(A) Residual foraminal and (B) central stenosis after laminectomy. (A) Axial CT through a lumbar vertebra showing a bilateral midline laminectomy defect and residual foraminal stenosis on the left. (B) Axial CT showing residual central and foraminal stenosis after midline laminectomy. Note the severe facet arthritis.
trast to enhance scar tissue may also help to better demonstrate recurrent disc herniation; the recurrent disc occurs in an area rich in scar tissue, thus the enhanced scar will better delineate the non-enhanced recurrent disc. The differentiation between scar and recurrent disc is of utmost importance because surgery for an epidural scar is mostly unsuccessful, whereas surgery for a recurrent disc will result in significant pain relief in most patients.
CT is usually superior to plain X-rays for assessing bony fusion and pseudoarthrosis (Figures 17-10 and 17-11), pedicle screw placement, and residual stenosis at the operated level or at an adjacent level.
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