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ABSTRACT: This article illustrates the application of the Wiltse pedicle screw fixation system and the general principles of pedicle screw insertion. The system is designed for stabilization of the lumbosacral spine. Indications, complications, and personal results are reviewed.
Special problems confront surgeons who perform adult reconstruction of the lumbar spine. A high rate of pseudarthrosis complicates simple fusions of this highly mobile area. Instability in this area, especially following surgical decompression, causes pain, deformity, and fusion failures. Distraction instruments have caused problems by eliminating lumbar lordosis. The lack of posterior structures following decompression in the lumbar spine sometimes precludes the use of distraction instrumentation or segmental wiring. These and other complications have impeded the use of instrumentation, although many believe that rigid internal fixation increases the success of fusion mass consolidation.
Pedicle screws were first used in the 1950s. They have been reintroduced recently and have the advantage of solid fixation to vertebral bodies from a posterior approach. Pedicle screws do not rely on posterior elements, nor do they require distraction or compression to hold a position rigidly. The Wiltse System relies on pedicle screws connected to stainless steel rods by saddle clamps (Fig. 1). Once the screws are inserted, a soft aluminum mastering rod is fastened into the saddle clamp on each pedicle screw. The aluminum master creates a precise model of the spinal contour. The model is then taken to a special bending apparatus and a perfect stainless steel replica is made. The replica is positioned along the pedicle screws and the saddle clamps are again tightened.
The Wiltse System has several distinct advantages over other pedicle screw fixation systems. The rod/ saddle/screw junction provides rigid transfer of load, decreasing the chance of loosening or fatigue fracture within the system. The use of rods allows adaptability to spinal contour despite severe deformity (Fig. 2). Because of the saddle size and orientation, the superior facet joint of the instrumented cephalad vertebra always remains undisturbed. The system also makes it possible to reduce displaced vertebrae.
Another unique feature is that either one or two rods can be used on each side of the spine ie, two or four rods in total (Fig. 1). Each of these methods has certain advantages. The advantage of...