Posterior protrusion of one of the lumbar intervertebral discs into the spinal canal is one of the most common mechanical derangements of the low back in patients suffering from intractable sciatic pain. The leg pain is due to direct pressure of the displaced intervertebral-disc tissue on one or more roots of the cauda equina. In addition to this lesion, there may be found associated thickening of the ligamentum flavum, chronic adhesive arachnoiditis, hypermobility of the involved vertebrae, and oedema of the involved nerve roots. Although the etiology of posterior disc protrusions is not perfectly clear, trauma to and degenerative changes in the intervertebral discs alone or in combination seem to be the usual causes of posterior protrusion.

Among the most common and characteristic symptoms and signs, are intractable sciatic pain following a lifting injury, accompanied by limitation of back motion and of straight-leg raising, sciatic scoliosis, and lumbar kyphosis, tenderness over the lower lumbar spinous processes, and absence of the ankle jerk. The total protein of the spinal fluid is usually elevated. There are no changes on the routine roentgenograms characteristic of ruptured intervertebral discs, but narrowing of the fourth lumbar disc is of some importance if the clinical picture is characteristic. Lipiodol examination is highly accurate in making the correct diagnosis and in localization of the lesion, but because of potential danger, the use of lipiodol should be reserved for cases in which surgery is necessary. Pneumomyelography and clinical localization of the lesion may make the use of lipiodol necessary in not more than one-half the cases. Conservative treatment should be tried in every case of suspected protrusion of the intervertebral discs unless there is obvious serious nerve-root pressure, as shown by objective sensory or motor disturbance. Bed rest and immobilization of the lumbar spine in a plaster jacket seem to be the most effective means of conservative treatment.

Surgical treatment consists in the removal of the ruptured disc fragment through as small a laminectomy incision as possible. Spine fusion at the time of the laminectomy seems to give definitely better results than laminectomy alone.

Of ninety-four cases of proved ruptured intervertebral disc followed for at least one year after operation, 77 per cent. had complete relief of sciatic pain, and an additional 18 per cent. had only minor leg pain. There were two proved cases of recurrent ruptures in this series.

The relief of back symptoms was not as satisfactory as the relief of the radiating leg pain. Seventy-three per cent. of the patients in whom the spine was fused and 52 per cent. of the patients without fusion had no back symptoms. The rest had complaints of backache or weakness of varying severity. In a small series in which insurance compensation was involved, 45 per cent. of the patients have been returned to their original occupation.