The assessment and management of the failed back, Part I.

The 'failed back' represents a major clinical problem. Among the causes recognized for the 'failed back' is lateral root stenosis which has led to the use of electromyography (EMG) in the diagnosis of root compression. One hundred and thirty-two patients selected for surgical decompression were compared with 25 undergoing spinal fusion. EMG was found to be diagnostic in 95% of patients with bony canal stenosis, but only gave positive results in 62.5% of prolapsed disc patients. EMG improved in those patients who made a good recovery after surgery.