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Congenital triphalangism of the first finger of the hand: causes, symptoms, diagnosis, treatment
Medical expert of the article
Last reviewed: 07.07.2025
Congenital triphalangism of the first finger of the hand is a developmental defect in which the thumb (like the other fingers of the hand) has three phalanges.
ICD-10 code
- Q74.0 Congenital triphalangism of the first finger of the hand.
Symptoms and diagnosis of congenital triphalangism of the first finger of the hand
The main features that allow differentiating various forms of this defect are: longitudinal dimensions of the first metacarpal bone and the location of its epiphyseal growth zone; dimensions and shape of the additional phalanx: longitudinal dimensions of the first ray of the hand: size of the first intermetacarpal space: condition of the thenar muscles, functions of the hand. Based on the combination of these criteria, the following variants of congenital triphalangism of the first finger of the hand are distinguished: simple form (brachymesophalangeal, pseudotriphalangism, dolichophalangeal) and complex (in combination with hypoplasia of the first ray or with radial polydactyly) form.
On X-ray examination, pseudotriphalangism is characterized by the presence of an expanded epiphysis of the distal phalanx of a trapezoid or rectangular shape, imitating an additional phalanx of the first finger. Clinically, ulnar clinodactyly is noted at the level of the interphalangeal joint of the thumb, the function of the hand is preserved. The brachymesophalangeal form is characterized by the presence of an additional phalanx, the size of which is less than or equal to the distal phalanx; its shape, depending on the severity of the defect, can be triangular, trapezoid or rectangular; the size of the first ray of the hand is close to normal or significantly increased. The muscles of the eminence of the thumb are normally developed, but can be hypoplastic. The function of bilateral grip of the hand is preserved or sharply limited. The dolichophalangeal form of congenital triphalangism of the first finger is manifested by an increase in the longitudinal dimensions of the first ray of the hand; the dimensions of the additional phalanx are larger than the dimensions of the distal phalanx (it has a rectangular shape): significant narrowing of the first intermetacarpal space; pronounced hypoplasia of the thenar muscles, the function of bilateral grasp of the hand is absent or sharply limited.
Treatment of congenital triphalangism of the first finger of the hand
The technique of the operation depends on the form of triphalangism, the age of the child, the size of the additional phalanx and the first ray as a whole relative to the age norm, as well as the degree of underdevelopment of the thenar muscles.
If the middle phalanx is triangular in shape in children under 2 years of age, it is removed and reconstruction of the joint's capsular-ligamentous apparatus is performed. In children over 2 years of age, as well as in cases where the additional phalanx is trapezoid or rectangular in shape, the best results are achieved by wedge resection of the phalanx with simultaneous elimination of one of the interphalangeal joints.
In cases of pseudo-triphalangism, corrective osteotomy of the epiphysis of the proximal phalanx of the first finger is performed by wedge resection. In the doli-hophalangeal form, pollicization of the thumb is considered the operation of choice. In the case of a combination of the brachymesophalangeal form of triphalangism and hypoplasia of the first ray, the thumb is abducted into an opposition position with simultaneous resection of one of the interphalangeal joints. In the case of the dolichophalangeal form with hypoplasia of the phalanges of the thumb and preserved opposition, resection of the interphalangeal joint at the level of which the deformation was noted is performed. In the case of hypoplasia of the entire first ray and thenar muscles, pollicization is performed, which (if necessary) is combined with resection of one of the interphalangeal joints or with the elimination of the flexion contracture of the thumb. When triphalangism is combined with radial polydactyly, along with the removal of additional segments, resection of the most hypoplastic interphalangeal joint (in the brachymesophalangeal form) or pollicization surgery (in the dolichophalangeal form) is performed.
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