Fusion indications in adult degenerative disk disease of the lumbosacral spine include isolated disk resorption, primary and secondary instability, recurrent disk herniation, and pseudarthrosis. Common to these indications are variable proportions of biomechanical insufficiency of the motion segment, instability, deformity, and spinal stenosis. Apart from favorable psychosocial and work related variables, satisfactory outcome is dependent on treatment by a combination of diskectomy, decompression, and deformity correction, in addition to fusion. Isolated intertransverse or interbody fusions show variable fusion rates that are increased by concurrent instrumentation. Persistent pseudarthrosis rates and instrumentation failures have prompted circumferential fusion techniques. Posterior lumbar interbody fusion (PLIF) and segmental pedicle-based plate fixation overcome earlier problems with PLIF by allowing for wide decompression and increased exposure for disk space preparation, minimizing neural injury. Pedicle fixation restores segmental stability and minimizes graft retropulsion. Restoration of anterior column support prolongs instrumentation life, and increases fusion rates irrespective of the number of levels fused. Disk space distraction, with the use of instrumentation as a working tool, permits safer decompression of the intraforaminal zone, a common area of stenosis, and single or multilevel deformity correction to restore coronal, axial, and sagittal alignment and spinal balance. Even though the surgical technique is demanding, fusion rates up to 96% and clinical success up to 86% are achieved.
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