Research Review By Dr. Shawn Thistle©

Date Posted:

April 2010

Study Title:

The association between lumbar disc degeneration and low back pain

Authors:

de Schepper EIT, Damen J, van Meurs JBJ et al.

Author's Affiliations:

Departments of General Practice, Intern Medicine, and Radiology – Erasmus MC, Rotterdam, The Netherlands.

Publication Information:

Spine 2010; 35(5): 531-536.

Background Information:

Lumbar disc degeneration has been proposed as a possible risk factor for LBP – with reported odds ratios estimated between of 1.3 and 3.2 (1). However, most studies contributing to this estimate are of low methodological quality.

Lumbar disc degeneration (LDD) is characterized by the presence of endplate sclerosis, osteophytes and disc space narrowing. The relative importance of each of these individual radiological features (IRF) has not yet been established, nor studied in a prospective way in the same patient sample. As such, we are currently not sure how to combine these IRFs to arrive at a meaningful definition of LDD, particularly one that can relate to the clinical presence of low back pain (LBP).

There is also uncertainty about whether the lumbosacral disc should be included in such evaluations. Clarifying these queries was the goal of this study – which explored the association of the IRFs with self-reported LBP.

Pertinent Results:

  • lumbar radiographs were assessed and scored for 1204 men and 1615 women (average age of the sample as a whole was ~ 65 yoa)
  • osteophytes were the most frequent radiological finding, and were more prevalent in men (95% vs. 91% in women)
  • disc space narrowing was more common in women (65% vs. 53% in men)
  • both osteophytes and disc space narrowing increased with age
Associations with Low Back Pain:
  • the presence of ≥ grade 2 osteophytes in men or women was NOT significantly associated with back pain
  • disc narrowing was associated with back pain in men (OR = 2.4) and women (OR = 1.7)
  • the presence of both ostephytes and disc space narrowing was associated with back pain in men (OR = 2.2) and women (OR = 1.9) – notice how combining the two factors did not really alter the odds ratios compared to narrowing alone
  • the strength of almost all associations was stronger in those patients reporting chronic LBP
  • the strength of association also increased when excluding the L5-S1 disc, particularly for disc space narrowing (that is, narrowing at other levels was more strongly associated with LBP)
  • disc narrowing was more associated with LBP in men aged 55-64, while in women the association was stronger in an older age group (65-74)

Clinical Application & Conclusions:

This study was one of the first to report different definitions of LDD (i.e. single vs. multi-level disc narrowing, ± the L5/S1 level) and how they relate to LBP in a large sample.

The literature to date on the association of osteophytes and LBP is inconclusive – not to mention whether treatment can reverse such changes (Take note those of you who use such findings to convince patients to commit to excessive treatment plans! Not that any RRS reader would do that…).

This study adds to previous literature by suggesting that disc narrowing, particularly at multiple levels, may be a more important finding and that the presence of osteophytes alone does not seem clinically relevant for LBP. It is worth noting here that this study could not establish whether the presence of LDD could predict LBP over time.

The authors suggest that reduced disc space may be more likely to increase forces on facets and intervertebral ligaments, thus causing more pain. Further research is required to evaluate this hypothesis.

The authors also propose that removing the L5/S1 disc from analysis may strengthen the associations in this study because the narrowing of this level is often overstated (this disc is normally narrower than L4-L5). Further, the literature suggests that this disc exhibits the most variability in relative size compared to other lumbar levels, regardless of disease status (2).

Overall, clinicians can take the following general take home points from this study:
  • disc space narrowing appeared to be moderately associated with LBP (more than osteophytes), particularly in men
  • disc space narrowing at 2 or more levels appeared to more strongly associated with LBP than single level narrowing
  • the strength of associations increased in those with chronic LBP
  • the majority of associations are strengthened by removing the L5/S1 disc from the analysis

Study Methods:

The data for this study originated from the Rotterdam Study, a large, open population, prospective cohort study of people aged 55 and older. Of 7983 participants examined, 2819 were selected on their availability for radiographic follow-up at 6.6 years. Each subject had lateral lumbar radiographs, body mass index (BMI) and bone mineral density (BMD) testing at study inception.

Ample demographic and clinical information, including the presence of LBP was also collected. LBP history was assessed via personal interview. Chronic LBP was classified as pain lasting longer than 1 year.

On the radiographs, each vertebral level from L1/2-L5/S1 was assessed for the presence of osteophytes and disc space narrowing (NOTE: sclerosis was not assessed in this study due to previous reports of poor intra-examiner reliability [via ICC]) (3). All radiographs were assessed by a single radiologist, with a random selection of 140 radiographs also assessed by another radiologist to assess inter-observer reproducibility (ICC was 0.83 for osteophytes and 0.77 for disc space narrowing, indicating good reproducibility).

Disc space narrowing was defined as present if a grade of mild, moderate or severe was given. Due to the low number of radiographs without osteophytes, a higher cutoff value was used for this (minimum grade 2 instead of 1). The lumbar spine was evaluated as one unit with 5 subunits, so the lumbosacral disc could be excluded for a second statistical analysis to assess its importance.

All analyses were presented as odds ratios, stratified for gender and age group. BMI was also adjusted for, as high BMI is thought to affect LDD.

Study Strengths / Weaknesses:

The authors appropriately discuss the following strengths and weaknesses that should be considered when interpreting the results of this study.

Strengths:
  • the sample size was large
  • standard radiographs were used with only one evaluator to maintain consistency (this evaluator was blinded to all other clinical data)
Weaknesses:
  • a selection bias for healthy participants may have occurred – subjects had to physically be able to attend follow-up sessions (as much as 6.6 years from study inception), which may have precluded those with more severe symptoms from being included
  • no frontal lumbar radiograph was used (the relevance of this is controversial within the literature)

Additional References:

  1. van Tulder MW, Assendelft WJ, Koes BW et al. Spinal radiographic findings and nonspecific low back pain: A systematic review of observational studies. Spine 1997; 22: 427-434.
  2. Frymoyer JW, Newberg A, Pope MH et al. Spine radiographs in patients with low back pain: an epidemiological study in men. J Bone Joint Surg Am 1984; 66: 1048.1055.
  3. Lane NE, Nevitt MC, Genant HK et al. Reliability of new indices of radiographic osteoarthritis of the hand and hip and lumbar disc degeneration. J Rheumatol 1993; 20: 1911-1918.