From: Spine (Phila Pa 1976). 2010 Mar 1;35(5):531-6.
Back pain is one of the most common musculoskeletal complaints of the elderly, with a point prevalence of 26.9% in the Netherlands. Van Tulder et al performed a systematic review and reported that lumbar disc degeneration could be a possible risk factor for back pain in adults. However, the review reported that the methodologic quality of most of these studies was low and the studies were difficult to compare due to difference in gender frequencies, age groups, settings, radiographic grading systems, and definitions for lumbar disc degeneration.
Lumbar disc degeneration is characterized radiologic by the presence of osteophytes, endplate sclerosis, and disc space narrowing. In 1993, Lane et al presented a reliable grading system for these individual radiographic features. In a recent review, this grading system was recommended for use in epidemiologic studies. There have been a number of recent studies that have used the classification of the individual radiographic features of disc degeneration defined by Lane et al. One of these studies described the occurrence of these separate features and their relationship with back pain in the open population, but only in a limited sample.
However, it is still unknown how to combine the individual radiographic features and how to define a clinically relevant definition for lumbar disc degeneration. Currently there is no consensus about whether the lumbosacral disc should be scored. Some studies have included the lumbosacral level in their definition of lumbar disc degeneration, while others have not. Currently within the literature, there have been no studies that have explored different definitions of lumbar disc degeneration and their association with low back pain within one study sample.
The purpose of this study was to explore the association of the different individual radiographic features, including osteophytes and disc space narrowing, with self-reported low back pain. Different definitions of lumbar disc degeneration with self-reported low back pain and disability were considered in a large open population sample. Furthermore, in order to disentangle the discrepancies in reported strength of the associations, the authors characterized the frequency of the different individual radiographic features of lumbar disc degeneration and definitions of lumbar disc degeneration, as well as their association with low back pain status, by age, gender, and vertebral level.
The authors are the first to report in one paper, multiple lumbar disc degeneration definitions and their associations with low back pain, for the separate genders and discreet age groups. In this study, disc space narrowing appeared to be more strongly associated with low back pain than osteophytes, especially in men. Disc space narrowing at 2 or more levels appeared more strongly associated with low back pain than disc space narrowing at only 1 level. The strength of the associations increased with chronic low back pain. The majority of the associations were strengthened by excluding level L5–S1.
The most frequently observed radiographic feature of lumbar disc degeneration was osteophytes, with greater frequency in men than in women. Narrowing, however, was more common in women than in men and was also shown to be more frequent at the lower disc levels. Both individual radiographic features increased in frequency with age.
Data from many studies suggest an association with lumbar disc degeneration and low back pain. The authors are not aware of data from population-based samples that have investigated the association of different definitions of lumbar disc degeneration with self-reported low back pain. MacGregor et al performed a study, using MRI scans to assess risk factors associated with severe back pain. They investigated a number of features including; disc height, signal change, disc bulge and anterior osteophytes, and made a sum score for all features together. This sum was associated with severe back pain. However, they did not state which features had the highest predictive capability. Some studies suggest an association between osteophytes and low back pain and some studies suggest an association between disc space narrowing and low back pain. The data from this study confirms the association between low back pain and disc space narrowing. In addition, the data suggest an association with osteophytes, only when a more specific definition (osteophytes) is used. However, when osteophytes and disc space narrowing were both included in the model, there was no association with osteophytes anymore. Therefore osteophytes do not have an independent association with low back pain and seem therefore an inferior derivate from disc space narrowing.
Some studies suggest that the strength of the association between low back pain and disc space narrowing grows with increasing severity of disc space narrowing. Data from this study confirm this, but only when L5–S1 is excluded. Further, the data indicate that the association between low back pain and disc space narrowing increases when a greater number of levels are affected.
The explanation for the stronger association between low back pain and disc space narrowing compared with the presence of osteophytes is unknown. It is possible that the reduction of space between the vertebrae as a consequence of the degenerative disc is more likely to lead to increased pressure on facet joints and spinal ligaments.
The explanation for the stronger association between back pain and disc space in men compared with the association in women is also unknown. It is possible that even though women reported low back pain more often, only a small proportion of the complaints are due to lumbar disc degeneration, whereas other factors determine the feeling of pain. Men and women could also report pain differently therefore effecting the association between back pain, disc space narrowing and gender. Cecchi et al showed that women presented with significantly more severe pain than men.
A possible explanation for the stronger association between low back pain and disc space narrowing, excluding level L5–S1, is the possible overrating of the narrowing grade of the lumbosacral disc. The height of the lumbosacral disc is difficult to score due to its narrowed height relative to disc L4–L5. The lumbosacral disc is also different in appearances among different individuals, independently of disease. Therefore, by using the lumbar disc definition “narrowing 1 to 4,” the inconsistency of the grading scores at this level is ruled out. Furthermore, some differences in the reported associations in the prior studies can be explained by the stratified results. Possible explanations for relatively low odds ratios previously reported could be due to the use of a young age group, the use of women only and scoring of the lumbosacral level.
Data from this study confirms the findings from recent population based radiographic surveys showing a greater frequency and severity of osteophytes in men than in women. A possible explanation for the greater frequency in men is the higher BMD in men. However, after including BMD in the model, although less explicit, men still show a greater frequency and severity of osteophytes.
Data from this study suggest a greater frequency and severity of narrowing in women than in men and confirms that the prevalence of osteophytes and disc space narrowing increases with age in both men and women.
The authors defined chronic low back pain to be present when the duration of the low back pain was more than 1 year. In this way the definition chronic low back pain included long lasting chronic complaints with long lasting impact on ones life. When they defined chronic low back pain to be present when the duration of the low back pain was more than 6 months, the OR of the associations diminished.
From this data, a useful case definition for lumbar disc degeneration can be deduced; specifically disc space narrowing at 2 or more levels from L1/2 to L4–L5. This definition shows the strongest relationship with low back pain and represents a more generalized form of lumbar disc degeneration. As a result it might be a promising clinically relevant phenotype in genetic and epidemiologic lumbar disc degeneration research.
The data provides evidence for a moderate association between disc space narrowing and low back pain. This association is only slightly less than the association of pain and radiologic knee osteoarthritis and even slightly more than the association of pain and radiologic hand osteoarthritis in the same population sample.
The most important aspect of the data are that disc space narrowing at 2 or more levels is even more related to chronic low back pain. The ability of lumbar disc degeneration in predicting low back pain at the follow-up period was unfortunately not possible to investigate, as no questions about low back pain specifically were asked at the follow-up visit.
The data provides evidence for an association between disc space narrowing and low back pain especially in men, with the association increasing, with increasing numbers of affected intervertebral disc spaces. The data highlights the frequent occurrence of individual radiographic features, as well as the increased frequency in age, of the individual radiographic features of lumbar disc degeneration in population samples of men and women.
