Update On Lumbar Disc DiseaseIn this update on lumbar disc disease, the authors start out with a detailed review of the normal, healthy disc anatomy. Four tissue layers are described and discussed. These include the outermost annulus, the inner annulus, the transitional zone, and the gel-like nucleus pulposus.
The intact disc provides support for the spine and acts as a shock absorber. The discs also transmit and transfer force and load on the spine. In contrast, the degeneration of the disc occurs slowly over time. This reduces the effectiveness of the discs to accomplish these tasks.
The nucleus starts to lose fluid and dry up. A damaged disc cannot spread the load evenly. The result is even more strain on the disc structures. Besides the breakdown that occurs naturally over time, there are other risk factors.
It turns out that smoking (once thought to be the number one risk factor in disc degeneration) is only a minor player. Likewise, heavy lifting isn't a big risk factor. In fact, competitive weight lifters have fewer problems with disc degeneration than the general adult population.
Genetics (positive family history) is highly linked with early onset of herniated lumbar disc. Patients with disc herniation before age 21 are five times more likely to have a close family member with this same condition.
So, what really happens with disc degeneration? A key factor is nutrition and fluid loss. Over time, the disc loses the ability to exchange fluids properly. Thin fibers are replaced with thick ones. Cross-links form between layers of tissue. These links bind the disc layers together and prevent smooth, fluid movement.
Eventually, there is a loss of stiffness and fluid pressure. Bulging, herniation, and decreased disc height occur as a result. The endplate starts to give way. The endplate is a protective piece of fibrous cartilage between the disc and the vertebral bone. The endplate helps move nutrients into the disc and waste products out.
The authors present MRI pictures of various disc problems. Annular tears and displaced nuclear material lead to changes in the nearby soft tissue structures. Even a small change in the disc height can create change in the facet joints, foramen (opening for spinal nerve roots), and supporting ligamentous structures.
Not everyone has painful symptoms with disc degeneration. Figuring out which structures are causing the pain can be difficult. Knowing how to treat the problem is even more challenging. Lumbar stabilization exercises seem to work well when done properly.
Studies are ongoing to find the most effective treatment methods for degenerative disc disease. Some of the approaches under investigation include exercise, traction, and lumbar manipulation. Injection of growth factor or stem cells into the discs is being done on animal models at the present time.
Paul Beattie, PT, PhD, OCS. Current Understanding of Lumbar Intervertebral Disc Degeneration: A Review with Emphasis Upon Etiology, Pathophysiology, and Lumbar Magnetic Resonance Imaging Findings. In Journal of Orthopaedic & Sports Physical Therapy. June 2008. Vol. 38. No. 6. Pp. 329-340.
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