Locked Plating: Biomechanics and Biology and Locked Plating: Clinical Indications

Abstract

Summary: “Bridging plate osteosynthesis” using a locked plate is the technique of spanning the fracture site with an internal fixator without exposing the fracture site, and was developed to preserve fragment vascular supply. This technique requires stabilization of the bone proximal and distal to the fracture site to achieve bone healing without direct manipulation of fracture fragments, and is ideal for comminuted and compley diaphyseal and metadiaphyseal fracture patterns, particularly in osteoporotic bone. Locked plating systems provide both angular and axial construct stability through a threaded interface between the screw heads and the plate body, which directly fixes the screw to pressing the plate directly to a bony surface is obviated, preserving blood supply and reducing the need for plate contouring. Furthermore, the angular and axial stability of locked plates minimizes the risk of secondary loss of reduction. Primary loss of reduction is minimized, as exact plate contouring is not required. Bicortical locked screws were superior to unicortical locked screws in all modes of loading because of the increased working length, or amount of bone purchase present. Locked plating allows for stable fracture fixation without the need for plate contouring or direct contact with bone. To maintain osseous blood supply, the plate is placed in an extraperiosteal position, and will likely have no direct contact with bone. Initial clinical data demonstrate excellent union rates, low rates of fixation failure, and few associated complications with the use of locking plates for internal fixation of fractures, particularly periarticular fractures. Locking plate technology will undoubtedly proliferate for fractures in other anatomic locations. Hybrid plates offering the versatility of choosing either a locked or unlocked screw will probably enjoy widespread use. The clinical success of these implants is probably the result of the improved biologic environment provided by minimally invasive plate insertion as well as the stable mechanical environment. As with all new technology, caution is warranted. Because these implants are used for difficult fractures, complications both old (e.g., malalignment, infection) and new (e.g., difficult hardware removal, incorrectly placed screws, pullout) will occur. When such plates are inserted percutaneously, malalignment is common. Further clinical and biomechanical research on locking plate technology is needed to define its place fully alongside existing technology in orthopaedic trauma.