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

Lumbricales (Manus)

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

Wood reported that he found 19 variations in 102 individuals (or 5.3%). They may be reduced to three or even two, and in rare instances all four are absent. Rarely, the number may be increased by the development of accessory slips. In the case of the first lumbrical, an accessory slip may arise from the tendon of flexor pollicis longus, the tendon of fllexor digitorum superficialis, the first metacarpal, opponens pollicis, or the palmar carpal ligament.

Cases have also been observed in which a fasciculus arose from the muscular belly of the superficial or deep flexor and joined the first lumbrical. The second lumbrical may arise from two tendons between which it lies. On the other hand, the third and fourth may arise from one tendon only.

Variations of insertion frequently occur with the third and fourth lumbricals. The origin of one or another of the lumbricals may be displaced proximally, arising from the flexor retinaculum, from a special tendon from the deep or superficial flexor, or, in the case of the first lumbrical, from the tendon of the flexor pollicis longus. They may be attached in the palm to the superficial as well as to the deep flexor tendons.

Frequently, the lumbricals may be bifid distally and insert into two fingers. This occurs in the case of the third lunbrical in about 40% of individuals.

The destination of one or more of the lumbricals may be changed, and one finger sometimes has two lumbricals inserted into it. They may be inserted onto the first phalanx instead of or in addition to the normal attachment to the extensor tendon. The fourth lumbrical has been observed to replace the fourth tendon of flexor superficialis. Mori has provided a statistical evaluation of the lumbrical muscles as follows:

Origin of the lumbrical muscles.

1. The first lumbrical arises from the radial side of the terminal tendon of flexor digitorum profundus for the second finger in 100% of his subjects.
2. The second lumbrical arises from the radial side of the terminal tendon of flexor digitorum profundus for the middle finger in 78%. The second lumbrical arises with two heads. One arises from the radial side of the tendon of flexor digitorum profundus for the middle finger, and the second head arises from the ulnar side of the tendon of flexor digitorum profundus for the second finger in 22 %.
3. The third lumbrical arises with two heads from the opposite surface of the terminal tendons for the middle and fourth fingers in 98% of subjects.
4. The fourth lumbrical arises from the ulnar side of the terminal tendon of flexor digitorum profundus for the fourth finger in 2%.

Insertion of the lumbrical muscles.

1. The tendons of the first and second lumbricals are attached along the side of the first phalanx to the radial border of the tendon of extensor digitorum for the second and third fingers in 10% of subjects
2. The third lumbrical is divided into two slips, and one is inserted on the ulnar surface of extensor digitorum for the fourth finger in 20%. The terminal tendon of the third lumbrical is inserted on the radial surface of extensor digitorum for the fourth finger in 80% of subjects.
3. The fourth lumbrical is divided into two slips, one is inserted on the ulnar surface of extensor digitorum for the fourth finger, and the second is inserted on the ulnar surface of the terminal tendon of extensor digitorum for the fifth finger in 24%
   The fourth lumbrical is inserted on the ulnar surface of extensor digitorum for the fourth finger in 4%.
   The fourth lumbrical is inserted on the radial surface of extensor digitorum for the fifth finger in 96% of subjects.

Macalister reported the varieties as follows:

