The aim of this study was to measure the magnitude and direction of forces and torque within osteotomized scaphoids within cadaveric wrists during grasping movement of the hand. The mechanical contributions of clinically relevant individual wrist-crossing tendon groups were investigated. Wrists of 8 forearms were immobilized in the sagittal, transverse and coronal plane on a fixation device with unhindered axial gliding. The scaphoid was osteotomized and the fragments stabilized using an interlocking nail. The nail served as a sensor for measurement of inter-fragmentary forces orthogonal and torque around the sensor axis. Thus, torque and cantilever forces were measured which originated between the fragments through co-contraction through the activity of wrist-crossing tendons. Grasping movement of the hand induced a mean maximum torque of 0.038 ± 0.051Nm and a force of 4.01 ± 1.71N on the scaphoid. The isolated activation of thumb tendons resulted in a torque of 9.9E^-3  ± 7.7E^-3 Nm and a force of 1.42 ± 0.49N. Despite immobilization of the wrist, grasping movement of the hand caused substantial forces and torque within the osteotomized scaphoid bone in varying directions and severity among different specimens. These factors may contribute to the development of nonunions and malunions in unstable scaphoid fractures through interfragmentary micromotion. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.