title: Computer simulation of humeral shaft fracture in throwing.
abstract: OBJECTIVE
  Throwing fractures of the humerus are well known, but the exact mechanism of injury is not clear. It has been postulated that these may be stress fractures because the forces have not seemed sufficient to cause acute fractures while throwing.
  
  
  METHODS
  Using finite element analysis, we reproduced fractures of the humerus using 3-dimensional models built from computed tomography images of 5 healthy volunteers. To apply the load during throwing, we assumed that the humeral head was completely fixed, and external rotation torque was applied to the distal end of the humerus until the stress of the bone elements became greater than yield stress. We reproduced the fracture line by removing the bone elements.
  
  
  RESULTS
  The maximum stress concentration was seen in the distal shaft, where a typical spiral fracture was created in all cases. In the humeral models, the torque required to initiate fracture ranged from 51 to 70 Nm. A strong correlation existed between the torque required to initiate fracture and thickness of the humeral cortical bone (R(2) = 0.74).
  
  
  CONCLUSIONS
  These results indicate that thickness of the humerus represents one factor contributing to fractures that occur while throwing.
  
  
  METHODS
  Basic science study.
authors: Department of Orthopaedic Surgery, School of Medicine, Keio University, Shinjuku-ku, Tokyo, Japan.
authors: Kensuke
authors: K
authors: Sakai
authors: Yoshimori
authors: Y
authors: Kiriyama
authors: Hiroo
authors: H
authors: Kimura
authors: Noriaki
authors: N
authors: Nakamichi
authors: Toshiyasu
authors: T
authors: Nakamura
authors: Hiroyasu
authors: H
authors: Ikegami
authors: Hideo
authors: H
authors: Matsumoto
authors: Yoshiaki
authors: Y
authors: Toyama
authors: Takeo
authors: T
authors: Nagura
mesh_terms: D001265:Athletic Injuries / Q000000981:diagnostic imaging / Q000601:surgery; D001696:Biomechanical Phenomena; D003198:Computer Simulation; D020342:Finite Element Analysis; D006801:Humans; D006810:Humeral Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D013314:Stress, Mechanical; D013718:Tensile Strength; D014057:Tomography, X-Ray Computed; D019415:Torque; D055815:Young Adult