Carpal coalition

Last revised by Magdi Mahsoub on 3 Mar 2025

Carpal coalition refers to the abnormal union of two or more carpal bones. It is usually congenital and results from the failure to separate the involved bones during development. The most commonly involved bones are the lunate and triquetrum, although many combinations of united bones have been reported.

Carpal fusion is a misnomer, as the failure of normal segmentation of carpal mesenchyme results in this anomaly 7,8. Carpal coalition is a less contentious term as its definition means a connection between two bones; it says nothing about how they came to be connected 9.

The estimated prevalence is probably <1%, although it has been reported to be as high as ~9.5% 1,2,7,11,14,15. There may be a high prevalence in African Americans or West Africans 1,2,7,11,15.

Carpal coalitions are usually asymptomatic and discovered incidentally 11,12.

As with tarsal coalition, congenital carpal coalition can either be osseous (synostosis), cartilaginous (synchondrosis), or fibrous (syndesmosis) or mixture of types 16. They can often be bilateral 16.

Carpal coalitions can be 11

Almost every combination of carpal coalition have been recorded

Other much less common types include:

  • pisiform-hamate coalition 10

  • capitate-trapezoid coalition 13

Cases and figures

  • Case 1: luno-triquetral coalition
  • Case 2: luno-triquetral coalition
  • Case 3: luno-triquetral coalition
  • Case 4: luno-triquetral coalition
  • Case 5: capitato-trapezoid
  • Case 6: extensive
  • Case 7
  • Case 8: multiple carpal coalitions
  • Case 9: lunotriquetral coalition
  • Case 10: lunotriquetral coalition
  • Case 11: multiple carpal and metacarpal coalition
  • Case 12
  • Case 13: lunotriquetral coalition
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