Cleft hand, also known as ectrodactyly, central ray deficiency, lobster-claw deformity, pincer-cleft deformity, crab-claw deformity, and split-hand malformation, refers to a rare group of congenital hand abnormalities in which the central bony elements of the hand are missing. These deformities are characterized by a variable expression in a wide range of clinical phenotypes, but generally include a deficiency of the central ray with narrowing or syndactyly of the adjacent digits, creating a cleft in the center of the hand. Cleft hand can result from a spontaneous mutation, autosomal dominant inheritance, an associated condition or possibly from teratogenic chemicals acting on the embryo. This last potential cause has been support by laboratory studies., Cleft hand may lead to significant functional impairments depending on its severity. In cleft hand patients with satisfactory hand functionality and no desire for surgical correction, regular observation may be sufficient; however, surgery is commonly required for functional and/or cosmetic reasons.1-3 Surgical treatment should preferrably be performed at an early age before hand dominance and skilled hand function develops.
Pathophysiology
- The leading theory on the pathophysiology of cleft hand holds that at Carnegie stage 22, there is a wedge-shaped deficiency in the central part of the apical ectodermal ridge due to the loss of function of certain genes expressed in that region. This causes a failure in the normal process of formation of bones and/or interdigital spaces, which leads to cleft hand3,4
- All the abnormalities of cleft hand are believed to represent various degrees of severity of the same anomaly, suggesting the deformity may be due to an intrauterine vascular occlusion or insufficiency5
- The cleft hand deficiency varies from absent long phalanges to absent individual fingers, to monodactyly, or even the absence of all fingers3 Cleft hand has also been categorized as part of the spectrum of symbrachydactyly.
- The depth of the palmar cleft depends upon the remaining metacarpal bones, with a shallow cleft when they are present and a deep cleft when absent3
- Cleft hand can follow an autosomal dominant inheritance pattern, result from a spontaneous mutation, or stem from one of many associated syndromes; inherited forms become more severe with each generation2
- Deletions, inversions, and translocations of gene 7q have also been associated with cleft hand
Related Anatomy
- Apical ectodermal ridge
- Interdigital spaces
- Metacarpals
- Phalanges
- First web space
- Metacarpophalangeal (MP) joints
- Interphalangeal (IP) joints
- Classifying cleft hand is difficult due to its heterogeneity, but one of the more commonly-used classification systems is as follows:1,6
- Type 1 (Typical)
- Typical V-shaped clefting with presence of metacarpals
- Typical crab clawing of the border digits
- Bilateral
- Involves feet
- Associated with other developmental defects
- Familial inheritance is common
- Type 2 (Atypical)
- Also known as symbrachydactyly
- Atypical cleft that is often U- or wide U-shaped
- Unilateral
- Sporadic
- Partial or complete absence of metacarpals
- Hypoplastic thumb and little finger
- Not associated with other syndromic manifestations
- Type 3 (Nil-clefting)
- All digits are absent1
- The Manske and Halikis classification system is also frequently used:
- Type I: Normal web, and thumb space is not narrowed
- Type IIA: Mildly narrowed web, and thumb space is mildly narrowed
- Type IIB: Severely narrowed web and thumb space is severely narrowed
- Type III: Syndactylized web, thumb, and index rays, and the web space is obliterated
- Type IV: Merged web, index ray is suppressed, and thumb web space is merged with the cleft
- Type V: Absent web, thumb elements are suppressed, ulnar rays remain, and thumb web space no longer present6
Incidence and Related Conditions
- The incidence of typical cleft hand is 1 in 90,000-120,000 births and 1 in 150,000-200,000 births for atypical cleft hand7
- Symbrachydactyly
- Ectrodactyly-ectodermal dysplasia-cleft (EEC) syndrome
- Sensorineural hearing loss
- Syndactyly, polydactyly, clinodactyly
- Bony fusion
- Anencephaly
- Cleft lip/cleft palate
- Scoliosis
- Imperforate anus
- Anonychia
- Cataracts
- Deafness
- Hypoplasia or pseudoarthosis of clavicle
- Absent pectoralis major muscle
- Short humerus
- Synostosis of elbow
- Short forearm
- Absent ulna
- Radioulnar synostosis
- Bilateral absence of tibia
- Bilateral dislocation of hip
- Short femur
- Hypoplastic patella
- Clubfoot
- Calcaneovalgus
- Deviated nasal septum
- Congenital ptosis
Differential Diagnosis
- EEC syndrome
- Cornelia de Lange syndrome
- Acrorenal syndrome
