Flexor Digitorum Profundus

This muscle has a radial origin in about 84% of cases studied (Mori).The various ways the deep and superficial flexors may be united are discussed under m. flexor digitorum superficialis (sublimis). In addition, a connection with flexor digitorum superficialis and or flexor pollicis longus is frequent, generally in the form of a slip passing to the index finger tendon of the deep flexor. The number of bellies to the muscle may be increased. The origin of the belly to the index finger may not be limited to the radius but may reach the interosseus membrane.

Macalister reported the variations in flexor digitorum profundus as follows:

  1. Cleft, the flexor indicis profundus being separate (Wood); 
  2. An origin from the radius along the entire border of flexor pollicis (Kelly);
  3. A coronoid fasciculus of origin with the coronoid head of sublimis (Wood);
  4. In one subject a separate muscle arose from the coronoid process, in the same situation as the last, and received fibers from the medial part of the front of the radius. It passed beneath the annular ligament, and divided into two-one to join the tendon of flexor pollicis longus, and one to the tendon of the index perforans (Wood);
  5. Some of the fibers to the index finger arose from the radius (Wood);
  6. Macalister has seen a detached muscular slip of the profundus becoming tendinous, and joining that of the sublimis, or the index, in the palm, as described by Mr. Wood);
  7. Mr. Wood has seen the fourth lumbrical arising from a special tendon of this muscle;
  8. Sömmerring found a similar slip which expanded on the synovial sheath of the tendons, giving origin to the first lumbrical;
  9. A distinct pyriform muscle, arising from the coronoid process, constitutes the accessorius ad flexorem profundus of Gantzer. This may form a common coronoid origin for the flexor sublimis and profundus, or a special one for the latter. It has been found joining the perforating tendon of the index finger (six times of seventy-two subjects, Wood), or the perforating tendon of the middle (eight out of seventy-two, Wood), or that of the ring finger alone (Turner), or those of the ring and little (one out of thirty-six, Wood), or that of the little finger alone (Turner), or those of the index or ring fingers, or the index and little. Macalister has seen all nine varieties just described;
  10. Macalister described a pear-shaped muscle arising from the medial condyle, under the flexor sublimis, which ended in a long tendon, and united with the little finger slip of flexor profundus, opposite the metacarpophalangeal articulations;
  11. Methods of union between this muscle and the flexor pollicis longus are common. Macalister has seen a tendon joining the indicial part of profundus with the pollicis, or another muscular slip;
  12. Macalister reports a slip from the ulnar side of flexor profundus running to join the little finger tendon of flexor digitorum sublimis (superficialis);
  13. The tendon has been seen divided into five slips, two of which united to form the tendon for the ring finger;
  14. A special head from the medial condyle (Theile);
  15. An origin from the radius has been seen by Theile, Hallett, Henle, and by Macalister;
  16. In one subject the palmaris longus arose from it (described by Fleischmann).

The separation of the index finger tendon from the others is a distinctly human characteristic, correlated with the specialization of the index finger. The degree of the muscles freedom varies. It may be quite independent, forming a flexor indicis profundus. The radial origin may extend a considerable distance on the bone alongside the long flexor of the thumb. A tendon to the middle finger may be absent.

A muscular slip (accessorius ad flexorem digitorum profundus)arising from the coronoid process and ending by a long tendon on one or another (usually the index or middle) of the tendons of the muscle has been reported in about 20% of bodies. Mori reported 40% in his subjects. Flexor digitorum profundus (Fdp) may receive a muscular slip from the medial epicondyle of the humerus (1:205 arms, Mori), from flexor pollicis longus 12.5%, and Fdp may be fused with flexor digitorum superficialis in 11% of 205 arms according to Mori.

Syn.: m. Flexor digitorum perforans.

References

Adachi, B. (1909) Beiträge zur Anatomie der Japaner. XII. Die Statistik der Muskelvarietäten. Zeitschr. Morphol. Anthropol. 12:261-312.

Dylersky, I. Contribution to the ontogenesis of the flexor digitorum superficialis and the flexor digitorum profundus in man. Folia Morphol. Praha 15:330-335.

Gantzer, C.F.L. (1813) De Musculorem Varietat. Thesis, J. F. Starkii, Berolini.

Gruber, W. (1875) Ein Fall des Vorkommens des Musculus flexor pollicis longus beim Menschen: als Tensor bursae mucosae tendinum mm. flexorum, oder als Kopf des M. flexor digitorum profundus manus. Arch. Anat. Physiol. Wissen. Med. 1875:211-214.

Gruber, W. (1886) Musculus flexor digitorum profundus mit Mangel einer Sehne zum Mittlefinger. Arch. Path. Anat. Physiol. Klin. Med. 103:472-474.

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

Jarjavay, -. (1857) Un muscle surnuméraire de lavant bras. Bulletins et Mem. de la Société Anatomique de Paris XXXII(4)121-122.

Kaneff, A. (1959) Über eine sehr seltene Kombination von Muskelvarietäten des tiefen Fingerstreckers, M. extensor digitorum profundus. Anat. Anz. 107:424-428.

Linburg, R.M. and B.E. Comstock. Anomalous tendon slips from the flexor pollicis longus to the flexor digitorum profundus. J. Hand Surg. 4:79-83.

Loup, -. Le fléchisseur sublime, dans chaque avant-bras, envoie un faisceau au fléchisseur profond et un autre au long fléchisseur du pouce. Lyon Méd.18:375.

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.

Reid, R.W. and S. Taylor (1879) Anatomical Variations. Reports. St. Thomas's Hospital 9:48.

Testut, L. (1884) Les Anomalies Musculaires chez l'Homme Expliquées par l'Anatomie Comparée. Masson, Paris.

Walsham, W.J. (1880) Anotomical variations: An account of a few of the more interesting abnormalities that have occurred in the dissecting-rooms during the last seven years; with remarks on their morphological significance, and their bearing on the practice of surgery. St. Bartholomews Hospital Reports. 16:69-105.

Wilkinson, J. L. (1953) The insertions of the flexores pollicis longus et digitorum profundus. J. Anat. 87:75-88.

Winkelman, N.Z. (1983) An accessory flexor digitorum profundus indicis. J. Hand Surg. 8:70-71.

Wood, J. (1867) Variations in human myology observed during the winter session of 1866-67 at King's College, London. Proc. Roy. Soc. Lond. B 15:518-546.

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 16:483-525.

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