100 lumbar spines taken out from post mortem specimens have been studied. They were radiographed in various positions of flexion and extension, and the stability of the spines, i.e. of the discs, was assessed. Other radiographic changes were also recorded. The intervertebral discs were sectioned horizontally, and the changes observed in the nucleus pulposus and annulus fibrosus were recorded. Particular attention was paid to ruptures in the annulus fibrosus.

The records of 15,160 patients seen in the Clinic for lumbar pain, excluding those with tuberculosis and tumours, during the period 1936-1946, hare been collected:​ and the incidence of radiographic signs of disc degeneration in the lumbar spine has been studied.

The post mortem material showed:​

1. Disc degeneration acquires patho-anatomical importance when the annulus fibrosus begins to rupture.
2. In the lower lumbar discs the ruptures in the annulus were mostly localised to the posterior part of the disc. From the centre they were directed either sagittally or laterally backwards to the intervertebral foramen. In the upper discs the ruptures were frequently also anterior.
3. Marked degeneration may be present without any radiographic changes. Thus a normal radiograph does not exclude an important degeneration in a disc.
4. In 16 out of 17 cases with instability there were severe changes in the disc and ruptures in the posterior part of the annulus fibrosus.
5. When the radiograph showed reduced disc space, sclerosis or osteophytes, the corresponding disc was severely damaged.
6. In cases with prolapse of the disc the structure had the same patho-anatomical characteristics as in cases of simple degeneration. Disc prolapse is a part phenomenon of degeneration of the disc.

The clinical material showed :​

1. Radiographic disc degeneration was found in 39 % of all the patients that came to the Clinic for “back trouble”, and in 50 % of the material covering the last 2 years of the investigation.
2. 43 % of the cases with disc degeneration were women, and 57 5% men.
3. 74 % of the men were engaged in physical work of some kind or other. This proportion agrees roughly with the country’s proportion of labourers.
4. The authors found no evidence that heavy physical work is the direct cause of the disc changes.
5. Disc degeneration occurs most frequently (in 47.6 %) in the 4th lumbar disc, and in 75.2 % in the 4th and 5th discs together.
6. In 15 % instability was the only radiographic change. In 70.3 % [of these] it occurred at the 4th disc.
7. The investigation shows that radiography does not give satisfactory information on the condition of the disc in cases of lumbar pain. The instability test is a valuable contribution to diagnosis.