A series of iOO patients with pain in the leg was studied and the accuracy of electrical studies in the diagnosis of nerve root lesions was investigated before operation. The electrical studies which were performed on all the patients, included recordings of fibrillation potentials, H-reflex and ankle reflex latencies. This diagnostic technique was found to be more accurate than radiculography or clinical examination and did not give false evidence. Seventy patients were classed as having a lesion of the nerve root. Fifty ofthese patients were treated surgically. The operation revealed compression ofthe nerve root by osteophytes arising from degenerative and incompletely dislocated posterior facetjoints in 43 patients.

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.