CONGENITAL ANOMALY OF HAND: " MIRROR HAND " By M. MUKERJI, F.R.C.S. Presidency General Hospital, Calcutta Case Report.--S. B., aged 4 months, was born with eight fingers and no thumb on the left hand and the left forearm was broader than the right. The left upper arm and shoulder were normal. The left elbow had restriction of movement. Extension was full, but flexion was restricted to 3o both in active and passive movements. The left wrist and the fingers were flexed. The child could not extend the wrist, and extension of the fingers was incomplete. The metacarpo-phalangeal joints could not be extended, although the interphalangeal joints could. FIG. I FIG. 2 Photographs of the hand from volar and dorsal aspects. The left hand developed in two halves in two planes at right angles to each other (Figs. I and 2); the half in the same plane as the forearm had three well-formed fingers representing the little, ring, and middle fingers of the hand. The fourth finger from the medial side was bifurcated and probably represented the index fingers of both palms (halves). The other half of the palm was at right angles to the former half, that is, almost in the plane of the thumb if it developed normally. This latter half had three fingers which represented the little, ring, and middle fingers from lateral to medial side, proving that the bifurcated fourth finger represented the index fingers of both halves. The two little fingers were at the two extreme borders of the mirror-shaped hand. These latter fingers flexed and extended at right angles to the other group of fingers simulating to some extent the functions of the absent thumb. X-rays of the hand and forearm show extraordinary developments and confirm the clinical findings. There are seven metacarpals with the two smallest ones representing the two little fingers at the extreme medial and lateral borders of the hand. The fourth metacarpal from both sides has the bifurcated first 222
CONGENITAL ANOMALY OF HAND: " MIRROR HAND" 223 phalanx representing the bifurcated index fingers. All the fingers show three phalanges disproving the presence of the thumb completely. The carpals are not ossified. The forearm shows the presence of two ulnae and the elbow joint is formed with two olecranon processes. The lower end of the humerus does not show any FIG. 3 X-ray photograph of left hand and forearm. FIG. 4 X-ray photograph of right hand and forearm. abnormality or difference from the normal side (normal side X-ray included), probably because the condyles and epicondyles have not yet ossified (Figs. 3 and 4)- Muscles of the Left Forearm and Hand.--The left forearm showed an unusually strong response in all flexor group of muscles. The extensor group showed a very doubtful response. The small muscles of the hand were normal (see muscle chart). Family History.--This child was the third issue of the parents ; the first child was born in I946 and died two days after a forceps delivery; he had no
224 BRITISH JOURNAL OF PLASTIC SURGERY abnormality. The second child was born in 1948 perfectly normal and is healthy. There was no history of any abnormality of fingers, hands, or forearms in any FIG. 5 Fig. 5---Photograph of left hand of father. Fig. 6.--X-ray photograph of father's humerus and elbow. member of the parents' families in the last five generations. The past history of the father gave something of interest. In 1949, four years before the birth of this child, he had an open fracture of the humerus with involvement of the radial nerve and the elbow joint. As a result he had a stiff elbow and dropped wrist exactly simulating his child's elbow and hand. An X-ray photograph of the father's arm shows a malunited fracture of the humerus with ankylosis of the elbow joint (Figs. 5 and 6). Muscle Chart.--Both the father and the child were tested for the activity of the different groups of muscles of the upper extremity and the result is shown below :- FATHER Position of the Part-- Left upper extremity is held in Same. extension at the elbow and flexion at the wrist. Arm Muscles-- Normal response to faradic current. Forearm Muscles-- Flexor muscles were normal. Extensor muscles had no response excepting mild galvanic response in extensor digitorum. Small Muscles of the Hand-- Normal response. CHILD FIG. 6 All muscles had normal response except biceps which had mild response to faradism. Flexor muscles were stronger than usual. Doubtful response. Normal response.
