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Journal of the Anatomical Society of India

Syndactyly Associated With Muscular Variations In Palm: A Dissection Study

Author(s): Dahiphale V. P., Diwan C. V.

Vol. 56, No. 1 (2007-01 - 2007-06)

Dahiphale V. P. and Diwan C. V.

S.R.T.R. Medical College,Ambajogai, Maharashtra


During the routine dissection in a male cadaver, syndactyly of third and fourth fingers was seen in right palm. In the radiograph, there was only soft tissue fusion and absence of middle and distal phalanges of the fourth finger. The third finger showed normal phalanges. During dissection flexor digitorum superficialis appeared to be normal having its four tendons for the medial four fingers. The tendon for fourth finger was found to be inserted in the proximal phalanx. Flexor digitorum profundus had only two tendons for second and fifth fingers. The tendons for third and fourth finger were absent. The belly of flexor digitorum profundus muscle was found to split into three delicate muscle bellies, i.e. II, III and IV lumbricals. The first lumbrical arose from radial side of tendon for index finger.

Key words: Syndactyly, third, fourth, fingers, flexor digitorum superficialis, flexor digitorum profundus, tendons, lumbricals.


Syndactyly is the word derived from greek, syn means together and dactyly means fingers or digits. Syndactly is webbing or fusion of two digits (fingers and toes) due to failure of separation during embryological development. Usually between sixth and eighth week of intrauterine life.

As per observation of Temtamy (1966) syndactyly is described as simple or complex. Simple syndactyly means abnormal interconnection formed by skin and fibrous tissue or ligaments. Complex syndactyly has abnormal digit interconnection by bone.

At one point during the early formation of the limbs, we all had syndactyly of the fingers and toes. If the fingers or toes fail to separate syndactyly result.

Cross H.E. et al (1968) has observed some forms of syndactyly are inherited and may run in the family, other forms are sporadic i.e. it can occur with no familial tendency.

Syndactly of IIIrd and IVth fingers is the commonest congenital anomaly of the hand. The fusion of two fingers may be only soft tissue fusion or it may be associated with bony and muscular anomalies.

Case Report

Avariation of flexor digitorum profundus muscle was found on right forearm and palm during the routine dissection which was associated with syndactyly of third and fourth fingers. When radiography was done, it was found that the fourth finger was having only proximal phalanx with the absence of middle and distal phalanges. The third finger showed normal phalanges.

Flexor digitorum superficialis was normal, only the tendon for fourth finger was inserted into the proximal phalanx instead of middle phalanx.

Flexor digitorum profundus muscle appeared to be the having only two tendons for second and fifth fingers with the absence of tendons for third and fourth fingers. The tendons were separated in the forearm. In the palm the remaining belly of muscle divided into three small delicate bellies, these were second, third and fourth lumbricals. The first lumbrical arose from the radial side of tendon for second (index) finger. The lumbricals were inserted into the dorsal digital expansion.

Other hand showed normal pattern of muscle and tendons in the palm.

Fig.1 Photograph of X-ray showing absence of middle and distal phalanges of IVth finger in syndactyly of IIIrd and IVth fingers.

Fig 2: Photograph showing variations in flexor digitorum profunds and lumbricals
1 → Flexor digitorum profunds (FDP) – brown color
2 → Tendons of Flexor digitorum profunds for second and fifth fingers


Syndactyly occurs about 1 in 2200 cases. The male – to – female ratio is 2:1. Cutaneous syndactyly

i.e. simple webbing of the digits is the most common limb anomaly being more frequent in foot than in hand (De Smet L. 1994).

Cutaneous syndactyly results from failure of the webs to degenerate between two or more digits. In some cases there is fusion of the bones (synostosis). Moore suggests that osseous syndactyly occurs when notches between the digital rays fail to develop during the 7th week, as a result separation of digits doesn’t occur. Robinow (1982) has observed that syndactyly is most frequently seen between third and fourth fingers and between second and third toes. It is inherited as a simple dominant or simple recessive trait.

The present case shows cutaneous syndactyly with absence of development of middle and distal phalanges of the fourth finger along with failure of formation of tendons of flexor digitorum profundus for third and fourth fingers.

Failure of formation of middle and distal phalanges in fourth finger leads to abnormal insertion of the tendon of flexor digitorum superficialis is in the proximal phalange instead of in the middle phalanx of fourth finger.

In the development of the hand, Apical Ectodermal Ridge (AER) at the tip of the hand plate and the underlying somatopleuric mesenchyme are the controllers of the development pattern i.e. notch, ray formation and finger separation (Gray).

As per recent edition of Gray’s anatomy the skeletal elements (phalanges) are formed from somatopleuric mesenchyme in the hand plate, but the muscles are of somitic origin, except for connective tissue envelops and tendons which are of somatopleuric origin. The myogenic cells from the somites migrate in the limb, split and develop into various muscles of the arm, forearm and hand dragging their nerve supply along with them from the somites.

This probably explains the absence of tendons of flexor digitorum profundus for third and fourth fingers and phalanges of fourth finger as a result of somatopleuric mesenchymal growth distruption, but the muscles (lumbricals) are formed and have joined dosal digital expansion as they are formed from the myogenic cells of the somites.

Clinical Importance

Syndactyly can prevent the full extension of the involved fingers, decreasing their functionality.


  1. Cross, H. E.; Lerberg, B. B.; Mckusick,V. A.: Type II syndactyly. American Journal of Human Genetics, 1968; 20:268-380.
  2. De Smet, L.; Mulier, T.; Fabry, G.: Syndactyly of the ring and small fingers. Genetic Counsel, 1994; 5: 45-49.
  3. Moore, K. L. and Persaud, T. V. N.: The developing human. Clinical oriented embryology: The limbs. 7th edition: W. B. Sunders Company. Philadelphia, 2003; PP: 417-418.
  4. Robinow, M.; Johnson, G. F.; Broock, G. J.: Syndactyly type V. American Journal of Medical Genetics, 1982; 11: 475-482.
  5. Temtamy, S. A.: Carpenter’s sydrone: Acrocephalopoly syndactyly: An autosomal recessive syndrome. Journal of Pediatrics, 1966; 69: 111.
  6. Willams, P. L.: Gray’s anatomy in development of limb buds. 38th edition, Churchill livingstone, New York, 1999, PP: 288-289
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