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Syndactyly and split hand. Supplement
Syndaetyly and Split Hand. Supplement. Takayuki Miura
SYNDACTYLY A N D SPLIT H A N D . SUPPLEMENT. TAKAYUKI MIURA, Nagoya, Japan. SUMMARY In a series of studies of clinical and radiologicai features of hand anomalies, the author has recently encountered cases which may be explained by reference to the relationship between syndactyly and split hand. These cases suggested how the typical split hand is formed prenatally, and it is concluded that the typical split hand should not be classed as "Arrest of Development of Parts" due to embryonal failures. INTRODUCTION Keenly interested in the clinical similarity of cases otherwise distinguishable by appearances such as typical split hand and webbing of normal fingers, the author proposed the hypothesis that some such cases may embryologically be closely related with each other, while others seemingly similar to each other may result from different embryological failures. The author has studied these points of malformation of the hand, and already reported a few conclusions (Miura, 1976, a). (1) many split hands have clinical features representing the union of the digital rays, (2) the webbing of the normal fingers and the typical split hand have many clinical similarities, (3) patients with syndactyly in one hand and splitting in the other or in the foot are not rare, (4) the study of abnormal development of the apical ectodermal ridge offers a reasonable explanation of these findings. (O'Rahilly 1956, Yasuda 1975) Since the publication of the above conclusions, the author has received criticism that, although there are indeed some similarities in radiological findings in these cases, the anatomical findings in them are not clear enough. In this connection, the author has recently obtained data from a few additional cases proving the split hand to result from digital ray union. Two cases of central ray polydactyly suggesting a close relationship between the typical split hand, the webbing of normal fingers and central ray polydactylies. CLINICAL STUDIES In the present study, the author made arteriograms of three cases that are intermediate between syndactyly and split hand. Each of them had three arteries to the ring finger. These findings suggested to us that the ring finger represents the union of two digital rays (Fig. 1). In two cases of split hand, the extensor digitorum communis tendon of the middle finger runs to the head of the third metacarpal and turns to the top of the head. It appears to terminate there, but further observation reveals that its main fibres run to the dorsum of the proximal phalanges of the ring finger, with some branching out to the radial side (Fig. 2). Namely, the extensor digitorum communis tendon of the middle finger may be separated into two parts, and main fibres may be fused to the one of ulnar digit (ring finger). Takayuki Miura, M.D., Branch Hospital, Nagoya University School of Medicine, 2-12 1 Higashisakura, Higashiku, Nagoya, Japan. The H a n ~ V o l . 10
No. I
1978
99
Syndactyly and Split Hand. Supplement. Takayuki Miura
Fig. I. three eases with arteriograms below, each showing three arteries to the ring finger.
i
~
~
~
I I
! I
Fig. 2. Extensor digitorum communis to the middle finger divides into two and some fibres join the ring finger. Fig. 3. Broad perforated distal phalanx suggests it has been formed from the fusion of the distal phalanx of the thumb and the index fingers phalanges.
The author previously presented the hypothesis (Miura 1976, b) that the triphalangeal thumb in a complicated split hand may be a fusion of the thumb and the index finger, on the grounds of two epiphyses on the first metacarpal at both distal and proximal ends, and of the form of the triangular wedged middle phalanges. The broad perforated distal phalanges of the thumb in similar cases of split hand suggest that the distal phalanges of the thumb and index finger are fused (Fig. 3). 100
The Hand--Vol. 10
No. 1
1978
Syndactyly and Split Hand. Supplement. Takayuki Miura
Fig. 4. Case 1. Left middle finger has separated into two components and each component has lused to an adjacent finger. Right hand is a typical split hand.
Fig. 5. Case 2. Left middle finger has separated into two components. The ulnar half has fused to the ring finger. The right hand is a typical split hand.
