Musculoskeletal ImagingCarpal coalition
a fusion of carpal bones that may be part of a generalized
congenital malformation, such as
acrocephalosyndactyly, Ellis - van Creveld syndrome (
chondroectodermal dysplasia) or
Turners syndrome, or may occur as an isolated abnormality.
In cases of isolated carpal coalition, the lunate and triquetrum bones are most commonly affected, often with widening of the scapholunate interosseous space (Fig.1). Nearly any combination of fused bones, including multiple fusions, may be found, however. Radiographically, identification of isolated carpal coalition may be difficult owing to the incompleteness of fusion and the need for multiple radiographic projections.
Carpal fusion occurring as part of a congenital syndrome may be massive and may also be associated with tarsal coalition. Such cases result from failure of segmentation of the developing cartilaginous canals, and lack of joint formation. Radiographs reveal trabeculae that can be traced continuously from one bone to the next. Usually the alterations of congenital carpal coalition can be differentiated from the acquired ankylosis that may accompany other disorders, such as infection, juvenile chronic arthritis and trauma.
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PA radiograph of the wrist demonstrates coalition of the lunate and triquetrum. Also noted are a hypoplastic scaphoid and overgrowth of the capitate and hamate.
(Courtesy of Thomas Broderick, MD, Orange, CA)
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Carpal coalition, Fig.1 | |