INTERBODY FUSION AND INSTRUMENTATION

Fusion indications in adult degenerative disk disease of the lumbosacr al spine include isolated disk resorption, primary and secondary insta bility, recurrent disk herniation, and pseudarthrosis. Common to these indications are variable proportions of biomechanical insufficiency o f the motion segment, instability, deformity, and spinal stenosis. Apa rt from favorable psychosocial and work related variables, satisfactor y outcome is dependent on treatment by a combination of diskectomy, de compression, 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 fusi on techniques. Posterior lumbar interbody fusion (PLIF) and segmental pedicle-based plate fixation overcome earlier problems with PLIF by al lowing for wide decompression and increased exposure for disk space pr eparation, minimizing neural injury. Pedicle fixation restores segment al stability and minimizes graft retropulsion. Restoration of anterior column support prolongs instrumentation life, and increases fusion ra tes irrespective of the number of levels fused. Disk space distraction , with the use of instrumentation as a working tool, permits safer dec ompression of the intraforaminal zone, a common area of stenosis, and single or multilevel deformity correction to restore coronal, axial, a nd sagittal alignment and spinal balance. Even though the surgical tec hnique is demanding, fusion rates up to 96% and clinical success up to 86% are achieved.