The Hand--VoL 10
No. 1
1978
101
Syndactyly and Split Hand. Supplement. Takayuki Miura
In this series, thirty cases of syndactyly between the middle and ring fingers, and eleven cases of split hand are examined radiographicaUy. Brachymesophalangy 5 is found in 56.7% of syndactylies between the middle and ring fingers, and in 58.8% of split hands. These high incidences of brachymesophalangies 5 and 2, and similarity in the incidence between syndactylies and split hands provide some interesting information as to embryological abnormality. Central ray polydactyly is rare, but some cases of hidden polydactyly are found in syndactylies. TABLE l
Brachymesophalangy 5 No. of affected cases
Brachymesophalangy 2
Frequency
No. of affected cases
Frequency
Syndactyly middle, ring
17 cases
56.7%
7 cases
23.3%
Syndactyly others
16 cases
84.2%
5 cases
21.7%
Split hand
10 cases
58.8%
2 cases
18.2%
Case 1. The middle finger of the left hand in this case was separated into two components at the metacarpo-phalangeal joint, and each component was fused to the adjacent finger, i.e. the index finger or the ring finger. Most fibres of the extensor digitorum communis tendon of the middle finger run to the ulnar finger, with some branching at the proximal phalanges of the radial finger. The third metacarpal had two heads at the distal end, and joined with two phalanges. There is little doubt that the right hand in this case is one of the typical split hands (Fig. 4). Case 2. The middle finger of the left hand was separated into two components, too. The ulnar finger was fused to the ring finger, and the radial finger notch was partially independent. There is little doubt that the right hand is one of the typical split hands (Fig. 5). These findings in the two cases presented above provide good evidence of how the split hand is formed. DISCUSSION
When the author proposed the hypothesis that the typical split hand may result from syndactyly, only a few radiological features and clinical similarities were available as evidence. Now, additional cases are available, providing a clue to these complicated relations between syndactyly and the split hand. The author showed in the previous cases that the fingers on either side of the cleft one had three common digital arteries, and that the extensor digitorum communis tendon of the middle finger ran to the ring finger. Another case is shown in this series. The two cases of central polydactyly, with the other hand in each case being the typical split hand, clearly show how the typical split hand is formed prenatally. 102
The Hand--Vol. 10
No. 1
1978
Syndactyly and Split Hand. Supplement. Takayuki Miura
The author proposes from the clinical and radiological features in these cases that abnormalities of the embryo at the stage when the digits are separated or when the interdigital space is formed, probably a failure in the separation and disappearance of the apical ectodermal ridge, are the grounds of how the split hand, syndactyly and central polydactyly are formed. In other words, if the failure in the separation of digits is limited, the middle finger m a y develop into two parts, each being fused with the adjacent finger, and hyper-regression of the embryonic central interdigital tissue may form and lead to the split hand. These facts are clear in the four radiological features of the two cases. Thus, it m a y be concluded that the typical split hand should not be classified as "Arrest of Development of Parts" (Swanson 1976) on the grounds of embryological failure. The author would like to propose another category that is "Failure of the Interdigital Space" or "Failure in the Separation of Digits", and this includes the webbing of normal fingers, central polydactyly and typical split hands. REFERENCES
MIURA, T. (1976) a. Syndactyly and Split Hand. The Hand, 8:125 130. MIURA, T. (1976) b. Triphalangeal Thumb. Plastic and Reconstructive Surgery, 58: 58%594. O'RAHILLY, R., GARDNER, E. & GRAY, D. J. (1956) The ectodermal thickening and ridge in the limbs of staged human embryos. Journal of Embryology and Experimental Morphology, 4: 254-264. SWANSON, A. B. (1976) A Classification for Congenital Limb Malformation. The Journal of Hand Surgery, 1: 8-22. YASUDA, M. (1975) Pathogenesis of preaxial polydactyly of the hand in human embryos. Journal of Embryology and Experimental Morphology, 33:745 756.
