Ectrodactyly is a genetic disorder of skeletal anomaly resulting in the complete or partial absence of fingers or toes due to longitudinal deficiency.
Webbing between fingers or toes (syndactyly) may occur giving hands and/or feet a claw-like appearance.
The condition has a widely ranging severity and there are combinations of deformities that appear. The malformation may occur alone, or it may occur as a component of a syndrome.
Ectrodactyly is also called split hand-split foot malformation, cleft hand, or lobster claw hand, Karsch-Neugebauer syndrome.
Split hand-split foot malformation affects males and females equally. Frequency is estimated at one out of 18,000 newborns.
In contrast to radial and ulnar deficiency, the central deficiency of the hand in ectrodactyly is without proximal deficiencies of nerves, vessels, tendons, muscles and bones.
Following photographs are of a patient with ectrodactyly of both hand and feet.
Hands
Feet
Hands and Feet together
Genetics and Pathophysiology
The split-hand deformity can run in families as an autosomal dominant trait or as X-linked recessive trait in other families. It is known to occur due to random mutation.
The most common mode of inheritance is autosomal dominant with reduced penetrance, while autosomal recessive and X-linked forms are less common.
Often, in a new mutation a single limb is affected whereas in an inherited condition, often, all the limbs are affected but this is not sacrosanct.
- SHFM1 (chromosome 7q21)
- SHFM2 (chromosome Xq26)
- SHFM3 (chromosome 10q24)
- SHFM4 (chromosome 3q27)
- SHFM5 (chromosome 2q31)
Ectrodactyly is also seen with many syndromes which include-
- Ectrodactyly-Ectodermal Dysplasia-Clefting syndrome
- Ectrodactyly-Cleft Palate syndrome
- Ectrodactyly-Ectodermal Dysplasia-Macular Dystrophy syndrome
- Ectrodactyly-Fibular Aplasia/Hypoplasia syndrome
- Ectrodactyly-Polydactyly
A form of ectrodactyly associated with deafness has also been described.
The pathophysiology of cleft hand is thought to be a result of a wedge-shaped defect of the apical ectoderm of the limb bud. As poldactyly, syndactyly and cleft hand may occur together, it is suggested that these entities may arise from the same mechanism which is still not clear.
Classification of Ectrodactyly
The classification for cleft hand has been described by Manske and Halikis.
Type I – Normal Web
Thumb webspace is not narrowed
Type II – Narrow Web
- IIA-MildlyNarrowWeb
- Thumb webspace mildly narrowed
- IIB – Severely narrowed web
- Thumb webspace severely narrowed
Type III – Syndactylized web
There is syndactyly between thumb and index finger. The webspace is obliterated.
Type IV- Merged web
The index ray suppressed and web of thumb is merged with the cleft.
V- Absent web
Elements of thumb are suppressed. Ulnar rays are present but webspace of thumb is no longer present.
Clinical Presentation
Typical cases of split-hand deformity usually appear in two forms.
In the lobster claw type there is usually an absence of the third digit. Instead, there is a cone-shaped cleft that tapers in toward the wrist and divides the hand into two parts, divding the hand which resembles a lobster claw.
The fingers on on either side of the cleft are often joined or webbed together, partially or completely. Often the lobster claw is bilateral.
In the second variety, there is the presence of only the fifth digit and there is no cleft. The condition has variable severity, even in the same family.
Apart from from deformity and its effect on daily routine and morale, the individuals with split-hand deformity usually have normal life spans and intelligence.
Functions of the cleft hand are mostly not restricted.
Diagnosis
The deformity can be identified at birth. X-rays would provide additional information.
Treatment of Ectrodactyly
The treatment is often surgical and the choice of procedure depends on the clinical presentation, severity and the varied forms of the condition.
Progressive deformities, such as syndactyly between index and thumb or transverse bones between the digital rays require early treatment. Other interventions are considered at the age of 1-2 years.
Indications for Treatment are
- Absent thumb
- A syndactyly causing deformity as in between thumb and index finger
- Transverse bones (this will progress the deformity; growth of these bones will widen the cleft)
- Narrowed first webspace
- Aesthetics
- Improving function
The choice of procedure depends on the individual presentation. Based on the classification, the following treatments can be considered.
- I/IIA- Reconstruction of the transverse metacarpal ligament
- IIB/III- Transposition of the index metacarpal and reconstruction of the thumb webspace
- IV – Mobilization of thumb or ulnar digit for pinch and grasp functions
- V – Requires creation of a thumb
Prosthetics can be considered where surgery cannot be done.
