Biomechanical testing of fracture fixation constructs: variability, validity, and clinical applicability.

Biomechanical testing of fracture fixation implants is crucial in preclinical evaluation and in comparing new devices with standard devices. Many variables must be considered when planning and implementing a biomechanical in vitro experiment. The type of test selected (eg, load-to-failure, stiffness, cyclic fatigue) depends on the research question being asked. For example, cyclic fatigue testing attempts to replicate clinical situations; thus, the load magnitudes and directions and the number of cycles should be decided accordingly. Most important, each bone and region of bone experiences specific in vivo forces based on muscular and other forces. Debate persists regarding whether cadaver or synthetic bone is optimal. The use of either material in biomechanical testing should be carefully considered and justified in the context of the study hypothesis. Appropriate study design is the main factor that affects the clinical applicability of the findings and the accuracy of the conclusions.