CONGENITAL ANOMALY OF HAND : " MIRROR HAND" 225 Development of Hand with Comparative Anatomy.--In the fourth to fifth week of intrauterine life the upper limb buds develop as slight ridges on each side of the trunk. Prolongations of mesenchyme and myotomes of fourth cervical to second thoracic segments extend into each bud. The axial part of the mesenchyme condenses and forms the cartilaginous skeleton ; the bone forms by ossification of these cartilages. The musculature of the limb is developed in situ from the mesoderm which surrounds the developing skeletal elements. The lateral epicondyle of the humerus, the radius, and the thumb lie in the pre-axial border of the upper limb and the medial epicondyle, the ulna, and the other FIG. 7 FIG. 8 Normal forearms and hands. " Mirror " hands. four fingers lie in the post-axial border. These groups of bones are probably interdependent in their development. The arm portion is separated first by a constriction and then by the hand. Differentiation of digits occurs before differentiation of the remaining parts of the forearm. As the bones differentiate, the muscle groups in relation to the bone become separated and start growing. All these differentiations are complete by about the sixth week of foetal life ; therefore any deformity such as deficiency of a bone or excess of any parts must take place before the sixth week. The Abnormalities in the Present Case and their Explanation.--The child has two ulna: in the forearm with no radius ; she has eight fingers in two mirror hands with no thumb ; and, further, she has stronger flexor muscles with probably no extensor muscles. It seems that the mechanism of this abnormal formation may be as follows : the portion of the extremity beyond the elbow was becoming duplicated in a mirror image form, but two pre-axial parts, that is, two radii and thumbs, disappeared, and the two ulna: with eight fingers remained behind (Figs. 7 and 8).
226 BRITISH JOURNAL OF PLASTIC SURGERY Twinning or Reduplieation.--Twinning or reduplication is very common among lower animals, for example, a crab may develop four claws or a lizard two tails. Stockhard and others have shown that a reduplication of the embryonic parts may be brought about experimentally by a temporary arrest of the embryonic development at the critical growth period. When a growing apical bud is arrested in development by pinching off or other method, dichotomous growth occurs and as a result two adjacent axillary buds quiescent during the supremacy of the apical bud begin to develop twin branches. Similarly, Stockhard has produced a reduplication of parts and marked degree of twinning in trout embryo by arresting the development at a critical period of growth. Arndt and Schuttz claim that minor stimuli cause irritation and result in overgrowth or division, while major stimuli cause inhibition and result in stunting, webbing, or absence, etc. The above can explain reduplication but cannot explain the absence of radii or thumbs. Atavism.raThe same cannot be explained by atavism, although polydactylism is explained by the theory of throwback to the multi-rayed fins of fish. But in this case there is no real polydactylism but absence of two thumbs from a reduplicated hand. There is no animal which does not develop radius and thumb in the normal course. In some mammals which have lost the function of pronation and supination of hand, the ulna has become rudimentary and has fused with the radius which expands at its upper end for weight-bearing. In elephants alone the ulna enlarges for weight-bearing and the radius reduces to a minor bone. Thumb.--The fingers are very varied in distribution amongst the animals. Reptiles and amphibians have five fingers but the fingers differ as the animals ascend up the order according to Darwin's theory. The carnivora and the hoofed animals walk on their metacarpal heads or terminal phalanges of the medial four fingers (post-axial), the thumb having been lost or reduced to a dew-claw. But these animals have a normal radius and ulna in the forearm, so atavism cannot explain the defects of either the forearm or hand. Heredity.--Last, but not the least, is the hereditary influence. There is no such history in the child's family for the last five generations, but the defect in the father's left upper extremity which was involved long before the conception of this child makes one pause and think whether any cause and effect relationship can be drawn from it. The father had a stiff elbow and a dropped wrist, that is, the pre-axial portion of the extremity was not working. Such tendencies are never known to be implanted on to the child through germplasm, and the next issue of the couple will probably add to its proof. Therefore this anomalous hand is another example of the freak of nature which goes by the name of teratology. Proposed Line of Treatment.--When the child is big enough to stand operative interferences, the plan of treatment should be as follows :-- I. Amputation of the half of the bifurcated index finger and the whole of the contiguous finger on its radial side. This will make the web for the thumb.
CONGENITAL ANOMALY OF HAND: " MIRROR HAND" 227 2. The thumb should then be constructed by fusion of the last two fingers of the palm at right angles to the plane of the forearm, that is, the two later almost-fingers. 3. Support of the wrist in dorsiflexion at this time, and transplantation of some fexor muscles to the dorsum when the child is about 4 or 5 years old, or fixation of the wrist in dorsiflexion when the child is I2 to 14 years old. 4. Excision of one or two heads of the ulna for increasing the range of movement in the elbow joint when the child is about I2 years old.