Carpal coalition

Last revised by Dr Daniel J Bell on 04 Aug 2022

Carpal coalition refers to the abnormal union of two or more carpal bones, and is usually congenital, due to failure of separation of 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 it is the failure of normal segmentation of carpal mesenchyme that results in the anomaly 8. Carpal coalition is less contentious as its definition means a connection between two bones, it says nothing about how they came to be connected 9.

The estimated prevalence is ~0.1% in Caucasian Americans and ~1.5% in African Americans, and it tends to affect women more commonly 1,2.

There are several associated conditions, especially with multiple coalitions:

As with tarsal coalition, congenital carpal coalition can either be osseous (synostosis), cartilaginous (synchondrosis), or fibrous (syndesmosis).

Non-syndromic congenital carpal coalition is transmitted via a Mendelian inheritance pattern. Acquired intercarpal fusion can either be a consequence of an inflammatory arthropathy (e.g. rheumatoid arthritis, psoriatic arthritis, reactive arthritis) or injury, or due to intentional surgical arthrodesis.

The two most common types of congenital carpal coalition are:

Less common

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Cases and figures

  • Case 1: luno-triquetral coalition
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  • Case 2: luno-triquetral coalition
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  • Case 3: luno-triquetral coalition
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  • Case 4: luno-triquetral coalition
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  • Case 5: capitato-trapezoid
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  • Case 6: extensive
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  • Case 7
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  • Case 8: multiple carpal coalitions
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