Is Low Back Pain Caused By Spinal (Facet) Joint Arthritis?Investigators looking for the cause of low back pain (LBP) say there's reason to believe the source could be the lumbar facet (spinal) joints. But the evidence is circumstantial. Injecting a numbing agent and antiinflammatory drug in or around the joint does produce pain relief. They interpret this to mean the origin of the pain is the facet joint.
But questions remain. They have not been able to show that there's a direct correlation between the degree of arthritis present and the amount of pain relief experienced. Is the pain really coming from the lumbar facet joints? Is it because there are arthritic changes in the joint? Or is there something else going on?
In this study, CT scans of facet joints were taken of men and women ages 40 to 80 who were already participating in the famous Framingham Heart Study. The Framingham study started in 1948 in Framingham, Massachusetts. Over 5,000 adults between 30 and 60 years old were enrolled. They were interviewed, examined, and tested once every two years. The original participants are dead now, but their families continue to participate in the study. Three generations of families have been part of the study.
The group who were part of this low back pain study had been part of a larger group who had 8-slice multidetector CT scans done of the heart and coronary arteries. Those who indicated on the questionnaire that they had suffered low back pain in the last 12 months were enrolled in this separate study. They had a similar multislice CT scan of the abdomen, which included all of the lumbar facet joints (both sides).
Results were carefully analyzed and compared between patients with and without low back pain. CT scans were used instead of the more standard X-rays because they show both sides of the joint surfaces. Any bone spurs, overgrowth or thinning of the joint cartilage, and cysts show up clearly on CT imaging. Hardening of the joint capsule called calcification is also observable.
This study helped answer quite a few questions. It showed how common facet joint osteoarthritis is in adults based on age. For example, one-fourth of the adults younger than 40 years old had degenerative joint changes. An even greater percentage (74 per cent) of adults between 40 and 49 years old had signs of degeneration. And by the time they reached age 70 and older, 69 per cent were affected.
The areas affected most often were in the low lumbar (L45 and L5S1) regions. Severity of facet joint osteoarthritis was graded as zero (normal), one (mild degenerative changes), two (moderate degenerative disease), or three (severe changes). Besides seeing an increasing number of people affected as they got older, women of all ages were more likely to have facet joint osteoarthritis than men.
Other studies have linked hormone differences that may account for the gender differences. Cartilage is sex-hormone-sensitive tissue. There are more estrogen receptors on the facet cartilage of women. The effect of this hormone is to increase motion at the joints. For example, in the lumbar spine, women have more bending motion forward and to the side and more extension backwards. More segmental motion of the vertebrae and facet (spinal) joints leads to more wear and tear and thus, a greater amount of degeneration.
But none of the findings presented here were linked with the presence of low back pain. And that was a new and major finding of this study. The clinical implications aren't clear yet. In other words, this information doesn't change how we treat low back pain. There's still the fact that facet joint injections have a positive benefit. Why that is so if the facet joints don't generate pain remains to be explored and explained.
Leonid Kalichman, PT, PhD, et al. Facet Joint Osteoarthritis and Low Back Pain in the Community-Based Population. In Spine. November 1, 2008. Vol. 33. No. 23. Pp. 2560-2565.
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