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KEY POINTS
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Key Points

  • Medial deviation of finger at distal interphalangeal joint. Fifth finger most commonly affected.

  • Not an anomaly. Usually due to developmental delay or arrest.

  • Present in 1% of normal individuals, but also found in 60% of newborns with Down syndrome.

  • Associated with many genetic syndromes.

  • A detailed fetal ultrasound evaluation should be performed. If clinodactyly is isolated, karyotype is not indicated. If an additional anomaly is found on a detailed scan, obtain a fetal karyotype.

  • Isolated clinodactyly can be inherited as an autosomal dominant trait.

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CONDITION
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The term clinodactyly derives from the two Greek words—kleinin, meaning “to bend,” and dactylos, which means “finger.” Clinodactyly is a descriptive term that refers to incurving or medial deviation of the finger at the distal interphalangeal joint (Figure 102-1). The fifth finger is most frequently affected. Usually, this is due to wedging of the middle phalanx so that the planes of the proximal and distal ends are not parallel but converge toward the radial side (Birkbeck, 1975). Clinodactyly is frequently accompanied by brachymesophalangy, which means that the middle phalanx of the fifth finger is short and has increased breadth. There have been several attempts to provide an objective definition of clinodactyly. In one approach, clinodactyly is defined as the relationship between the length of the fifth middle phalanx to the length of the fourth middle phalanx (Birkbeck, 1975). Other authors have used an angle of greater than 8 degrees between the long axis of the distal phalanx and the middle phalanx (Birkbeck, 1975). Yet other groups use a more stringent definition of a distal phalanx deviation of at least 15 degrees (Skvarilova and Smahel, 1984).

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Figure 102-1

Photograph of a child’s hand demonstrating medial incurving of the fifth finger consistent with a clinical diagnosis of clinodactyly.

Graphic Jump Location
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Clinodactyly may be isolated or part of a syndrome. It may be a sporadic developmental event or it may be familial (Poznanski et al., 1969). Approximately 60% of newborns with Down syndrome have bilateral fifth finger clinodactyly (Hall, 1970). The association between clinodactyly and Down syndrome has been known for more than 100 years (see Chapter 131). In 1896, Smith published the first X-ray illustrating fifth finger clinodactyly in a patient with Down syndrome (Smith, 1896).

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INCIDENCE
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Several large population studies have addressed the incidence of clinodactyly in healthy infants and children. In Czechoslovakia, Skvarilova and Smahel (1984) studied 911 healthy children from Prague, age 6 to 18 years. They defined clinodactyly as the presence of any distal phalanx axis deviation of greater than 15 degrees on clinical examination. Affected children underwent radiography and the hands of their immediate family members were examined. Clinodactyly of the fifth ...

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