Forearm fractures in adults are treated surgically with a few exceptions. The purpose of the surgery is obtaining anatomic reduction, stabile fixation, and early starting the range of motion. The gold standard for the surgical treatment of these fractures is compression plate-screw fixation. Surgery of the fore-arm fractures may result in non-union due to inadequate mechanics, biology, and occurrence of infection. If the principles are adhered to, expected nonunion cases will be less than 5%. Understanding the mechanics will help the surgeon to diagnose the underlying reason of the non-union. One should apply the correct principles to fix the inappropriate mechanics.