Mechanism of Scanhoid Fracture

Chung, Moon Sang; Kim, Hee Joong; Won, Choong Hee; Lee, Myung Chul

Abstract

Elucidation of the mechanism of fracture seems to be important to prevent to it and determin the position on immobilization most conducive to union. The scaphoid is more susceptable to injury than any of other carpal bones due to its position in bridging the proximal and distal raws of carpal bones and the mechnism of fracture has been a subject of considerable controversy. Reviewing 20 cases of scaphoid nonunion, we incidentally had found that 4 patients had the history of striking a punch bag with the heads of the second and third metacarpals (Punching injury), and a review of the literatures failed to find any reports of such an injury as a mechanism of fracture. On a scale, the wrist was subjected to progressive loading via the heads of the second and third metacarpals and lateral roentgenograms of the wrist were obtained at Okg, 20kg and 35kg and we measured the carpal angles. With progressive loading there is a volar flexion of proximal carpal raw and the volar flexion of scaphoid is smaller than that of lunate. We believed that the violent impact applied at the second and third metacarpal heads forced the scaphoid into the position of extreme dorsiflexion as compared with lunate, so compression force is exerted on the dorsal side of scaphoid and tension on volar side leading the fracture of scaphoid. We also recognized that the fracture of the scaphoid could be occurred by the compression and shearing force of capitate and the bending force of volar radiocapitate ligament.