Your spine is a strong, resilient structure made up of vertebral bones alternating with fibrous discs (Figure 1). These discs continually absorb shock as you move. This shock, which is really just the transfer of energy, is usually minimal. For instance, as a letter carrier walks his or her route, the spine absorbs kinetic energy with each step. But the spine can handle more intense forces when necessary, such as when a baggage handler lifts heavy pieces of luggage and heaves them into the belly of an aircraft.
Degenerative disc disease (DDD) is the deterioration of the discs in the spine. Usually the condition causes no problems, but in some people, it limits range of motion and produces chronic pain.
What is degenerative disc disease?
Each intervertebral disc (inter– means “between” and –vertebral refers, of course, to the vertebrae) is composed of a gelatinous central core, called the nucleus pulposus, surrounded by a tough, fibrous outer ring, called the annulus fibrosis (Figure 2).
As we age, the disc’s cellular composition changes and it becomes less able to absorb kinetic energy. Its gel-like nucleus loses water content, and collagen fibers in the outer ring weaken. The disc loses height and may bulge or herniate into the spinal canal, compressing nearby nerves and causing persistent back pain. Because branches of these nerves provide sensation to the arms and legs, pain from DDD can radiate down the leg or into the arm.
How common is lower-back pain associated with degenerative disc disease?
A recent study of almost 1,000 participants indicates that of those under age 50, 71% of men and 77% of women have DDD. It affects 90% of those age 65 and older.1
More women than men develop DDD. Smoking puts people at higher risk2, as does work that requires strenuous physical labor, particularly on the night shift.3 On the other hand, lack of participation in athletic activity is also a risk factor.4 Among young people, being overweight or obese is strongly associated with both presence and severity of DDD.5 Thankfully, most people with DDD have no symptoms.
What causes degenerative disc disease?
The precise cause of disc degeneration in any given person is usually unknown. Doctors used to think that age and overuse simply wore out the discs. Generations of coal miners, carpenters, cattle ranchers, and mechanics with bad backs provide plenty of anecdotal evidence that wear and tear does play some role in DDD. But researchers now believe that a genetic predisposition is the most important predictor of developing disc deterioration.6
As a disc ages, it’s subjected to continual biomechanical stressors. It dries out, becoming flatter and less flexible. Small tears and other irregularities further compromise the disc’s structure, and it becomes less able to absorb shock than when it was intact and healthy. With less support from the disc, nearby facet joints and vertebrae must pick up the slack. A damaged disc may also protrude into the spinal canal, crowding the space and impinging on nearby nerves.
What are the symptoms of degenerative disc disease?
DDD can affect the cervical spine (neck), thoracic spine (midback), or lumbar spine (lower back); however, thoracic disc disease usually doesn’t generate symptoms, since the middle portion of the spine is more stationary than the neck and lower-back areas. For many people, DDD produces no symptoms. Those who do have symptoms most often report back pain. DDD pain is a type of radiculopathy. Those with cervical DDD may have pain in the arm, neck, or shoulder. Pain in those with lumbar DDD may extend into the buttocks, leg, or foot.
How is degenerative disc disease diagnosed?
Your doctor will ask about your general medical history, including your medications and any past surgeries. He or she will ask you to characterize your pain—for instance, is it sharp, stabbing, or aching? Does it feel like an electric shock? The physician will want to know when the pain began, what (if anything) brought it on, whether it’s constant or intermittent, and which activities (such as walking) make it worse or better. The doctor will perform a thorough physical examination and may want to assess your gait (walking ability).
If at least 6 weeks of conservative treatment (see Treatment) is ineffective, he or she will probably also order a magnetic resonance imaging (MRI) scan of the spine.
To diagnose disc degeneration, a surgeon can inject a contrast dye into the body of the disc (see “What Is Degenerative Disc Disease” above). The dye allows him or her to visualize needle placement and gauge the health of the disc by assessing its size, shape, and anatomic integrity. About 0.5 to 2.5 mL of solution can be injected into a normal disk without causing pain. If the patient continues to have no pain response when a higher volume of solution is injected, it means the disc has a low water content, an indication of disease.7 If injection of more solution reproduces the patient’s pain, it shows that the pain originates at that level.
