Locking plate technology: current concepts

The management of fractures with traditional plating techniques has undergone a paradigm shift over the past 20 years. For many fractures, anatomic reduction using a dynamic compression plate has been the gold standard. However, minimally invasive approaches combined with biologically friendly internal fixation have become accepted methods of complex fracture treatment. The orthopedic literature has demonstrated advantages when comparing locking plate techniques with traditional compression plating techniques, particularly in fractures about the knee. The advantages of locking plates apply most directly to cases of highly comminuted fractures, unstable metadiaphyseal segments, and osteoporotic fractures. The biomechanical properties of locking plates have distinguished and defined their clinical use compared to traditional plates. A thorough understanding of these properties will assist the orthopedic surgeon in choosing the appropriate construct when faced with a difficult fracture. Compression plating requires absolute stability for bone healing. In contrast, locking plates function as "internal fixators" with multiple anchor points. This type of fixed-angle device converts axial loads across the bone to compressive forces across fracture sites, minimizing gap length and strain. The strain theory demonstrates that anatomic reduction is not required for bone healing, and that tolerable strain (2%-10%) can promote secondary bone healing. Callus formation is further promoted when biologically friendly surgical approaches are combined with locking plate "internal fixators". In contrast, conventional plates function by creating an environment where primary bone healing occurs. This plate provides "absolute rigidity" and requires anatomic reduction fixed in compression. Primary bone healing occurs in this manner. In highly comminuted, segmentally deficient, or porotic bone, bone quality is poor and "absolute rigidity" does not exist. Furthermore, soft-tissue stripping adds a biologic insult to the poor bone quality. These disadvantages may lead to poor outcomes such as nonunion, implant failure, malunion, or even infection. These disadvantages remain theoretical, as no prospective studies clearly demonstrate a difference between plating methods in difficult metadiaphyseal or osteoporotic fractures. However, the overwhelming biomechanical evidence has led to a more biologically friendly approach to these fractures. The indications for use of locking plates are evolving. The literature demonstrates low rates of nonunion and overall complication rates with locking plates in difficult metaphyseal and diaphyseal fractures. Anatomic reduction of the articular surface remains paramount. Hybrid techniques that combine the benefits of compression plate fixation with the biological and biomechanical advantages of locking plates are the most likely end result of current locking plate applications.