[Flexion deformities of the thumb: clasped thumb and trigger thumb].

Congenital clasped thumb in palm corresponds to a spectrum of anomalies leading to a loss of thumb extension and abduction. Intrinsic muscles and skin shortening are not infrequent. Conservative orthopedic treatment should be undergone as soon as possible. When this treatment fails, or when patients are seen late, surgical correction has to be customized according to the involved structures. The trigger thumb is 10 times more frequent than the trigger finger. It is bilateral in 30% of the cases. The term "congenital" remains unclear as several investigations on newborns have not evidenced trigger thumb. In children, it is very rare to find a real trigger and presentation consists in a fixed flexion deformity of the interphalangeal joint. Diagnosis is clinical, with a palpable nodule at the level of T1 pulley. Conservative treatment, consisting in a nocturnal splint, is indicated before the age of two years old. After this age, or in case of failure of splinting, surgery will be needed.