Smith's fracture generally occurs after falling on the palm of the hand

Orthopedic trauma surgeons often encounter Smith's fracture in patients who report that they have fallen on the palms of their hands. The aim of this study was to clarify the pathogenesis of Smith's fracture in basic clinical aspects. First, a survey was conducted for investigating the mechanism of injury and arm position at the time of injury among patients with Smith's fractures who consulted at our outpatient clinic. Second, we created three-dimensional finite element models (FEMs) to predict the influence of arm position on the type of injury resulting from a fall. These predictions were then used in ten freshly frozen cadavers to provide experimental proof of Smith's fractures resulting from the impact on the palmar side. Twenty-six patients (5 males and 21 females) with Smith's fractures were enrolled in this study. Injury resulting from a fall on the palm of the hand, the dorsum, or ulno-dorsum of the hand, and fisting handle was observed in 16 cases (61%), 3 cases (12%), and 1 case (4%), respectively. Six patients were uncertain of their arm position at the time of injury. FEM analysis showed that Smith's fractures occurred when the angle between the long axis of the forearm and the ground was 30°-45° in the sagittal plane and 75°-90° in the coronal plane. Smith's fractures occurred in 7 of 10 wrists in the experimental study, whereas no Colles' fractures were observed. This study demonstrated that Smith's fracture results from falling on the palm of the hand. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2435-2441, 2017.