Locked Plating in Practice: Indications and Current Concepts

Why use a locked plate? The increasing use of locked plates in fracture care has raised concern that the appropriate usage of these plates is being lost with lack of adherence to some of the basic principles of fracture fixation. The development of locking plate technology has introduced a new and exciting dimension to fracture fixation but they should be applied with specific intent and indications; as such their role is continuously being redefined. The creation of a construct where a fixed angle relationship is created at the plate-screw interface allows these devices to be used essentially as internal-external fixator. Fracture fixation therefore does not rely on the frictional forces between the undersurface of the plate and the bone created by screw purchase, as it does with a conventional plate and screw construct, but rather deforming forces are transferred from the bone through the plate as each screw is “locked” into the plate. This eliminates screw toggle and decreases motion at the fracture site. Because of these mechanical advantages, fractures can often be transfixed with less hardware placement and soft tissue dissection especially in the zone of injury. In addition, the periosteal blood supply can be preserved to a greater degree since, unlike conventional plates, compression to bone is not necessary to achieve stability. Locked plates were developed in response to a need to adequately stabilize fractures where there was poor bone quality—mechanically weaker metaphyseal bone or bone effected by osteoporosis, osteomalacia or comminution— where standard bicortical screws were unable to gain sufficient purchase for maintenance of the plate-bone relationship. For example, extra-articular metaphyseal fractures with short peri-articular segments are ideal for lockedangle plating. In some areas, such as the distal femur, angled blade plates and dynamic condylar screws had proven successful, but these devices are not appropriate for all anatomic regions and are not as successful at capturing all necessary segments of the bony injury. Early attempts at increasing fixation of conventional plates to compromised bone included injection of cement into an area where screws were to be placed and placement of a threaded washer/ nut (Schuhli nut) around a conventional screw to provide angular support. The development of the Less Invasive Stabilization System (LISS) by Synthes (Paoli, PA) in 1995 and the Locking Compression Plate (LCP) in 2000 brought the use of locking plate technology into routine fracture care The indications and uses for locking plate technology continue to be defined. One important problem to avoid is the creation of an overstiff construct by placing locked screws when not needed (or more than what is needed). The resultant relative lack of motion at the fracture site can, in some situations, be too stiff to allow fracture healing. This has led some to refer to locking plates as “nonunion generators.” Thus, the indications and correct utilization of locking plates is important to understand so they are not used inappropriately and compromise fracture healing. In addition, newer techniques such as “hybrid” plating (use of both locking and nonlocking screws in a single construct) and far cortical locking (obtaining purchase in far cortex while bypassing proximal cortex) have evolved to combat these problems sometimes seen with locking plates.