1. The first lumbrical may be doubled, one being normal, the second arising from the flexor sublimis (digitorum superficialis). A case of this kind was described by Wood, in which the origin of the second flexor was a fine tendon which arose from the outside of the coronoid origin of flexor sublimis. In another case, Wood found the deviant lumbrical split into two parts, the innermost being implanted into the tendon of the perforatus (flexor digitorum superficialis), near its division in the sheath of the index finger, the outer joined the normal lumbricalis, near its usual place of insertion;
2. Macalister and Wood described a slip from flexor pollicis giving a tendon to the first lumbrical. The same author found the first lumbrical arising from flexor digitorum superficialis and the thumb alone. The muscle was bipenniform;
3. A supplementary head for the first lumbrical, originating from the first palmar interosseous was found by Wood;
4. The first has been seen inserted the second finger by Moser;
5. Macalister reports that the first lumbrical may be absent;
6. The second may also be absent;
7. Wood reported the second doubled at its insertion, sending one slip to the radial side of the middle finger, and one to the ulnar side of the index;
8. Wood also found the muscle bipenniform in origin, taking origin from the tendons of the index and middle fingers;
9. A similar division of the orgin was found for the third lumbrical;
10. The third has been found bifurcated at insertion-one-half going to the ulnar side of the middle, and the other to the radial side of the ring finger by Wood, Froment and by Macalister;
11. The entire third lumbrical has been seen going to the ulnar side of the middle finger. Mr Wood found this in a subject in which the fourth was absent;
12. The fourth has been noticed as absent by Sömmerring, Meckel, Weber-Hildebrandt, Wood and by Macalister;
13. All the lumbricals were found missing in one subject by Macalister. The fourth has been found bifurcated, supplying the ulnar side of the ring, and the radial side of the little finger (Wood);
14. The fourth was found giving off the perforated flexor for the little finger in the case of absence of this tendon from the flexor sublimis;
15. The first and fourth have been found springing from special tendons of profundus;
16. The third and fourth may bifurcate at their insertion according to Kelly, Gegenbaur, and Macalister;
17. Five lumbricals have been reported by Walther, by Petsche, and by Böhmer. In one of these cases, two lumbricals were for the middle, two were for the ring, and none were for the little finger; in another, two were for the middle, and the rest were normal. The varieties of the lumbricals have been investigated by Froment who found variations in 45% of subjects, Wood finds them to vary in 18 to 19% (19/102), and Macalister found 50 in 400 subjects (12.5%);
18. The lumbrical to the fourth finger was found by Gruber to be a bundle of fibers from the third interosseous A lumbrical muscle was found passing through Guyon's canal. Guyon's canal is formed by a fascial thickening, which covers the space containing the ulnar neurovascular bundle, attached to the pisiform and to hook of the hamate bones. It is also known as the superficial part of the flexor retinaculum and it is covered by the palmaris brevis muscle.

References

Basu, S.S. and S. Hazary. (1960) Variations of the lumbrical muscles of the hand. Anat. Rec. 136:501-503.

Butler, Jr.,B. and E.C. Bigley, Jr. (1971) Aberrant index (first) lumbrical tendinous origin associated with carpal-tunnel syndrome. J. Bone Joint Surg. (A) 53:160-162.

Durksen, F. (1978) Anomalous lumbrical muscles in the hand: a case report. J. Hand Surg. 3:550-551.

Goldberg, S. (1970) The origin of the lumbrical muscles in the hand of a South African native. Hand. 2:168-171.

Gruber, W. (1887) Eine Reihe neuer Varitäten des Musculus lumbricalis 1 manus. Arch. Path. Anat. Physiol. Klin. Med. 110:555-559.

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

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.

Metha, H.J. and W.U. Gardner. (1961) A study of lumbrical muscles in the human hand. Am. J. Anat. 109:227-238.

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

Nicola, B. (1906) Sur les insertions distales des musculi lumbricales dans la main de l'homme. Arch. Ital. Biol. 45:282-283.

Reinhardt, E. (1902) Über den Ansatz der Musculi lumbricales an der hand des menschen. Anat. Anz. 20:129-134.

Russel, K.F. and S. Sunderland. (1937-38) Abnormalities of the lumbrical muscles of the hand. J. Anat. 72:306307.

Schmidt, H.M., Heinrichs, H.-J. and D. Reissig. (1963) Die Mn. lumbricales an der Hand des Menschen, ihre Variations in Ursprung und Ansatz. Anat. Anz. 113:414-449.

Still, Jr., J.M. and H.E. Kleinert. (1973) Anomalous muscles of nerve entrapment in the wrist and hand. J. Plastic Reconstructive Surgery. 52:394-400.

Wood, J. (1866) Variations in human myology observed during the winter session of 1865-66 at King's College, London. Proc. Roy. Soc. Lond. B. 15:229-244.

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.

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