Many patients with low back pain have increased symptoms after sitting for a long time (30 to 60 minutes). One patient in 70 will tell the doctor, “My pain comes on as soon as I sit down, and it goes away when I stand up.”
Doctors in France may be the first to link this pain pattern with lumbar instability. Instability means that there is abnormally increased motion at one or more spinal levels.
Finding the level of instability isn’t easy. The doctor uses palpation (feeling with the hands and fingers) and X-rays or other imaging methods to decide where the instability is located. Two kinds of motion of the lumbar vertebrae were measured in this study: translation and rotation.
Translation is the sliding motion of one vertebra over another. Rotation is a twisting motion. An increase of 10 percent or more of translation motion is a sign of lumbar instability. Patients with instability also had twice as much rotation as the control group (who had no back pain).
This study shows that pain while sitting that goes away by standing is a sign of lumbar instability. The unstable motion can be sliding or twisting. It’s unknown if the higher level of motion causes pain or if pain causes increased motion.
The authors of this study say it’s easier to measure translation than rotation. X-rays to find lumbar instability should not be taken with the patient in the painful sitting position. The X-rays are harder to focus and may cause error in interpreting the results.
Treatment for lumbar instability starts with physical therapy. Special stabilizing exercises are used. Changes in posture are made for many patients. If this treatment fails, surgery to fuse the unstable segment may also be an option.