The Hand--Vol. 10
No. 1
1978
103
Syndactyly and Split Hand. Supplement. Takayuki Miura
In this series, thirty cases of syndactyly between the middle and ring fingers, and eleven cases of split hand are examined radiographicaUy. Brachymesophalangy 5 is found in 56.7% of syndactylies between the middle and ring fingers, and in 58.8% of split hands. These high incidences of brachymesophalangies 5 and 2, and similarity in the incidence between syndactylies and split hands provide some interesting information as to embryological abnormality. Central ray polydactyly is rare, but some cases of hidden polydactyly are found in syndactylies. TABLE l
Brachymesophalangy 5 No. of affected cases
Brachymesophalangy 2
Frequency
No. of affected cases
Frequency
Syndactyly middle, ring
17 cases
56.7%
7 cases
23.3%
Syndactyly others
16 cases
84.2%
5 cases
21.7%
Split hand
10 cases
58.8%
2 cases
18.2%
Case 1. The middle finger of the left hand in this case was separated into two components at the metacarpo-phalangeal joint, and each component was fused to the adjacent finger, i.e. the index finger or the ring finger. Most fibres of the extensor digitorum communis tendon of the middle finger run to the ulnar finger, with some branching at the proximal phalanges of the radial finger. The third metacarpal had two heads at the distal end, and joined with two phalanges. There is little doubt that the right hand in this case is one of the typical split hands (Fig. 4). Case 2. The middle finger of the left hand was separated into two components, too. The ulnar finger was fused to the ring finger, and the radial finger notch was partially independent. There is little doubt that the right hand is one of the typical split hands (Fig. 5). These findings in the two cases presented above provide good evidence of how the split hand is formed. DISCUSSION
When the author proposed the hypothesis that the typical split hand may result from syndactyly, only a few radiological features and clinical similarities were available as evidence. Now, additional cases are available, providing a clue to these complicated relations between syndactyly and the split hand. The author showed in the previous cases that the fingers on either side of the cleft one had three common digital arteries, and that the extensor digitorum communis tendon of the middle finger ran to the ring finger. Another case is shown in this series. The two cases of central polydactyly, with the other hand in each case being the typical split hand, clearly show how the typical split hand is formed prenatally. 102
The Hand--Vol. 10
No. 1
1978
SYNDACTYLY A N D SPLIT H A N D . SUPPLEMENT. TAKAYUKI MIURA, Nagoya, Japan. SUMMARY In a series of studies of clinical and radiologicai features of hand anomalies, the author has recently encountered cases which may be explained by reference to the relationship between syndactyly and split hand. These cases suggested how the typical split hand is formed prenatally, and it is concluded that the typical split hand should not be classed as "Arrest of Development of Parts" due to embryonal failures. INTRODUCTION Keenly interested in the clinical similarity of cases otherwise distinguishable by appearances such as typical split hand and webbing of normal fingers, the author proposed the hypothesis that some such cases may embryologically be closely related with each other, while others seemingly similar to each other may result from different embryological failures. The author has studied these points of malformation of the hand, and already reported a few conclusions (Miura, 1976, a). (1) many split hands have clinical features representing the union of the digital rays, (2) the webbing of the normal fingers and the typical split hand have many clinical similarities, (3) patients with syndactyly in one hand and splitting in the other or in the foot are not rare, (4) the study of abnormal development of the apical ectodermal ridge offers a reasonable explanation of these findings. (O'Rahilly 1956, Yasuda 1975) Since the publication of the above conclusions, the author has received criticism that, although there are indeed some similarities in radiological findings in these cases, the anatomical findings in them are not clear enough. In this connection, the author has recently obtained data from a few additional cases proving the split hand to result from digital ray union. Two cases of central ray polydactyly suggesting a close relationship between the typical split hand, the webbing of normal fingers and central ray polydactylies. CLINICAL STUDIES In the present study, the author made arteriograms of three cases that are intermediate between syndactyly and split hand. Each of them had three arteries to the ring finger. These findings suggested to us that the ring finger represents the union of two digital rays (Fig. 1). In two cases of split hand, the extensor digitorum communis tendon of the middle finger runs to the head of the third metacarpal and turns to the top of the head. It appears to terminate there, but further observation reveals that its main fibres run to the dorsum of the proximal phalanges of the ring finger, with some branching out to the radial side (Fig. 2). Namely, the extensor digitorum communis tendon of the middle finger may be separated into two parts, and main fibres may be fused to the one of ulnar digit (ring finger). Takayuki Miura, M.D., Branch Hospital, Nagoya University School of Medicine, 2-12 1 Higashisakura, Higashiku, Nagoya, Japan. The H a n ~ V o l . 10
No. I
1978
99
Syndactyly and Split Hand. Supplement. Takayuki Miura
Fig. I. three eases with arteriograms below, each showing three arteries to the ring finger.
