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

Abductor Pollicis Longus

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

Variations in the muscles of the thumb have been reported to occur in one of every six subjects dissected. The most common variations occur in the long abductor and consist of an extensive cleavage of its tendon, or even the whole muscle, into separate parts. The belly of the muscle may be doubled. The long abductor may be reduced to a small slip arising only from the radius. The abductor pollicis longus may also arise from both the ulna and the mediolateral aspect of the radius. The slips into which its tendon is divided may find attachment to the flexor retinaculum, scaphoid, trapezium, abductor pollicis brevis, opponens pollicis, first phalanx, or the tendon may be inserted onto the base of the first metacarpal bone. An additional tendon may give origin to opponens pollicis. In one study of 134 wrists, 132 (95%) abductor pollicis longus muscles had accessory tendons. They inserted into abductor pollicis brevis in 25%; the trapezium, joint capsule, fascia in 34%; and the trapezium, joint capsule, and the abductor pollicis brevis muscle in 39%. The insertion of the abductor pollicis longus tendon varied in almost every instance from anatomy textbook descriptions. These involved, in addition to the base of the first carpometacarpal joint, the trapezium, navicular (scaphoid), surrounding fascial structures or the abductor pollicis brevis muscle. In another study of 38 forearms, only seven abductor pollicis longus muscles had a single tendon, the usual condition, 19 had an additional tendon, 20 had two, and six had three anomalous tendons. In the 19 cases with a second tendon, the aberrant tendon inserted into the tendon of abductor pollicis brevis in 12 cases, inserted onto the trapezium in six, and joined the volar carpal ligament in one. In the 20 cases of doubled aberrant tendon, 10 inserted into the abductor pollicis brevis, eight inserted onto the trapezium, and two inserted into the opponens pollicis. In the six cases of triple aberrant tendon, two tendons inserted into the abductor pollicis brevis, two inserted onto the trapezium, and two inserted into the tendon of opponens pollicis. In another study of 127 dissected forearms, 10.2% of the abductor pollicis longus muscles had a single tendon that inserted upon the radial side of the first metacarpal only. In the remaining 89.8%, the abductor had a dual insertion: into the abductor pollicis brevis, 56%; onto the trapezium, 18%; into the opponens pollicis, 15.7%; onto the first phalanx of the thumb, 7.1%; and into the carpal-metacarpal joint, 2.3%.

Macalister reported the following variations of extensor ossis metacarpi pollicis (abductor pollicis longus):

1. It very often has a double tendon both inserted together;
2. Or one is inserted onto the trapezium connected to the tendon of the short abductor pollicis (brevis). This not uncommon and occurs about once in every 12 subjects;
3. A triple tendon-two into the metacarpal and one into the trapezium;
4. A triple tendon, one into the metacarpal, one into the trapezium, and one into the opponens pollicis;
5. Or two into the metacarpal and one into the opponens pollicis;
6. Cloquet found it sending a slip into the origin of abductor pollicis brevis. Mr. Wood found this 7 times in thirty six subjects (1867);
7. A doubled muscle, one-half of which went exclusively to the abductor pollicis;
8. A triple tendon like No. 4, which sent a slip to abductor pollicis;
9. An example with four tendons, three to the metacarpal bone, and one to the abductor indicis (Macalister);
10. The muscle has been found fused with the extensor primi internodii (extensor pollicis brevis);
11. A doubled muscle with normal insertion;
12. A double muscle, the inner (medial) segment of which was normal, the outer (lateral) had four tendons, three of which go into the first metacarpal bone, and one gave origin to part of the opponens pollicis;
13. Macalister found the muscle fused with extensor primi (extensor pollicis brevis), and giving off two tendons;
14. Mr. Carver found it in a idiot, with three slips from a single tendon, one to the distal phalanx of the thumb, one to the second phalanx, and one to the scaphoid bone;
15. Fleischmann describes it as digastric, but the case seems to be rather one of the examples of the extensor carpi radialis accessorius; a digastric example is also described by Sömmerring;
16. Macalister has found it doubled; one muscle with four tendons, one to the trapezium, one to the lateral part of abductor brevis pollicis, one to the opponens, and the fourth to the metacarpal; the second went entirely to the metacarpal bone; this co-existed with a slip from the extensor secundi (extensor pollicis longus) to the first phalanx;
17. Macalister found a slip inserted into the annular ligament.

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. abductor pollicis bicornis, m. extensor ossis metacarpi pollicis (Sharpey).

