The double-arc sign, also known as the McKee double-arc sign, is a radiographic indication of a coronal shear fracture of the distal humerus, which involves the capitellum and extends beyond the lateral trochlear ridge to include a part of the trochlea 1,2.
The double-arc sign is characterized on a lateral radiograph of the elbow by two separately visible arcs representing the displaced capitellum and the trochlea 1,2.
History and etymology
Michael McKee is a Canadian orthopedic surgeon who first published about the double-arc sign in 1996 when he was a Fellow at Massachusetts General Hospital 2.