Incomplete carpal coalition.

Congenital coalition between the lunate and triquetrum is a common anomaly that may have several different radiographic appearances. We report seven patients with partial coalition and rounded radiolucencies in the subarticular region of both bones. The most likely cause of this combination of findings is abnormal differentiation of the joint space and remnants of misplaced synovial tissue that formed during the disorganized process of joint development.