i
~
~
~
I I
! I
Fig. 2. Extensor digitorum communis to the middle finger divides into two and some fibres join the ring finger. Fig. 3. Broad perforated distal phalanx suggests it has been formed from the fusion of the distal phalanx of the thumb and the index fingers phalanges.
The author previously presented the hypothesis (Miura 1976, b) that the triphalangeal thumb in a complicated split hand may be a fusion of the thumb and the index finger, on the grounds of two epiphyses on the first metacarpal at both distal and proximal ends, and of the form of the triangular wedged middle phalanges. The broad perforated distal phalanges of the thumb in similar cases of split hand suggest that the distal phalanges of the thumb and index finger are fused (Fig. 3). 100
The Hand--Vol. 10
No. 1
1978
Syndactyly and Split Hand. Supplement. Takayuki Miura
Fig. 4. Case 1. Left middle finger has separated into two components and each component has lused to an adjacent finger. Right hand is a typical split hand.
Fig. 5. Case 2. Left middle finger has separated into two components. The ulnar half has fused to the ring finger. The right hand is a typical split hand.
The Hand--VoL 10
No. 1
1978
101
Syndactyly and Split Hand. Supplement. Takayuki Miura
In this series, thirty cases of syndactyly between the middle and ring fingers, and eleven cases of split hand are examined radiographicaUy. Brachymesophalangy 5 is found in 56.7% of syndactylies between the middle and ring fingers, and in 58.8% of split hands. These high incidences of brachymesophalangies 5 and 2, and similarity in the incidence between syndactylies and split hands provide some interesting information as to embryological abnormality. Central ray polydactyly is rare, but some cases of hidden polydactyly are found in syndactylies. TABLE l
Brachymesophalangy 5 No. of affected cases
Brachymesophalangy 2
Frequency
No. of affected cases
Frequency
Syndactyly middle, ring
17 cases
56.7%
7 cases
23.3%
Syndactyly others
16 cases
84.2%
5 cases
21.7%
Split hand
10 cases
58.8%
2 cases
18.2%
Case 1. The middle finger of the left hand in this case was separated into two components at the metacarpo-phalangeal joint, and each component was fused to the adjacent finger, i.e. the index finger or the ring finger. Most fibres of the extensor digitorum communis tendon of the middle finger run to the ulnar finger, with some branching at the proximal phalanges of the radial finger. The third metacarpal had two heads at the distal end, and joined with two phalanges. There is little doubt that the right hand in this case is one of the typical split hands (Fig. 4). Case 2. The middle finger of the left hand was separated into two components, too. The ulnar finger was fused to the ring finger, and the radial finger notch was partially independent. There is little doubt that the right hand is one of the typical split hands (Fig. 5). These findings in the two cases presented above provide good evidence of how the split hand is formed. DISCUSSION
When the author proposed the hypothesis that the typical split hand may result from syndactyly, only a few radiological features and clinical similarities were available as evidence. Now, additional cases are available, providing a clue to these complicated relations between syndactyly and the split hand. The author showed in the previous cases that the fingers on either side of the cleft one had three common digital arteries, and that the extensor digitorum communis tendon of the middle finger ran to the ring finger. Another case is shown in this series. The two cases of central polydactyly, with the other hand in each case being the typical split hand, clearly show how the typical split hand is formed prenatally. 102
The Hand--Vol. 10
No. 1
1978
Syndactyly and Split Hand. Supplement. Takayuki Miura
