Osteoarthritis in lumbar discs
The bony spine is designed so that vertebrae "stacked" together can provide a movable support structure while also protecting the spinal cord (nervous tissue that extends down the spinal column from the brain) from injury. Each vertebrae has a spinous process, which is a bony prominence behind the spinal cord that shields the cord's nerve tissue. The vertebrae also have a strong bony "body" in front of the spinal cord to provide a platform suitable for weight-bearing. The discs are pads that serve as "cushions" between each vertebral body which minimize the impact of movement on the spinal column. Each disc is designed like a jelly donut with a central softer component (nucleus pulposus). This softer component can rupture (herniate) through the surrounding outer ring (annulus fibrosus) and irritate adjacent nervous tissue. Ligaments are strong fibrous soft tissues that firmly attach bones to bones. Ligaments attach each of the vertebrae and surround each of the discs. When ligaments are injured as the disc degenerates, pain in the area affected can result. Degenerative disc disease refers to a syndrome in which a painful disc causes chronic low back pain. The condition generally starts with a torsional (twisting) injury to the disc space. The injury weakens the disc and creates excessive micro-motion at the corresponding vertebral level because the disc cannot hold the vertebral segment together as well as it used to. The excessive micro-motion, combined with the inflammatory proteins inside the disc that become exposed and irritate the local area, produces low back pain. Unlike the muscles in the back, the disc does not have a blood supply and therefore cannot heal itself and the painful symptoms of degenerative disc disease can become chronic. While it is rare that low back pain from degenerative disc disease will progress or increase, the pain will tend to fluctuate and at times may become significantly worse. It is important to note that disc degeneration is considered part of the natural process of aging and does not necessarily lead to low back pain. MRI scans have documented that approximately 30% of 30 year olds have signs of disc degeneration on MRI scans even though they have no back pain symptoms. It must therefore be stressed that not all degenerated discs that are seen on MRI scans are pain generators. As the population ages, it is even more common for individuals to have signs of disc degeneration without pain, and by the time an individual reaches 60 years old, disc degeneration is an expected finding on an MRI scan. In fact, the incidence of low back pain actually declines as we age, despite the fact that our discs are degenerating. A fully degenerated disc no longer has any inflammatory proteins (that can cause pain) and usually collapses into a stable position. While many people over the age of 60 have degenerated discs, it is highly uncommon for them to suffer from degenerative disc disease. For most people, degenerative disc disease can be successfully treated with conservative care. Most patients will experience low-grade continuous but tolerable pain that will occasionally flare (intensify). The frequency and intensity of the flares can be managed with an exercise program that consists of: • hamstring stretching For patients who are unable to function because of the pain, or who are frustrated with their activity limitations, lumbar spinal fusion surgery is an option. Fusion surgery works because it stops the motion at a painful motion segment. A one-level fusion does not significantly change the mechanics in the back, and a two-level fusion may also be considered for patients with severe, disabling pain. Three-level fusions change the mechanics of the back substantially and are not recommended (the back is designed for movement, and limiting the movement and altering the muscle composition can in and of itself cause pain).
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