Bending or twisting?
In a recent bending study in Clinical Biomechanics, researchers looked at how the nucleus pulposus deformed as the vertebrae rotated at two lumbar levels: L1-2 and L4-5. They were curious about how the nucleus pulposus behaved as this hydraulic tissue has an important role in resisting compression with bending and twisting of the spine.
Rotation is often described as a body position to predispose low back injury but there is not much research on the topic to demonstrate this is actually the case.
There has also been mounting evidence that flexion bending is thought to be a mechanism for disc injury and this Flexion load is thought to be more important.
Coupling movements of both flexion AND rotation has historically been thought to be the worst.
These researchers led by Fazey, P. used MRI to look at 10 asymptomatic subjects of an average age of 29 yrs.
What these researchers determined was that side-ways bending demonstrated greater nuclear deformation compared to rotation. They also showed that the nucleus moves backwards when one bends forwards and moves forwards when one bends backwards. Opposite.
One of the take home messages from this study is that lateral flexion (or side-ways movement) of the spine causes the nucleus structure to deform more than twisting. Therefore, patients should be instructed to minimize sideways bending to help reduce the deformation of the nucleus pulposus.
This study is one example of why Dynamic Disc Designs has worked to showcase the anatomy and inner workings of human discs. Our latest is the Centralizer. Degeneration is as a result of annular fissures and understanding how to minimize annular stress will likely lead to better outcomes for pain practitioners.