1. Biomechanics is essential for understanding how fractures occur and how to best treat injuries. The fixation system must be stable and strong enough to allow early mobility before healing is complete. 2. There are four basic forces that act on bones - compression, tension, torsion, and bending. Materials have an elastic range where they return to their original shape and a plastic range where permanent deformation occurs. 3. Implant failure can be biological, due to patient factors, or mechanical, such as screw breakage or plate failure. Characteristics like screw length, diameter, and bone density affect fixation strength.