Cleft hand, also known as lobster-claw hand or split hand, 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. 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. 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. 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, and can appear isolated or associated with a syndrome.

History

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. 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.

Symbrachydactyly

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

Symbrachydactyly

Symbrachydactyly is a congenital abnormality, characterized by limb anomalies consisting of brachydactyly, cutaneous syndactyly and global hypoplasia of the hand or, rarely, foot. In many cases, bones will be missing from the fingers and some fingers may be missing altogether...

 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	Atypical hand had a more severe manifestation in which there was varying absence of the central index, middle and ring finger rays
“V”-shaped cleft	“U”-shaped cleft
One to four limbs involved	One limb involved (no feet)
Higher incidence	Lower incidence
Autosomal dominant	Sporadic
Suppression progresses in a radial direction so that in the monodactylous form the most ulnar finger is preserved	Suppression progresses in a more ulnar direction, therefore in the monodactylous form mostly the thumb is the last remaining digit

Isolated cleft hand

Cleft hand can be present as an isolated difference. But the exact incidence so far is unknown.

Syndromes

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 Cornelia de Lange Syndrome Cornelia de Lange Syndrome often termed as Bushy Syndrome is a genetic disorder that can lead to severe developmental anomalies. It affects the physical and intellectual development of a child. Exact incidence is unknown, but it is estimated at 1 in 10,000 to 30,000.! Appx...
Acrorenal syndrome
Focal dermal hypoplasia Focal dermal hypoplasia Focal dermal hypoplasia is a form of ectodermal dysplasia.It is also known as Goltz-Gorlin syndrome, after Robert Goltz and Robert Gorlin.It has been associated with PORCN, on the X chromosome.-External links:...
Ectrodactyly and cleft palate syndrome
Ectrodactyly/mandibulofacial dysostosis
Ectrodactyly and macular dystrophy

Etiology

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). Polydactyly

Polydactyly

Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....

, syndactyly

Syndactyly

Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...

 and cleft hand can occur within the same hand, therefore some investigators suggest that these entities occur from the same machanism.
This mechanism is not yet defined.

Genetics

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%.
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.
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). The p63 gene plays a critical role in the development of the apical ectodermal ridge (AER), this was found in mutant mice with dactylaplasia.

Embryology

Some studies 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

Gestation

Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

.

Classification

There are several classifications for cleft hand, but the most used classification is described by Manske and Halikis 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	Characteristics
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

Treatment

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 and choose not to be operated.

Indications

Surgical treatment of the cleft hand is based on several indications:

Improving function

• Absent thumb
• Deforming syndactyly (mostly between digits of unequal length like index and thumb)
• Transverse bones (this will progress the deformity, growth of these bones will widen the cleft)
• Narrowed first webspace
• The feet

Esthetical aspects

• Reducing deformity

Timing of surgical interventions

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. Other surgical interventions are less urgent and can wait for 1 or 2 years.

Classification and treatment

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
IIB/III	Transposition of the index metacarpal with reconstruction of the thumb webspace
IV	Mobility and/or position of the thumb of ulnar digit to promote pinch and grasp
V	There is no cleft or web space and the thumb is very deficient. This hand requires consideration of creating a radial digit

Snow-Littler

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. 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

Ueba described a less complicated surgery. 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.

Miura and Komada

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.

See also

• Ectrodactyly–ectodermal dysplasia–cleft syndrome
• Ectrodactyly
  Ectrodactyly
  Ectrodactyly, sometimes referred to as the “Lobster-Claw Syndrome” involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation...
  
  
• Cleft lip and palate
• Facial cleft
  Facial cleft
  A facial cleft is an opening or gap in the face, or a malformation of a part of the face. Facial clefts is a collective term for all sorts of clefts. All structures like bone, soft tissue, skin etc. can be affected. Facial clefts are extremely rare congenital anomalies...