Extensor Digiti Minimi (Propius) (Manus)

A thin fibrous slip from the lateral epicondyle of the humerus and continuous with the common tendon is occasionally present. More rarely, there is a supplementary origin from the dorsal surface of the ulna. The belly of the muscle may be doubled.

The tendon of insertion is sometimes divided and gives a slip to the fourth digit. An ulnar slip has been observed to end on the base of the fifth metacarpal, thus exactly reproducing the arrangement of the serially homologous slip known as peroneus tertius in the leg. The muscle may be absent in rare cases, but fusion with extensor digitorum is frequent, in which case the tendon comes from the common extensor.

Mori has described an extensor digiti minimi accessorius which occurs when the extensor digiti minimi divides into two slips. The ulnar part extends onto the back of the fifth metacarpal to the base of the first phalanx of the little finger and is the extensor digiti minimi, the radial slip extends to the dorsal carpal ligament and inserts into it and this becomes the extensor digiti minimi accessorius. Mori found this variation in 4% of his subjects. Mori also describes an extensor digiti minimi et quarti, which is present in 2% of his subjects. The terminal tendon of extensor digiti minimi divides into two slips, one extends over the fifth metacarpal to insert onto the proximal phalanx of the little finger, and second slip extends over the fourth metacarpal and fuses with the terminal tendon of extensor digitorum for the fourth finger.

Macalister reported the following variations:

1. The muscle may be absent and substituted by a slip of the extensor communis
2. Or by a slip by the extensor carpi ulnaris
3. Or with no substitute
4. The muscle may have two tendons, both inserted into the little finger (a very common arrangement)
5. It has been found doubled, both muscle and tendon, by Wood and Macalister
6. It may have a double tendon, the lateral one going to the ring finger, and the other to the little finger; cases of this type have been seen by Vesalius, Meckel, M'Whinnie, Hallett, Theile, and Wood. Wood found this variation 13 times in 106 cases, one in every eight individuals. Macalister found it to occur in Irish subjects more than once in 14
7. It was found with a treble tendon, two going to the little finger, and one to the ring finger
8. The muscle may receive an accessory slip from the common extensor (Sömmerring).

Syn.: m. Extensor digiti quinti proprius.

Riferimenti dell’opera originale

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• 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.
• Calori, L. (1867) Di alcune varieta muscolari dell'avambraccio e dell'eminenza ipothenar. Mem. R. Accad. Sci. Istituto di Bologna. S.2, 7:359-381.
• Flower, W.H. and J. Murie. (1867) Account of the dissection of a Bush woman. J. Anat. Physiol. 1:202-208.
• Gruber, W. (1885) Zweibäuchiger Extensor digiti V proprius manus mit Insertion eines seiner Bäuche an die Basis des Metacarpal V, und die ihm homologe Variante des Peroneus III. Arch. Path. Anat. Physiol. Klin. Med. 99:480-483.
• Gruber, W. (1885) Absoluter Mangel des Extensor digiti quinti proprius manus bei mangel seiner Vagina im ligamentum carpi dorsale: ganz ausnahmsweise und nur beim Menschen (2 Fall) bei Vorkommen des muskels dennoch Mangel der Vagina constant bei den Prosimiae. Arch. Path. Anat. Physiol. Klin. Med. 99:484-488.
• Gruber, W. (1885) Duplicität des Musculus extensor digiti quinti et quarti proprius manus. Arch. Path. Anat. Physiol. Klin. Med. 101:260-262.
• 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.
• Mori, M. (1964) Statistics on the musculature of the Japanese. Okajimas Fol. Anat. Jap. 40:195-300.
• Straus, Jr., W.L. and O.Temkin. (1943) Vesalius and the Problem of Variability. Bull. History Med. 14:609-633.
• 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. 17:483-525.