The biomechanical environment plays a dominant role in the process of fracture repair. Mechanical signals control biological activities at the fracture site, regulate the formation and proliferation of different cell types, and are responsible for the formation of connective tissues and the consolidation of the fractured bone. The mechanobiology at the fracture site can be easily manipulated by the design and configuration of the fracture fixation construct and by the loading of the extremity (weight-bearing prescription). Depending on the choice of fracture fixation, the healing response can be directed towards direct healing or towards indirect healing through callus formation. This manuscript summarizes the evidence from experimental studies and clinical observations on the effect of mechanical manipulation on the healing response. Parameters like fracture gap size, interfragmentary movement, interfragmentary strain, and axial and shear deformation will be explored with respect to their respective effects on fracture repair. Also, the role of externally applied movement on the potential enhancement on the fracture repair process will be explored. Factors like fracture gap size, type and amplitude of the mechanical deformation as well as the loading history and its timing will be discussed.

Purpose of Review Fractures of osteoporotic bone in elderly individuals need special attention. This manuscript reviews the current strategies to provide sufficient fracture fixation stability with a particular focus on fractures that frequently occur in elderly individuals with osteoporosis and require full load-bearing capacity, i.e., pelvis, hip, ankle, and peri-implant fractures. Recent Findings Elderly individuals benefit immensely from immediate mobilization after fracture and thus require stable fracture fixation that allows immediate post-operative weight-bearing. However, osteoporotic bone has decreased holding capacity for metallic implants and is thus associated with a considerable fracture fixation failure rate both short term and long term. Modern implant technologies with dedicated modifications provide sufficient mechanical stability to allow immediate weight-bearing for elderly individuals. Depending on fracture location and fracture severity, various options are available to reinforce or augment standard fracture fixation systems. Summary Correct application of the basic principles of fracture fixation and the use of modern implant technologies enables mechanically stable fracture fixation that allows early weight-bearing and results in timely fracture healing even in patients with osteoporosis.

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