Disc degeneration. Its frequency and relationship to symptoms.

Degenerative changes in the intervertebral discs have been recognized by pathologists for a considerable time. They were described by Wenzel (1842) and were also studied by Rokitanski (1855) and by many other pathologists. Extensive studies by Schmorl (1929), begun in Dresden in 1925 on routine autopsy material, revealed the great frequency of degenerative changes in the intervertebral discs and their relationship to disc prolapse (Schmorl and Junghanns, 1951). According to Schmorl, disc tissue is normally the first to show signs of the ageing process. Even in the middle decades of life completely normal discs are the exception rather than the rule. At routine autopsies degenerative discs are found in 10 per cent. of persons aged 20 to 29, and there is an increase with age to 96 per cent. in those over the age of 60. Emphasis in the past has been mainly on disc prolapse and little attention has been paid to degenerative disc changes unassociated with prolapse, though it has been recognized that in many instances of sciatic and brachial pain no protusion is found at operation. Radiological evidence of disc degeneration has been observed since x rays first began to be used. As osteophyte formation is a prominent feature, the label osteoarthritis was at first applied. Collins (1949) suggested that the term osteoarthritis be restricted to degenerative changes in the diarthrodial joints of the spine and that disc degeneration be used for such changes in the intervertebral discs. This seems preferable to the use of generic terms, such as spondylosis, spondylarthrosis, and osteophytosis intervertebralis, for there is evidence that the aetiology of degenerative disease in apophyseal joints and discs may not be identical (Kellgren and Lawrence, 1958). Some authors, however, have restricted the term spondylosis to degenerative processes in the vertebral bodies and intervertebral discs (Payne and Spillane, 1957; Wilkinson, 1960). This is acceptable but would seem to have no advantage over Collins' terminology. The relationship of x-ray changes of disc degeneration to symptoms was first investigated in a survey of rheumatic complaints in coalminers, submitted to routine x ray examination of the cervical and lumbar spine, and the importance of disc degeneration as a cause of both symptoms and incapacity in this occupational group was demonstrated (Kellgren and Lawrence, 1952). Later a population sample in Leigh in Northern England, in which the cervical, dorsal, and lumbar spine were examined, was reported (Lawrence, de Graaff, and Laine, 1963). In this population the 8th dorsal disc was most commonly affected in males and the D7 in females, but there were two further peaks, one at C6 and the other at L3. The cervical and lumbar spine were more frequently affected in males and the dorsal in females, and the prevalence at all sites increased with age. There was a relationship between cervical disc degeneration and neck-shoulder-brachial pain, and between lumbar disc degeneration and back-hipsciatic pain, particularly in the younger age groups, but the numbers in some age groups were too small for a definite conclusion to be reached. A history or signs suggestive of neurological involvement was comparatively rare, and it was concluded that symptoms arose from strains of adjacent ligaments as a result of mechanical defect from unstable or narrowed discs rather than from nerve root pressure. Caplan, Freedman, and Connelly (1966), from a survey of lumbar spine x rays in miners, concluded that disc degeneration, as measured by disc narrowing, is not an accompaniment of age, though there was a direct relationship between ageing and body spurring.