Clinodactyly: Definition, Causes, Symptoms, Related Anatomy, Diagnosis and Treatment

It is a congenital angular deformity of the middle phalanx.

It is usually bilateral and involves the little finger, although other digits can also be affected.

Clinodactyly is an autosomal dominant condition and occurs in isolation or in association with other syndromes.

Causes of clinodactyly

Clinodactyly can be congenital or acquired.

Congenital clinodactyly is commonly bilateral and presents sporadically as an autosomal dominant trait, with variable expressiveness and incomplete penetrance.

Acquired clinodactyly is usually secondary to physical or thermal trauma to the physis or phalanx, or due to abnormal scarring.

Clinodactyly is usually an isolated abnormality, although it may be part of a syndrome or a chromosomal abnormality.

There are more than 60 syndromes are associated with clinodactyly, the most common of which is Down syndrome.

Other associated syndromes include Rubinstein-Taybi syndrome, Apert syndrome, and oculodentodigital dysplasia.

Symptoms and related anatomy

The main sign is an abnormal curvature of the finger, which can cause problems in the use of musical instruments, such as the piano.

In most cases, there is little or no functional impairment, and the greatest concern is the unsatisfactory appearance of the affected digit.

The middle phalanx of the little finger is more commonly affected in clinodactyly, with deviation towards the fourth finger, instead of the typical rectangular phalanx shape, the phalanx is trapezoidal or delta, which is generally due to a longitudinal epiphyseal support.

The degree of angulation that constitutes clinodactyly varies from case to case.

The condition has been defined by some as an angulation greater than 8 degrees in the long axis of the finger between the proximal and middle phalanges.

Others consider angulation greater than 10 degrees or greater than or equal to 15 degrees to be abnormal.

One of the several classification systems used for clinodactyly groups it into four types:


A deformity of the middle phalanx with an angulation of 15 to 45 degrees.

Simple complicated

A deformity of the middle phalanx with an angulation of 45 to 60 degrees.


With bone and soft tissue deformities, with an angulation of 15 to 45 degrees.

Complicated complex

With bone and soft tissue deformities, with an angulation of 45 to 60 degrees and associated macrodactyly or polydactyly.


The diagnosis is made based on the examination findings, signs, and positive tests.

The doctor initially performs a physical examination of the affected digit.

The physician should inquire about activities of daily living and perform a range of motion test to determine if the condition is affecting the patient’s mobility and / or dexterity.

Clinodactyly can also be identified incidentally during the presentation of an unrelated problem.

Radiographs are often needed to confirm the diagnosis, presenting findings as a C-shaped physis, which is indicative of the presence of clinodactyly.

The specific bony abnormality of the middle phalanx can be difficult to discern on plain radiographs.

The clinical deformity can be seen at an early age, but a radiographic diagnosis of clinodactyly cannot be made until the patient is skeletally mature and sufficient ossification of the epiphysis has occurred.

Incidence and related conditions

Clinodactyly has a reported incidence ranging from 1 to 20 percent of the general population.

Incidence rates are significantly higher in individuals with Down syndrome, reported to range from 35 to 79 percent).

The sex distribution for clinodactyly of the little finger is approximately 15 percent for boys and 8 percent for girls.

It is related to some conditions such as:

  • Triphalangeal thumb.
  • Braquidactilia, camptodactilia, polidactilia, sindactilia.
  • Kirner’s deformity.
  • Apert syndrome, Down syndrome, Rubinstein-Taybi syndrome.
  • Camptodactilia.
  • Delta phalanx.
  • Keratosis palmaris and plantaris.
  • Oculodentodigital dysplasia.

Treatment of clinodactyly

Unless clinodactyly is severe, it usually causes minimal functional impairment, especially if it is the little finger that is involved.

For this reason, observation alone is usually sufficient and surgical intervention is reserved only for cases where the deformity interferes with the function of the fingers or for cosmetic purposes.

Surgical options for clinodactyly include closure, opening, and reversal of wedge osteotomies and physiolysis.

Treatment decisions should be based on the underlying pathology, the age of the patient, and other factors.