The author proposes from the clinical and radiological features in these cases that abnormalities of the embryo at the stage when the digits are separated or when the interdigital space is formed, probably a failure in the separation and disappearance of the apical ectodermal ridge, are the grounds of how the split hand, syndactyly and central polydactyly are formed. In other words, if the failure in the separation of digits is limited, the middle finger m a y develop into two parts, each being fused with the adjacent finger, and hyper-regression of the embryonic central interdigital tissue may form and lead to the split hand. These facts are clear in the four radiological features of the two cases. Thus, it m a y be concluded that the typical split hand should not be classified as "Arrest of Development of Parts" (Swanson 1976) on the grounds of embryological failure. The author would like to propose another category that is "Failure of the Interdigital Space" or "Failure in the Separation of Digits", and this includes the webbing of normal fingers, central polydactyly and typical split hands. REFERENCES
MIURA, T. (1976) a. Syndactyly and Split Hand. The Hand, 8:125 130. MIURA, T. (1976) b. Triphalangeal Thumb. Plastic and Reconstructive Surgery, 58: 58%594. O'RAHILLY, R., GARDNER, E. & GRAY, D. J. (1956) The ectodermal thickening and ridge in the limbs of staged human embryos. Journal of Embryology and Experimental Morphology, 4: 254-264. SWANSON, A. B. (1976) A Classification for Congenital Limb Malformation. The Journal of Hand Surgery, 1: 8-22. YASUDA, M. (1975) Pathogenesis of preaxial polydactyly of the hand in human embryos. Journal of Embryology and Experimental Morphology, 33:745 756.
The Hand--Vol. 10
No. 1
1978
103
Syndactyly and Split Hand. Supplement. Takayuki Miura
In this series, thirty cases of syndactyly between the middle and ring fingers, and eleven cases of split hand are examined radiographicaUy. Brachymesophalangy 5 is found in 56.7% of syndactylies between the middle and ring fingers, and in 58.8% of split hands. These high incidences of brachymesophalangies 5 and 2, and similarity in the incidence between syndactylies and split hands provide some interesting information as to embryological abnormality. Central ray polydactyly is rare, but some cases of hidden polydactyly are found in syndactylies. TABLE l
Brachymesophalangy 5 No. of affected cases
Brachymesophalangy 2
Frequency
No. of affected cases
Frequency
Syndactyly middle, ring
17 cases
56.7%
7 cases
23.3%
Syndactyly others
16 cases
84.2%
5 cases
21.7%
Split hand
10 cases
58.8%
2 cases
18.2%
Case 1. The middle finger of the left hand in this case was separated into two components at the metacarpo-phalangeal joint, and each component was fused to the adjacent finger, i.e. the index finger or the ring finger. Most fibres of the extensor digitorum communis tendon of the middle finger run to the ulnar finger, with some branching at the proximal phalanges of the radial finger. The third metacarpal had two heads at the distal end, and joined with two phalanges. There is little doubt that the right hand in this case is one of the typical split hands (Fig. 4). Case 2. The middle finger of the left hand was separated into two components, too. The ulnar finger was fused to the ring finger, and the radial finger notch was partially independent. There is little doubt that the right hand is one of the typical split hands (Fig. 5). These findings in the two cases presented above provide good evidence of how the split hand is formed. DISCUSSION
When the author proposed the hypothesis that the typical split hand may result from syndactyly, only a few radiological features and clinical similarities were available as evidence. Now, additional cases are available, providing a clue to these complicated relations between syndactyly and the split hand. The author showed in the previous cases that the fingers on either side of the cleft one had three common digital arteries, and that the extensor digitorum communis tendon of the middle finger ran to the ring finger. Another case is shown in this series. The two cases of central polydactyly, with the other hand in each case being the typical split hand, clearly show how the typical split hand is formed prenatally. 102
The Hand--Vol. 10
No. 1
1978