Why do lumbar discs degenerate?

People experiencing pain associated with lumbar disc issues (e.g. herniated disc, slipped disc, etc). and/or sciatica frequently associate the onset of their symptoms with a specific event.  They often cite such events as lifting, playing sports or even coughing/sneezing.

It is well accepted that it is generally “infeasible to prove a causative link between any specific inciting event and the occurrence of disc herniation.”[i]  Rather, “a cumulative injury model of disc degeneration has traditionally been predominant in spine care.” [ii]  This model suggests that most of the injury that occurs at the level of a disc occurs as a result of microtrauma that builds up in a cumulative fashion as a result of excessive forces and repeated loading.

There are several factors that feed into these excessive forces and repeated loading.  Sitting, prolonged lumbar flexion and activity-related factors certainly play a role in disc degeneration as do things like body-size, nutrition and genetics.[iii][iv]

A recent study in The Spine Journal looked at incidents people reported to be associated with the onset of low back pain symptoms.  The study reported[v]:

• 62% of lumbar disc herniation did not have a specific patient-identified event associated with the onset of symptoms
• Of the 38% of lumbar disc herniation where an inciting event was identified:
  • Nonlifting events accounted for the largest proportion, comprising 26% of all lumbar disc herniation
  • Heavy lifting - 6.5%
  • Light lifting - 2%
  • Nonexertional occurrences - 2%
  • Physical trauma - 1.3%

So, if most of lumbar disc issues (which account for a lot of the back pain that is out there) do not have clear identifiable causes, then what are we to do for prevention?  That is a complicated question, but there is good evidence for a few basic interventions.

• Modify the ways that we statically overload disc tissues
  • Avoid sitting too much
  • Avoid postures that unduly increase intradiscal pressures
  • Avoid unnecessary prolonged lumbar flexion
  • Refer to http://www.backexercisedoctor.com/journal/2010/3/23/prolonged-sitting-association-with-low-back-pain-and-propose.html for a discussion about sitting and low back pain
• Modify cardiovascular risk factors that likely feed into lumbar disc degenerative changes
  • Refer to http://digg.com/d31Lh6c for a review of nutrition and cardiovascular risk factors associated with low back pain
  • Quit smoking
• Work on exercise interventions to decrease the cumulative overloading that occurs at the level of the disc
  • Improve endurance in spine stabilizers[vi]
  • Work on abdominal bracing exercises

A recent study in the Clinical Journal of Pain looked at modifiable personal factors that predict new-onset low back pain.[vii]  The study identified a number of modifiable personal risk factors that included:

• Smoking
• Reduced back muscle endurance
• Greater posterior pelvic rotation in slump sitting

Other factors were also identified.  These factors, along with the modifiable issues identified above, are relatively straightforward things to change.

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[i] The Spine Journal 2010. 10: 1-8.

[ii] The Spine Journal 2010. 10: 1-8.

[iii] Spine. 1999 Dec 1;24(23):2468-74.

[iv] Int J Obes (Lond). 2005 Aug;29(8):903-8.

[v] The Spine Journal 2010. 10: 1-8.

[vi] Clin J Pain. 2010 May;26(4):275-83.

[vii] Clin J Pain. 2010 May;26(4):275-83.

Comments

[maigneeadvile]

Thanks!! for the good articles