Bilateral bipartite trapezoid: a rare anatomical variant

From left to right: lateral radiograph showing the bipartite trapezoid (black arrows); sagittal CT confirmed the cleft with sclerotic margins (white arrows); axial proton density fat saturated MRI showed oedema within the fibrocartilaginous cleft (white arrows); coronal proton density fat saturated MRI showed small cystic change in the trapezoid (white arrows). The trapezoid is an irregular, boot-shaped bone, lying in the distal carpal row.1 Encircled by carpal bones and the base of the second metacarpal, and with strong intercarpal ligaments binding it in place, the trapezoid is the least commonly fractured carpal bone in isolation, with few published cases in the literature.2–4 Carpal bone bipartition is an anatomical variant that occurs due to the formation of two cartilaginous centres rather than one, or non-union of two ossification centres.5 The most common bipartite carpal is the scaphoid.5 To date, there exists a single case report describing unilateral right bipartite trapezoid in a 17-year-old man identified on radiographs and CT following fall onto the outstretched hand.6 No imaging of the contralateral wrist was undertaken to confirm the presence of bilateral bipartite trapezoids. 5 Burnett SE, Stojanowski CM, Mahakkanukrauh P. Six new examples of the bipartite trapezoid bone: morphology, significant population variation, and an examination of pre-existing criteria to identify bipartition of individual carpal bones.