. (1871) Handbuch der Muskellehre des Menschen, in Handbuch der systematischen Anatomie des Menschen. Verlag von Friedrich Vieweg und Sohn, Braunschweig.

Jarjavay, -. (1857) Un muscle surnuméraire de lavant bras. Bulletins et Mem. de la Société Anatomique de Paris XXXII(4)121-122.

Jeffery, A.K. (1971) Compression of the deep palmar branch of the ulnar nerve by an anomalous muscle: Case report and review. J. Bone Joint Surg. B 53:718-723.

Macalister, A. (1871) The varieties of the pronator quadratus. J. Anat. Physiol. 5:32-34.

Macalister, A. (1875) Observations on muscular anomalies in the human anatomy. Third series with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-130.

Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.

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