Variations of abductor pollicis longus tendons of insertion.
a, usual tendon of insertion at base of the first metacarpal;
b, tendinous slip to the greater multangular;
c, tendinous slip to abductor pollicis brevis; and
d, tendinous slip to opponens pollicis.
From Lacey, et al. (1951)

Accessory abductor pollicis longus.
An accessory muscular slip to abductor pollicis longus had its origin from the tendon of brachioradialis.
from Calori, 1867

References

Abu-Hijleh, M.F. (1993) Extensor pollicis tertius: an additional extensor muscle to the thumb. Plast. Reconstructive Surg. 92:340-343.

Baba, M.A.(1954) The accessory tendon of the abductor pollicis longus muscle. Anat. Rec. 119:541-574.

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

Brottet, -. (1876) Long abducteur et court abducteur du pouce, surnuméraires. Lyon Med. 21:475.

Calori, L. (1867) Di alcune varieta muscolari dell'avambraccio e dell' eminenza ipothenar. Mem. de Accad d. Scienze d. Istituto di Bologna. S. 2. VII: 359-381.

Chopra, R.P., Singh, S.,and S.S. Makhni. (1954-55) The insertion of the abductor pollicis longus and extensor pollicis brevis. J. Anat. Soc. India 7:105-109.

Coleman, S.S., Macafee, D.K., B.J. Anson. (1953) The insertion of the abductor pollicis longus muscle. An anatomical study of 175 specimens. Q. Bull. Northwestern Univ. Med. Sch. 27:117-122.

Debierre, C. (1888) Anomalie des muscles radiaux externes et du long abducteur du pouce de l'homme. Soc. Biol., Comptes Rendus Hebdomadaires des Séances et Mémoires. 40:547-550.

Giles, K.W. (1960) Anatomical variations affecting the surgery of De Quervain's disease. J. Bone Joint Surg. 42B: 352-355.

Imaeda, T. and W.P. Cooney (1992) Functional anatomy and biomechanics of the thumb. Hand Clinics 8:9-15.

Jackson, W.T., Viegas, S.F., Coon, T.M., Stimpson, K.D., Frogameni, A.D., and J.M. Simpson. (1986) Anatomical variations in the first extensor compartment of the wrist. J. Bone Joint Surg. 68A: 923-926.

Jansen, J.H. (1850) Waarnemingen van anomale spieren. Nederlandsch Lancet 1850:431-437.

Kimura, K. (1958) On the variation of the terminal tendon of the M. abductor pollicis longus. Kaibogaku Zasshi 33:523-527. In Japanese.

Lacy, T. III., Goldstein, L.A., and C.E. Tobin. (1951) Anatomical and clinical study of the variations in the insertions of the abductor pollicis longus tendon, associated with stenosing tendovaginitis. J. Bone Joint Surg. 33A:347-350.

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.

Martinez, R. and G.E. Omer (1985) Bilateral subluxation of the base of thumb secondary to an unusual abductor pollicis longus insertion: a case report. J. Hand Surg. 10A: 396-399.

Oudenaarde, E.V. (1991) Structure and function of the abductor pollicis longus muscle. J. Anat. 174;221-227.

Patel, M.R. and S.S. Desai (1988) Anomalous muscles of the first dorsal compartment of the wrist. J. Hand Surg. 13A:829-831.

Petit, A. (1880) Anomalie musculaire: Un digastric muscle de l'avantbras droit. Bulletins et Mem. de la Société Anatomique de Paris LV(1):114-115.

Pires de Lima, J.A. (1914) Nova série de observações Portugesas de anomalias musculares. Arch. de Anat. e de Anthropol. 1(3):231-260.

Rayan, G.M. and E. Mustafa. (1989) Anomalous abductor pollicis longus insertion in the thenar muscles. J. Hand Surg. (A) 14:550-552.

Schuldt, H.H. (1947-48) Ein zweibäuchiger Musculus abductor tertius des rechten Daumens. Anat. Anz. 96:418.

Shepherd, F.J. (1880) Notes of abnormalities observed in the dissecting-room of McGill University, from October, 1875, to May, 1879. Ann. Report. Montreal General Hospital 1:71-93.

Stein, A.H. (1951) Variations of the tendons of insertion of the abductor pollicis longus and extensor pollicis brevis. Anat. Rec. 110:49-55.

Wood, J. (1867) On human muscular variations in their relation to comparative anatomy. J. Anat. Physiol. 1:44-59.

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