Symphalangism

Last revised by Dr Daniel J Bell on 04 Aug 2022

Symphalangism refers to ankylosis or synostosis of the interphalangeal joints (i.e. fusion of the phalanges) in either the toes or the fingers. Less commonly, the metacarpophalangeal joints may be affected.

One study reports symphalangism of the fifth toe in ~55% (range 40-75%) of the population. It less commonly affects the fourth (~5%) and third toes (~1%) in descending incidence 1.

Symphalangism may also be associated with many conditions including 3:

Stiffness, lack of volar skin fold and reduced range of motion may be present 4. More often, it is an incidental finding on radiographs.

Symphalangism is most commonly seen as an isolated anatomical variant as a fusion of the middle and distal phalanges in the 5th toe 1.

Symphalangism was coined by Howard Cushing in 1916 2.  

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Cases and figures

  • Case 1: third, fourth and fifth toe symphalangism
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  • Case 2: fifth toe symphalangism with fracture
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  • Case 3: 1st-4th PIP fusion
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  • Case 4: little toe symphalangism with fracture
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  • Case 5: little toe pedal biphalangism with fracture
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