The subject under discussion here is one of the most frequent and most typical fractures in children. The use of Kirschner pins is not in question, but their number and position is. We present here a biomechanical analysis of how the train force affects the fissure in supracondylar fractures of the humerus with different forms of osteosynthesis using Kirschner pins, and how stable the osteosynthesis is. The experiments were carried out at the Laboratory of Biomechanics in the Institute of Anatomy of the Medical Faculty of Zagreb.