Effect of Various Wrist and Forearm Motions on Distal Radius Forces

Background  Dart throw motions are frequently used during rehabilitation but the ideal orientation of a dart throw motion is unknown. Questions/Purposes  The purpose of this study was to measure the axial force on the distal radius during different dart throw motions with the wrist and forearm in various positions. Our hypothesis was that there would be a significant difference on the axial force between various forearm positions and different dart throw orientations. Methods  Eight fresh frozen cadaver wrists were moved through 10 different orientations of a dart throw motion with the forearm in neutral, in pronation, and during a dynamic forearm rotation motion while the axial force was measured. Results  Significantly smaller axial force occurred with the forearm in pronation than during the dynamic forearm motion. The shorter dart throw motions which were oriented equally toward the flexion/extension and radioulnar deviation axes had significantly smaller distal radius forces than nearly all of the other dart throw motions. Conclusion/Clinical Relevance  Rehabilitation protocols incorporating a dart throw motion may be of benefit after injury or surgery. To minimize the axial force transmitted through a healing distal radius fracture, short dart throw motions, oriented at 45 degrees from the sagittal and coronal planes, with the forearm in pronation, might be preferable for range of motion activities during rehabilitation.