How is degenerative disc disease treated?
Treatment of DDD begins with physical therapy and nonopioid medications, progressing to prescription pain medication and other interventions as needed.
Physical therapy can strengthen the muscles that support the spine, relieving pressure on compromised discs, alleviating pain, and improving flexibility. Aquatic therapy is also a great way to relax the back, improve body mechanics, and tone back muscles. Modalities used to relieve the pain of DDD include massage, heat, ice, and electrical stimulation (see Transcutaneous Electrical Nerve Stimulation [TENS], below). Another option to improve posture and support the spine is bracing the back with a simple corset or a rigid plastic jacket.
Nonsteroidal anti-inflammatory drugs (NSAIDs), such as naproxen (Aleve) and ibuprofen (Advil), are the first line of defense in the medical treatment of DDD. Doctors also sometimes prescribe medications classified as anticonvulsants. These medications, such as gabapentin (Neurontin) block certain nerve pain signals in patients with DDD. Muscle relaxants can be useful, too, and antidepressants, antianxiety agents, and sleep aids can address the depression, stress, and sleeplessness often associated with degenerative disc conditions.
Opioid medications are prescription narcotic drugs that relieve pain. When prescribed sparingly by doctors and used responsibly by patients, they can be an effective adjunct to a patient’s pain management plan. If nonnarcotic medications and other conservative treatments haven’t worked for you, you and your doctor can discuss the risks and benefits of opioid therapy. In some patients, these medications can be administered by means of an implantable drug pump that automatically regulates dosage and administration.
Epidural injection of anesthetic or corticosteroid medications
To block transmission of pain signals and reduce inflammation in the spinal canal, your doctor can inject anesthetic medications or corticosteroids into the space surrounding the spinal cord (the epidural space).
Trigger point injections
The muscles surrounding the diseased disc or discs may be tender or tense. This tightness can be relieved by injecting anesthetics or corticosteroids at trigger points in affected muscles.
Transcutaneous electrical nerve stimulation (TENS)
A small battery-powered unit can deliver a low-voltage electrical current to painful muscles in the back. This sensation may trick the brain into focusing on the harmless electrical stimulation generated by the TENS unit, rather than on pain signals arising from the same area.
If pain persists despite conservative treatment for 6 months or longer, it may be time to consider surgery. All surgery involves risk, so discuss your options carefully with your doctor. Weigh the benefits and risks, such as damage to surrounding structures (which can be caused by open surgery techniques, see Minimally Invasive Spine Surgery Facts), bleeding, leakage of cerebrospinal fluid, infection, and poor healing.
Fortunately, serious complications are rare, and most patients have favorable outcomes. Only about 6% of patients require revision surgery within 7 years.8 And recent advances in medicine and technology, such as improved imaging quality, miniaturized surgical instrumentation, high-definition video, and innovative surgical techniques, have given DDD patients and their doctors even more options for decompression (surgical treatment).9
Cervical disc degeneration
Cervical decompression is often accomplished by removing a diseased disc, replacing it with an artificial one, and then fusing the spine with titanium hardware that remains permanently in place. This procedure is most often done by making an incision in the neck and retracting the trachea (moving it to the side) in order to reach the cervical disc space in question. For more information, see Inspired Spine’s minimally invasive Keyhole Surgery, anterior cervical discectomy and fusion (ACDF).
Many other surgical options are available, too, depending on what form of disc degeneration you have and where it’s located. For example, in some cases a laser can be used to cut out, aspirate (suck out), or destroy the core of a disc, which decreases pressure on the outer ring and adjacent nerve roots.10
Lumbar disc degeneration
Disc replacement in the lumbar spine relieves pain, maintains the joint space, and increases the strength and stability of the spine. Doing so used to require complicated, expensive, risky open surgery. Fortunately, newer procedures have made open surgery unnecessary in many patients with lumbar DDD at one or two vertebral levels. Keyhole surgery, such as the Inspired Spine oblique lumbar lateral fusion (OLLIF), requires only a small incision. Blood loss during the procedure is minimal, recovery is generally quick, and most patients enjoy excellent results.