Cerebrospinal fluid concentrations of lidocaine after its systemic bolus delivery in humans indicate that the spinal cord may be the major site of antinociceptive action by this route of drug administration.

This study retrospectively reviewed the outcomes of 17 patients with postlaminectomy lumbar instability treated by transpedicular reduction and stabilization. The criteria of instability were defined strictly by both the clinical symptom of "instability catch" and the radiological findings that fulfilled Nachemson's criteria. Low back pain and/or sciatica that interfered largely with the patients' work or quality of life were the indications for this treatment. All the operations were performed by one surgeon with the same spinal instrumentation system-"AO internal fixator". The follow-up period was between 16 and 36 months (mean 24 months). Face to face questionnaire revealed that this treatment modality is encouraging. Fourteen patients (82%) had complete or nearly complete relief from all the pre-operative symptoms. Two (12%) had partial relief of the symptoms that required a subsequent discectomy or wider laminectomy. Only one case (6%) with osteoporosis remained unchanged after the operation. On the follow-up radiographs, sixteen patients (94%) showed good alignment and solid arthrodesis of the treated motion segment. These radiological findings correlated quite well with the absence of the clinical symptom of "instability catch". A common, but acceptable, complication found in this series was a variable degree of low back stiffness secondary to the instrumentation. Fracture of the screw was found in one patient and pull out of the screw was found in another patient. However, they did not elicit detectable symptoms. Osteoporosis, concomitant disc herniation and persistent spinal stenosis at/or adjacent to the operated level were the three main factors that may contribute to unsatisfactory results secondary to this treatment. These problems remain to be resolved in the future.