carpal coalition

Carpal coalition refers to failure of separation of two or more carpal bones, and although the most commonly involved bones are the lunate and triquetrum, most combinations of adjacent bones can be found to be coalesced.

Terminology

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

Epidemiology

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

Associations

There are several associated conditions, especially with multiple coalitions:

Pathology

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

Etiology

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.

Types

The two most common types are: