Extensor Pollicis Longus

Doubling of this muscle is frequent, and the ulnar portion may pass beneath the dorsal ligament with the common extensor. It has been reported the this muscle is absent in about 1.5% of individuals.

Macalister reported the variations of this muscle as follows:

1. It may receive a slip of extensor digitorum communis which runs in the same in the radius (wood); 2. Macalister found the muscle doubled with both tendons inserting as usual; 3. Giving a slip to the base of the first phalanx in a case where extensor pollicis longus was absent; 4. A slip from the extensor pollicis longus to the first phalanx coexisting with a slip from extensor pollicis brevis to the second phalanx.

A slip from the tendon of the long extensor to extensor indicis is seen occasionally. A rarer variation is an additional extensor between extensor indicis and extensor pollicis longus, with a doubled tendon and insertion onto both digits. See paragraph on extensor indicis proprius.This additional extensor may replace extensor pollicis longus or extensor indicis.

Extensor pollicis et indicisis a remarkable muscle occasionally found, and whose homologue is common among other groups of animals including the dog, fox, wolf, jackel, panther, and the dingo; it has been described by Wood, Clason and by Macalister. Its most common arrangement is an origin fron the ulna between the extensor indicis and extensor pollicis longus (with which it usually coexists); it usually is also connected to the interosseous ligament and to the intermuscular septa; its tendon passes downward and divides into two, one to the thumb, and the other to the index finger; sometimes the former runs into the indicial tendon of the extensor communis, while the latter passes to the first phalanx of the thumb, or one is inserted into the first phalanx of the index finger (Wood), or one has been seen joing the extensor pollicis brevis tendon, or substitute for it, or inserted into the second and third phalanges of the index finger, or into the common extensor aponeurosis of the index, or with the extensor pollicis longus. It has also been found arising from the intermuscular septum between the extensor digitorum communis and the extensor pollicis longus, forming a layer intermediate between them, and at first sight apparently connected with the common extensor; this case was inserted, with the tendon of the extensor of the distal phalanx of the thumb; and with the lateral of the two tendons of a doubled indicator. Abductor pollicis tertius (extensor atque abductor pollicis accessorius), a rare muscle, arises from the dorsal aspect of the radius with abductor pollicis longus and inserts, after fusion with abductor pollicis brevis, onto the first metacarpal.

Syn.: m. exttensor. pollicis. major, extensor. secundi internodii pollicis.

Riferimenti dell’opera originale

Elenco riportato come compare nella fonte, senza normalizzazione dei formati bibliografici.

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