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.