"type 1: incomplete fibrocartilaginous fusion resembling a pseudoarthrosis"
"type 2: incomplete osseous fusion"
"type 3: complete osseous fusion"
"type 4: complete osseous fusion with other carpal abnormalities"
"The term "coalition" is preferred over "fusion" for congenital coalitions, as during development, the discrete carpal bones form by a process of separation. The lunate and triquetrum do not form and then later fuse; they just never separate or only do so partially (hence incomplete coalitions) 9."
"Congenital lunotriquetral coalition occurs with failure of segmentation of the carpal bones 1. The coalition may be fibrous, cartilaginous or osseous 5, and is commonly bilateral 4."