The Zig-Zag Deformity in the Rheumatoid Hand

Abstract

Abstract Ulnar deviation of the fingers in rheumatoid arthritis has been shown to be very frequently associated with radial deviation of the hand. This constitutes a zig-zag deformity and therefore is due either to a loss of stabilising muscle force or to a ligamentous rupture. The stability of the wrist as against radial deviation in pronation is largely due to the power of Extensor Carpi Ulnaris. The position of the tendon of the Extensor Carpi Ulnaris varies between pronation and supination, and the tendon is in close relation to the triangular ligament of the wrist joint. Loss of function or rupture of the Extensor Carpi Ulnaris allows radial deviation of the hand, and in the presence of rheumatoid disease in the metacarpalphalangeal joint, ulnar deviation of the fingers will result.