Lunotriquetral coalition

Last revised by Adeniyi Olorunfemi Fagbohun on 6 Jul 2023

A lunotriquetral coalition, also known as lunotriquetral fusion or synostosis, is a type of carpal coalition and represents a congenital lack of separation of the lunate and triquetral bones of the carpus

The term coalition is preferred over fusion for congenital coalitions, as during development the discrete carpal bones form by a process of separation, i.e. the lunate and triquetral do not form and then later fuse, they just never separate or only do so partially (hence incomplete coalitions) 9.

The lunotriquetral coalition is the most common type of carpal coalition with a prevalence of 0.1%. It is more common in females (F:M = 2:1) and African Americans.

The diagnosis can be established by typical findings on imaging.

Whilst osseous coalitions of the lunate and the triquetrum are known to be asymptomatic, fibrocartilaginous lunotriquetral coalitions can present as an uncommon cause of ulnar-sided wrist pain often due to pseudarthrosis or a post-traumatic disruption 3,8.   

  • the coalition may be fibrous, cartilaginous or osseous 5
  • commonly bilateral 4

Carpal coalitions can follow an autosomal dominant route of inheritance

de Villiers classified lunotriquetral coalition into four types 6:

  1. incomplete (or fibrocartilaginous) fusion - resembles a pseudoarthrosis
  2. incomplete osseous fusion 
  3. complete osseous fusion
  4. complete osseous fusion with other carpal abnormalities
  • incomplete or complete fusion of the lunate and triquetrum
  • possibly accompanied by a widened scapholunate interval 4 

A lunotriquetral coalition is most commonly an incidental finding and does not require treatment if not symptomatic. It might occasionally be the cause of chronic wrist pain (especially in types 1 and 2 6) and can be fractured.

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3
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  • Case 4
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  •  Case 5
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  • Case 6
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  • Case 7
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  • Case 8: ultrasound
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  • Case 9
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  • Case 10: with concurrent capito-hamate coalition
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  • Case 11
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  • Case 12
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  • Case 13: bilateral
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  • Case 14
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  • Case 15
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  • Case 16
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