Lumbar monoradiculopathy due to unilateral facet hypertrophy.

Twenty-two patients presented during the last 3 years with unilateral symptoms and signs of a lumbar monoradiculopathy indistinguishable from those of a disc herniation. All had compression of the nerve root posteriorly by a hypertrophic facet without anterior compression from the disc. None of the patients had spinal claudication. Preoperative evaluation with computed tomographic (CT) scanning was disappointing as the pathology was correctly defined in only 1 of 10 patients. Lumbar myelography was helpful, but did not always localize the lesion. The decision to operate was based primarily on the clinical grounds of persistent or progressive radiculopathy. The operative techniques used were two-level hemilaminectomy in 7 patients, single level laminectomy in 4, and multilevel laminectomy in 11. Surgical exploration revealed that the site of compression ranged from the medial canal to the lateral recess. The root was compressed by inferior facets 8 times and by superior facets 14 times. Back pain was relieved in 12 of 15 patients, and leg pain was relieved in 19 of 21. Neurological deficit was relieved in 19 and improved in 3. It is concluded that standard CT and myelographic techniques may not anatomically define the point of radicular compression. Intraoperatively the root must be explored from its dural origin to a point beyond the pedicle to ensure adequate decompression. Most, but not all patients with hypertrophic radicular compression will improve after surgical decompression.