Lumbar disc degeneration: association between osteophytes, end-plate sclerosis and disc space narrowing

Background: Lumbar disc degeneration is characterised radiologically by the presence of osteophytes, end-plate sclerosis and disc space narrowing. Aim: To determine the strength of the association between increasing severity of combinations of these features in a population sample of men and women. Methods: Men and women aged >= 50 years were recruited from a primary care-based community health index in Aberdeen, UK. Participants had lateral spinal radiographs performed according to a standard protocol. The intervertebral disc spaces (L1/2-L4/5) were evaluated for the presence of anterior osteophytes, end-plate sclerosis and disc space narrowing using a graded semiquantitative score (grade 0-3). Log linear modelling was used to determine the associations (pairwise) between increasing severity of these features, with the results expressed as beta coefficients and 95% confidence intervals (CIs). Results: There were 286 men (mean age 65.3 years) and 299 women (mean age 65.2 years) with spinal radiographs, yielding a total of 2340 assessable lumbar vertebral levels. In all, 73% of vertebral levels had evidence of osteophytes, 26% of sclerosis and 37% of disc space narrowing. Increasing severity of osteophyte grade was associated with an increasing severity both of sclerosis and of disc space narrowing, whereas the severity of sclerosis was associated with the severity of narrowing. This was true at all vertebral levels. The strongest association, however, was between osteophytes and sclerosis (beta coefficient =2.7, 95% CI 2.4 to 3.1). For sclerosis and narrowing the beta coefficient was 1.9 (95% CI 1.7 to 2.1), whereas for osteophytes and narrowing the beta coefficient was much weaker at 1.2 (95% CI 1.1 to 1.3). There was no important influence of vertebral level on any of these associations. Conclusion: The association between increasing severity of osteophytes and end-plate sclerosis is stronger than for other combinations of radiographic features of lumbar disc degeneration.