Klinik für Traumaand Sportmedizin, Wilhelminspital Wien, Austria.
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Abstract
The basic principles of an internal fixation procedure using a conventional plate and screw system (compression method) are direct, anatomical reduction and stable internal fixation of the fracture. Wide exposure of the bone is usually necessary to gain access to and provide good visibility of the fracture zone to allow reduction and plate fixation to be performed. This procedure requires pre-contouring of the plate to match the anatomy of the bone. The screws are tightened to fix the plate onto the bone, which then compresses the plate onto the bone. The actual stability results from the friction between the plate and the bone. Anatomical reduction of the fracture was the goal of conventional plating technique, but over time a technique for bridging plate osteosynthesis has been developed for multifragmentary shaft fractures that, thanks to a reduction of vascular damage to the bone, permits healing with callus formation, as seen after locked nailing. Since the damage to the soft tissues and the blood supply is less extensive, more rapid fracture healing can be achieved. The newly developed, so-called locked internal fixators (e.g.PC-Fix and Less Invasive Stabilization System (LISS)), consist of plate and screw systems where the screws are locked in the plate. This locking minimizes the compressive forces exerted by the plate on the bone. This method of screw-plate fixation means that the plate does not need to touch the bone at all, which is of particular advantage in so-called Minimal Invasive Percutaneous Osteosynthesis (MIPO). Precise anatomical contouring of a plate is no longer necessary thanks to these new screws and because the plate does not need to be pressed on to the bone to achieve stability. This prevents primary dislocation of the fracture caused by inexact contouring of a plate. The LISS plates are precontoured to match the average anatomical form of the relevant site and, therefore, do not have to be further adapted intraoperatively. The development of the locked internal fixator method has been based on scientific insights into bone biology especially with reference to its blood supply. The basic locked internal fixation technique aims at flexible elastic fixation to initiate spontaneous healing, including its induction of callus formation. This technology supports what is currently known as MIPO. The development of the Locking Compression Plate (LCP) has only been possible based on the experience gained with the PC-Fix and LISS. With reference to the mechanical, biomechanical and clinical results, the new AO LCP with combination holes can be used, depending on the fracture situation, as a compression plate, a locked internal fixator, or as an internal fixation system combining both techniques. The LCP with combination holes can also be used, depending on the fracture situation, in either a conventional technique (compression principle), bridging technique (internal fixator principle), or a combination technique (compression and bridging principles). A combination of both screw types offers the possibility to achieve a synergy of both internal fixation, methods. If the LCP is applied as a compression plate, the operative technique is much the same as conventional technique, in which existing instruments and screws can be used. The internal fixator method can be applied through an open but less invasive or an MIPO approach. An indirect closed reduction is necessary when using the LCP in the internal fixator method bridging the fracture zone. A combination of both plating techniques is possible and valuable, depending on the indication. It is important to command a knowledge of both techniques and their different features.
Case based learning
