Pitfalls and limits of locking plates.

The use of locking plates relies on novel mechanical and biological concepts: the bone healing is endochondral because of the elasticity of the constructs. Preoperative planning is required to determine the fracture reduction strategy and select the implants. The type of plate and the type of screws and their position determine the mechanical properties of the construct. Failure of locking plate fixation is a new phenomenon that differs from conventional plate fixation. These are brought on by inadequate planning, which is made worse when minimally invasive surgery is performed. Often, the fracture is not reduced correctly (leading to malunion), the implant length is incorrect, or the screw type, number, location and implantation sequence are inappropriate. Together these can result in an overly rigid construct with poor healing and implant failure or the opposite, an overly flexible construct that can compromise healing. The return to weight bearing after fracture fixation must be adapted to the type of fracture and construct. While locking plates provide better bone purchase, especially in osteoporotic bone, "en bloc" pulling out of the implant is possible. Delayed fractures at the end of the plates are also possible but can be avoided by making the correct biomechanical choices during fixation. For epiphyseal fractures, there are risks of cut-out and impaction of locking screws in cancellous bone related to the fracture pathology. In the long-term, locking plates can be difficult to remove; however, specialized instrumentation can make this easier.