Isolated lumbar disk resorption as a cause of nerve root canal stenosis.

In established isolated disk resorption at the lumbo-sacral junction, nerve root canal stenosis affects predominantly the S1 nerve which becomes obstructed between the inner margin of the superior facet of S1 and the buckled ligamentum flavum behind and by the ridge of the remaining annular fibers in front. However, in addition, there may also be an intervertebral foramen stenosis involving the L5 nerve at this level. Accordingly, in planning the surgical treatment of this condition where bilateral buttock and leg pain has become intractable or frequently recurrent, and where back pain is not major concomitant of the symptom complex, the surgeon must remove the inner and superior margins of the S1 facet together with the whole of the ligamentum flavum, thereby decompressing both L5 and S1 nerve roots. The operation involves a partial facetectomy only at the affected level and spinal stability is not impaired.