gms | German Medical Science

Objectives/Interrogation: Smith's fractures generally occur when falling on a flexed wrist; however, orthopedic trauma surgeons often encounter distal radius fractures with volar displacement in patients who have allegedly fallen on the palm of their hands. In our survey, 62% of patients were injured on the palm of the hand. However, it is not known the mechanism of Smith's fractures. The aim of this study was to reveal the pathogenesis of Smith's fracture

Methods: The research plans are performed through a step-by-step investigation. First, to predict the type of distal radius fracture with finite element model (FEM). we created a 3D FEM from CT data of the wrist and analysis fracture pattern. Second, to obtain experimental proof of Smith's fracture occurring upon the application of an impact on the palmar side using fresh frozen cadaver. Finally, to predict stress distribution on the distal radius when Smith's fracture occurs.

Results and Conclusions: As the angle between the long axis of the forearm and the ground decreases, the fracture line shifts to the volar side and Smith's fracture was predicted by FME when its angle was small. In cadaver study, Smith-type fractures were occurred in seven of 10 wrists. In FEA study to predict stress distribution, compression force was applied on the lunate fossa and transmitted to the volar side of wrist. Tensile stress was generated at the dorsal side of the wrist. Therefore, the dorsal cortical bone broke by traction force, and a proximal fragment was dorsally displaced by rotation moment.

In conclusion, Smith's fractures occur not only as a result of falling on the dorsum of the hand during volar flexion, but also as a result of falling on the palm of the hand during dorsal flexion.