Congenital clasped thumb or thumb-clutched (or clasped) hand, is characterized by marked flexion of the first metacarpo-phalangeal joint and adduction into the palm.
The syndrome has been classified into following subtypes
- Group I – Deficient extension only
- Group II – Deficient extension combined with flexion contracture
- Group III – Hypoplasia of the thumb associated with deficiencies of muscles and tendons
- Group IV – The few cases not falling in the first three groups.
Congenital clasped thumb is rare anomaly. Involvement is almost always bilateral.
Males are more commonly affected than females and familial incidence has been observed
Extensor pollicis brevis is hypoplastic or absent. Sometimes the extensor pollicis longus muscle may also be involved.
The tendons of these thumb extensors are not completely absent.
They are attenuated into thin thread-like tendinous structures which narrow proximally and terminate into fibrofatty tissue and there is no real muscle attached to them. There is no fixed contracture and there are no other finger or hand anomalies.
There is flexion contracture of the thumb.
There are significant flexion contracture of the other digits and, occasionally, mild flexion contracture of elbows and knees.
In Group III
The involvement is more severe and diffuse.
The thumb is small, the first metacarpal and its phalanges are hypoplastic, and the metacarpophalangeal joint is unstable.
There is partial or complete absence of the extensor tendons of the thumb, thenar muscles, and abductor pollicis longus.This group probably represents a mild form of longitudinal deficiency of the radial ray.
Cases usually represent varying degrees of polydactyly with associated musculotendinous weakness.
It must be noted that the first three to four months of infancy, grasp reflex is normal-the thumb is flexed across the palm and the fingers are flexed over the clutched thumb. Spontaneously and upon stimulation, the infant will actively extend his fingers and thumb.This normal grasp posture should be distinguished from congenital clasped thumb.
The treatment depends on the type of clasped thumb.
Group I thumbs usually respond to conservative nonsurgical measures.
The thumbs are splinted into extension and abduction. The splints should be well molded to keep the metacarpophalangeal and interphalangeal joints of the thumbs in complete extension and the thumb metacarpal in abduction.
In Group II or in late cases of Group I will require surgical correction by Z plasty and skin graft.
In Group III cases the metacarpophalangeal joint is unstable and it is treated by arthrodesis in the patient over 12 years of age and chondrodesis in the younger child. Tendon transfers are required to provide thumb extension and abduction.
Group IV cases involve the redisual clutched thumb after the supernumerary thumb has been excised. Treatment consist of prolonged retention of the remaining thumb in extension-abduction in a plaster of Paris cast or plastic splint.
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