Degenerative Disc Disease and Low Back Pain
Degenerative Disc Disease (DDD) is a gradual process that may compromise the spine. Although DDD is relatively common, its effects are usually not severe enough to warrant medical attention. In this discussion we address DDD in the lumbar spine.
Degenerative changes in the spine are often referred to those that cause the loss of normal structure and/or function. The intervertebral disc is one structure prone to the degenerative changes associated with wear and tear, aging, even misuse (e.g. smoking). Long before DDD can be seen radiographically, biochemical and structural changes occur. Some of these changes are not unlike those associated with osteoarthritis.
Over time the collagen (protein) structure of the annulus fibrosus weakens and may become structurally unsound. Additionally, water and proteoglycan (PG) content decreases. PGs are molecules that attract water. These changes are linked and may lead to the disc’s inability to handle mechanical stress. Understanding the lumbar spine carries a large portion of the body’s weight; the stress from motion may result in a disc problem (e.g. herniation).
Degeneration of the intervertebral discs can result from a variety of conditions, including aging, trauma, and several types of arthritic conditions. As we age, our tissues tend to lose water. That’s why skin wrinkles with age, and various body parts begin to sag. When this occurs in the intervertebral disc, the disc tends to shrink, becoming thinner and less cushiony. The condition is fairly common in adults past middle age, and may be asymptomatic – causing no symptoms – other than occasional lower back pain, or stiffness. At other times, however, the associated collapse of the disc space, especially in the lumbar spine (lower back), can be the source of severe mechanical back pain, or radicular leg pain. Under these circumstances, surgical intervention may be appropriate.
The inner portion of the disc, the nucleus pulposis, is composed of proteoglycans – chemical combinations of sugar and protein. When the disc degenerates, small cracks or tears form in the outer annulus, allowing these chemical substances to leak out into the epidural space. Proteoglycans have been shown to cause irritation or inflammation of the nerves surrounding and adjacent to the damaged disc. Minimally invasive, endoscopic procedures, designed to remove the diseased or damaged portion of the disc, may be helpful in alleviating such pain.
Under other circumstances, collapse of the disc space can lead to a condition more recently termed “vertical instability”. In this case, shrinkage of the disc allows abnormal movement across a motion segment (2 vertebrae and the intervening disc), and may result in mechanical back pain – pain which arises from changes in position, or attempts at strenuous activities. In such cases, fusion of the interspace may be the procedure of choice. (Perhaps, at some point in the future, replacement of the disc by an artificial substitute may become an option, when such devices are eventually developed and approved for use, by the FDA – see below).
In some patients, the pain response may limit their flexibility. Prescribed stretching exercises can improve flexibility of the trunk muscles. Flexion exercises may help to widen the intervertebral foramen. The intervertebral (between the vertebrae) foramen are small canals through which the nerve roots exit the spinal cord. The intervertebral foramen are located on the left and right sides of the spinal column. Extension exercises, such as the McKenzie method, focuses on the muscles and ligaments. These exercises help maintain the spine’s natural lordotic curve, important to good posture.
Aerobics (no/low impact) offers many benefits including improved muscular endurance, coordination, strength, strong abdominal muscles, and weight loss. Strong abdominal muscles work like a brace (or corset) to reduce the loads to the lumbar spine. It is also known that aerobics help to combat anxiety and depression. The loads on the discs during walking are only slightly greater than when lying down. Walking, bicycling, and swimming are forms of aerobic exercise a physician may suggest.
During the acute phase of low back pain, drugs may be prescribed. Some of these may include narcotics, acetaminophen, anti-inflammatory agents, muscle relaxants, and anti-depressants. Narcotics are used on a short-term basis partially due to their addiction potential. When low back pain is caused by muscle spasm, a muscle relaxant may be prescribed. These drugs have sedative effects. Depression can be a factor in chronic low back pain. Anti-depressant drugs have analgesic properties and may improve sleep.
Today manipulation is performed by Chiropractors and Physical Therapists. For patients without radiculopathy (pain stemming from a spinal nerve root), manipulation may be effective during the first month. Thereafter, benefits are unproven. Manipulation is believed to be effective because of its effect on spinal mobility. Acute low back pain, chronic low back pain, and DDD without nerve compression may respond to manipulation.
The First Six Weeks
Usually during the first six weeks, acute low back pain is treated with a couple of days of bedrest (slightly longer with herniated disc) and appropriate medication. Muscle relaxants are seldom used for longer than one week. Early ambulation is encouraged to increase circulation (aids healing), improve flexibility, and build strength.
Generally, during the first two to three weeks the acute symptoms subside. Aerobic (no/low impact) exercise may be started three times per week along with daily back exercises. Some patients may be referred to physical therapy or a supervised work-conditioning program.
Beyond Six Weeks
If the symptoms of DDD and low back pain persist despite non-operative treatment, further diagnostic tests may be necessary. These tests may include an MRI, CT Scan, Myelogram, or possibly Discography.
Although most DDD patients with herniation respond well to non-operative treatments, a small percentage do not. Disc herniation is the most common indication for spinal surgery. In fact, 75% of all spinal surgeries are for a herniated disc.
Although degenerative disc disease is relatively common in aging adults, it seldom means a surgical sentence. When medical attention is warranted, the majority of patients respond well to non-operative forms of treatment. By eliminating tobacco and maintaining a fitness regiment along with a good diet, most people can enjoy the benefits of a healthy spine.