Cleft hand, also known as lobster-claw hand or split hand,[1] is a rare form of a congenital disorder in which the development of the hand is disturbed. It is a type I failure of formation – longitudinal arrest.[2] The central ray of the hand is affected and usually appears without proximal deficiencies of nerves, vessels, tendons, muscles and bones in contrast to the radial and ulnar deficiencies. The cleft hand appears as a V-shaped cleft situated in the centre of the hand.[3] The digits at the borders of the cleft might be syndactilyzed, and one or more digits can be absent. In most types, the thumb, ring finger and little finger are the less affected parts of the hand.[4] The incidence of cleft hand varies from 1 in 90,000 to 1 in 10,000 births depending on the used classification. Cleft hand can appear unilateral or bilateral,[3] and can appear isolated or associated with a syndrome.
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Literature shows that cleft hand is described centuries ago. The first reference to what might be considered a cleft hand was by Ambroise Paré in 1575. Hartsink (1770) wrote the first report of true cleft hand. In 1896, the first operation of the cleft hand is performed by Doctor Charles N. Dowed of New York City.[1] However, the first certain description of what we know as a cleft hand as we know it today is described in the closure 19th century.[1]
Historically, a U-type cleft hand was also known as atypical cleft hand. The classification in which typical and atypical cleft hand are described was mostly used for clinical aspects and is shown in table 1. However, nowadays, this “atypical cleft hand” is referred to as symbrachydactyly and is not a subtype of cleft hand.
Table 1: Comparison of clinical features of typical cleft hand and atypical cleft hand (symbrachydactyly)
| Typical cleft hand | Atypical cleft hand (symbrachydactyly) |
|---|---|
| Typical hand was manifest in the complete or incomplete absence of the middle finger[5] | Atypical hand had a more severe manifestation in which there was varying absence of the central index, middle and ring finger rays[5] |
| “V”-shaped cleft[3] | “U”-shaped cleft[3] |
| One to four limbs involved[3] | One limb involved (no feet)[3] |
| Higher incidence[1] | Lower incidence[1] |
| Autosomal dominant[3] | Sporadic[3] |
| Suppression progresses in a radial direction so that in the monodactylous form the most ulnar finger is preserved[3] | Suppression progresses in a more ulnar direction, therefore in the monodactylous form mostly the thumb is the last remaining digit[3] |
Cleft hand can be present as an isolated difference. But the exact incidence so far is unknown.
Cleft hand is associated with number of syndromes, see table 2.
Table 2: Cleft hand related syndromes
| Syndrome |
|---|
| Ectrodactyly–ectodermal dysplasia–cleft syndrome |
| Split-Hand-Foot Malformation Syndrome |
| Silver-Russell syndrome |
| Cornelia de Lange syndrome |
| Acrorenal syndrome |
| Focal dermal hypoplasia |
| Ectrodactyly and cleft palate syndrome |
| Ectrodactyly/mandibulofacial dysostosis |
| Ectrodactyly and macular dystrophy |
The etiology of cleft hand is thought to be a result of a wedge-shaped defect of de apical ectoderm of the limb bud (AER: apical ectodermal ridge).[3] Polydactyly, syndactyly and cleft hand can occur within the same hand, therefore some investigators suggest that these entities occur from the same machanism.[3] This mechanism is not yet defined.
The cause of cleft hand lies, for what is known, partly in genetics. The inheritance of cleft hand is autosomal dominant and has a variable penetrance of 70%.[3] Cleft hand can be a spontaneous mutation during pregnancy (de novo mutation). The exact chromosomal defect in isolated cleft hand is not yet defined. However, the genetic causes of cleft hand related to syndromes have more clarity.[6] The identified mutation for SHSF syndrome (split-hand/split-foot syndrome) is 7q21-q22. A mutation in chromosome 3q27 (p63 gene) is found in families affected by SHSF syndrome and in families affected by EEC syndrome (ectrodactyly–ectodermal dysplasia–cleft syndrome).[6] The p63 gene plays a critical role in the development of the apical ectodermal ridge (AER), this was found in mutant mice with dactylaplasia.[3]
Some studies[6][7][8] have postulated that polydactyly, syndactyly and cleft hand have the same teratogenic mechanism. In vivo tests showed that limb anomalies were found alone or in combination with cleft hand when they were given Myleran. These anomalies take place in humans around day 41 of gestation.[6]
There are several classifications for cleft hand, but the most used classification is described by Manske and Halikis[1] see table 3. This classification is based on the first web space. The first web space is the space between the thumb and the index.
Table 3: Classification for cleft hand described by Manske and Halikis
| Type | Description[9][10] | Characteristics[10] |
|---|---|---|
| I | Normal web | Thumb web space not narrowed |
| IIA | Mildly narrowed web | Thumb web space mildly narrowed |
| IIB | Severely narrowed web | Thumb web space severely narrowed |
| III | Syndactylized web | Thumb and index rays syndactylized, web space obliterated |
| IV | Merged web | Index ray suppressed, thumb web space is merged with the cleft |
| V | Absent web | Thumb elements suppressed, ulnar rays remain, thumb web space no longer present |
The treatment of cleft hand is usually invasive and can differ each time because of the heterogeneity of the condition. The function of a cleft hand is mostly not restricted, but yet, improving the function is one of the goals when the thumb or first webspace is absent.
The social and stigmatising aspects of a cleft hand require more attention. A hand is a part of the body which is usually shown during communication. When this hand is obvious different and deformed, stigmatisation or rejection can occur. Sometimes, in families with cleft hand with good function, operation for cosmetic aspects are considered as marginal[3] and choose not to be operated.
Surgical treatment of the cleft hand is based on several indications[3]:
Improving function
Esthetical aspects
The timing of surgical interventions is debatable. Parents have to decide about their child in a very vulnerable time of their parenthood. Indication for early treatment are the progressive deformity’s, such as syndactyly between index and thumb or transverse bones between the digital rays.[3] Other surgical interventions are less urgent and can wait for 1 or 2 years.
When surgery is indicated, the choice of treatment is based on the classification. Table 4 shows the treatment of cleft hand divided into the classification of Manske and Halikis. Techniques described by Ueba, Miura and Komada and the procedure of Snow-Littler are guidelines, since clinical and anatomical presentation within the types differ, the actual treatment is based on the individual abnormality.
Table 4: Treatment based on the classification of Manske and Halikis
| Type | Treatment |
|---|---|
| I/IIA | Reconstruction of the transverse metacarpal ligament[11] |
| IIB/III | Transposition of the index metacarpal with reconstruction of the thumb webspace[11] |
| IV | Mobility and/or position of the thumb of ulnar digit to promote pinch and grasp[1] |
| V | There is no cleft or web space and the thumb is very deficient. This hand requires consideration of creating a radial digit[1] |
The goal of this procedure is to create a wide first web space and to minimise the cleft in the hand. The index digit will be transferred to the ulnar side of the cleft. Simultaneously occurs a correction of index malrotation and deviation.[3] To minimise the cleft, it’s necessary to fixate the metacarpals together which used to border the cleft. Through repositioning flaps, the wound can be closed.
Ueba described a less complicated surgery.[3] Transverse flaps are used to resurface the palm, the dorsal side of de transposed digit and the ulnar part of the first web space. A tendon graft is used to connect the common extensor tendons of the border digits of the cleft to prevent digital separation during extension. The closure is simpler, but has cosmetic disadvantage because of the switch between palmar and dorsal skin.
The release of the first webspace has the same principle as the Snow-Littler procedure. The difference is the closure of the first webspace, this is done by simple closure or closure with Z-plasties.[3]