Congenital clasped thumb in children

In short: in congenital clasped thumb the thumb stays folded towards the palm and cannot be actively extended at the metacarpophalangeal joint. It is a different condition from trigger thumb: here the problem lies in the extensor apparatus, not in a flexor tendon nodule. Flexible forms often respond to early splinting; rigid or syndrome-associated forms require assessment in a paediatric hand surgery centre.

In short

In the first months of life it is entirely normal for a newborn to keep the thumb inside the palm: a physiological posture that gradually disappears over the first 3-4 months, as the ability to open the hand and grasp develops. Congenital clasped thumb is diagnosed when this posture persists beyond that period and the child cannot actively extend the thumb.

The mechanism is a deficiency of the thumb extensor apparatus — hypoplastic, absent or poorly functioning extensor tendons — sometimes associated with tightness of the skin and tissues of the first web space. The picture may be isolated, often bilateral, or part of broader conditions such as arthrogryposis or syndromes involving several joints.

Symptoms and when to worry

The main sign is a thumb that remains in the palm beyond the first months, with difficulty bringing it out. The key clinical distinction is between:

• a flexible form, in which the thumb can be extended passively without significant resistance, even though the child does not extend it actively;
• a rigid form, in which passive extension is limited by tissue tightness or joint stiffness.

Involvement of other digits or joints, stiffness of elbows, knees or feet, and an overall asymmetric picture all deserve attention: they point towards a broader condition and change the assessment pathway.

Diagnosis and imaging

Diagnosis is clinical. Active and passive extension of the metacarpophalangeal and interphalangeal joints, mobility of the first web space, presence or absence of a nodule at the thumb base — which would instead point to trigger thumb — and overall hand function in grasp are all assessed. Looking for signs in other joints helps recognise syndromic pictures. Imaging is not routine.

Conservative treatment

In flexible forms the first-line treatment is extension splinting, started early and maintained for a prolonged period, combined with passive mobilisation and encouragement of thumb use in play. The earlier it is started, the more favourable the reported results, though with individual variability.

The splint should be made and adjusted with the support of a hand therapist, because a poorly fitted device risks being ineffective or poorly tolerated. The pathway requires continuity and is reviewed periodically, without promising complete recovery in advance.

When surgery is needed

Surgery is indicated in rigid forms, in pictures that do not change with correctly delivered splinting, and where the limitation compromises grasp. Possible procedures include release of the tight first web space tissues, skin coverage with local flaps and tendon transfers to restore extension.

This is specialist paediatric hand surgery: the pathway is directed to a dedicated centre. Dr Priano provides the assessment, the indication and the orthopaedic follow-up, not the performance of this surgery.

Follow-up and recovery

Follow-up accompanies growth: the extension achieved, the stability of the result and above all the spontaneous use of the thumb in activities are checked. In splint-treated children, monitoring continues after the splint is discontinued, because a proportion of cases may lose part of the result. For the general picture of congenital hand differences see also clinodactyly, camptodactyly and syndactyly.