Simulation study on the mechanical mechanism of humeral fracture during throwing.

The purpose of this study was to understand the mechanical mechanisms behind throwing fractures and their relation to bone degeneration. Finite models were built based on three bone degeneration evaluation indexes. All models showed that the crack initiated at the morphological transition junction of the distal 1/3 of the humeral shaft. The initial crack line was lateral to the humerus and extended spirally at 45° with the humerus axis. The fracture torque of healthy humerus was about 63 N·m, with a fracture torque degree of about 12°, both decreasing with increasing bone degeneration.