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

Extensor Carpi Ulnaris

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

a) the muscle is occasionally doubled throughout,

b) there may be a partial attachment of its tendon to the base of the third or fourth metacarpal bone,

c) an additional tendon may replace an absent extensor digiti quinti, and

d) an independent muscle ulnaris digiti minimi or ulnaris digiti quinti has been observed arising from the lower part of the dorsal surface of the ulna and inserting onto the base of the first phalanx of the little finger.

Barfred and Adamsen reported on three cases, in which an anomalous slip between the extensor carpi ulnaris tendon and the extensor apparatus of the fifth finger was found. One of these patients was a violinist who experienced serious impairment of the wrist and little finger. When the variation was removed, the symptoms disappeared. This muscle may be represented by a fasciculus from the belly of the extensor carpi ulnaris, or more frequently (44%) by a dorsal slip from its tendon, which may insert onto the metacarpal bone, first phalanx, or extensor tendon of the little finger. In many cases (52%), a slip extends from the tendon anteriorly over opponens digiti minimi and inserts into the fascia covering the metacarpal bone, the capsule of the metacarpophalangeal joint, or onto the first phalanx of the little finger. The slip is sometimes joined or replaced by a muscular fasciculus arising from, or in the neighborhood of, the pisiform bone. Agenesis of extensor carpi ulnaris is rare (0.55%).

Macalister reported the following:

1. Extensor carpi ulnaris has been found receiving a slip from the triceps;

2. It may send a tendon to replace that of a suppressed extensor minimi digiti;

3. It may give origin, from its tendon, to abductor minimi digiti;

4. It may send a slip to be inserted into the septum in the posterior annular ligament, between its usual insertion and the extensor minimi digiti;

5. It may send a slip to the tendinous aponeurosis, on the back of the little finger (Henle, Meckel, and Wood). Wood stated it had a frequency of 12%. The slip is named ulnaris quinti.

Syn.: m. ulnaris externus, Ellenbogenstrecher der Hand, Aeusserer Ellenmuskel, Cubital posterior (Cruveilheir).

References

Barfred, T. and S. Adamsen. (1986) Duplication of the extensor carpi ulnaris tendon. J. Hand Surg. (A) 11:423-425.

Baumann, J.A. (1947) Valeur, variation, et équivalences des muscles extenseurs, interosseux, adducteurs et abducteurs de la main et du pied chez l'homme. Acta Anat. 4:10-16.

Curnow, J. (1873) Notes of some irregularities in muscles and nerves. J. Anat. Physiol. 7:304-309.

Gloobe, H. and S. Liberty. (1973) Bilateral agenesis of extensor carpi ulnaris. Hand 5:175-176.

Gruber, W. (1885) Mangel des Musculus ulnaris externus bis auf einen Sehnenstreifen. Arch. Path. Anat. Physiol. Klin. Med. 99:478-480.

Macalister, A. (1875) Additional observations on muscular anomalies in human anatomy (third series), with a catalogue of the principal muscular variations hitherto published. Trans. Roy. Irish Acad. Sci. 25:1-134.

Wood, J. (1868) Variations in human myology observed during the winter session of 1867-68 at King's College, London. Proc. Roy. Soc. Lond. B 17:483-485.

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