Degenerative disc disease refers to the degeneration of at least one of the intervertebral discs of the spinal column. Some people may call it degenerative disc disorder.
Contents of this article:
What is degenerative disc disease?
Degenerative disc disease is a "disease of aging", an age related disease.
Over the years and decades, the repeated daily stresses on the spine and occasional minor, unnoticed injuries, as well as major ones, begin to take their toll.
For most people the gradual degeneration of the discs is not a problem. However, in some cases it eventually causes severe, chronic and debilitating discogenic pain. Back specialists refer to pain caused by a damaged intervertebral disc as "discogenic pain".
Some people have degenerative disc disease and never experience any related symptoms.
What are intervertebral discs?
Model of a healthy spine
The intervertebral discs (orange) act as cushions
between each vertebra (white)
Intervertebral discs, also known as intervertebral fibrocartilage or spinal discs, are the padding between each vertebra of the spine. They have an elastic structure, made of fibrocartilage tissue.
The outer part of the disc - annulus fibrosus - is tough and fibrous, and is composed of several overlapping layers.
The inner core of the disc - nucleus pulposus - is soft and gelatinous.
The intervertebral discs form the vertebrae's shock absorbers. They act as padding, and cushion the stress when the spine moves or bears weight.
These spinal discs also help the spine bend and then bend back to its normal curves.
In a healthy young adult the intervertebral discs consist of about 90% water. As we age the water content goes down, the padding becomes less thick and the spine becomes slightly shorter as a result. Sometimes the disc might bulge.
Signs and symptoms
A symptom is something the patient feels and describes, while a sign is something others can detect. Pain is an example of a symptom, and a rash is a an example of a sign.
Many people may have degeneration of the disc and have no symptoms. Others, on the other hand, may experience pain that is so intense that they are unable to carry out their daily activities.
Apart from pain, there may also be tingling and/or numbness in the leg or foot.
Most patients find that the pain is worse when they are sitting. This is because the discs have more weight on them when the body is sitting.
When specialist doctors talk about degenerative disc disease, they are usually referring to a combination of spinal problems that start with damage to the disc, and eventually spread to other parts of the spine.
The Mayfield Clinic2 in Cincinnati, Ohio, says that degenerative disc disease pain frequently starts in one of three ways:
- A major injury - which is followed by sudden and unexpected pain.
- A minor injury - which is also followed by sudden and unexpected back pain.
- Progressive pain - the patient starts feeling slight back pain, which over time gradually gets worse.
What causes degenerative disc disease?
As the human body ages, the intervertebral discs degenerate (break down), which leads to degenerative disc disease in some individuals.
The changes that occur, due to aging, include:
- Loss of fluid - the intervertebral discs of a healthy young adult consist mainly of fluid, up to 90%. As we age the disc's fluid content decreases, making it thinner. This means the distance between each vertebra becomes smaller.
Put simply, the cushion or shock-absorber between each vertebra becomes less effective.
- Disc structure is affected - very small tears or cracks develop in the annulus fibrous (outer layer) of the disc. The soft and gelatinous material in the nucleus pulposus (inner part of the disc) may make its way through the cracks or tears, resulting in a bulging or rupturing disc. Sometimes it may break into fragments.
This degeneration of the disc occurs more rapidly in obese individuals, people who do strenuous physical work, and regular tobacco smokers.
An acute (sudden) injury, as may occur after a fall, may accelerate the process of degeneration.
When the vertebrae have less padding between them the whole spine becomes less stable. The body tries to cope with this by building osteophytes, also called bone spurs. Bone spurs are small bony projections that develop along the edge of bones. These projections can press against the spinal cord or spinal nerve roots, which undermine nerve function and cause pain.
There is a condition called spinal stenosis, which occurs when the bone spurs grow into the spinal canal and press into the spinal cord and nerves.
Tests and diagnosis
The doctor will ask the patient about symptoms, where pain, tingling or numbness is felt and when, and which situations cause the most pain. Questions will also be asked about the patient's medical history and whether he or she had any falls, injuries or accidents.
The doctor will also carry out a physical examination, which may include:
- Checking nerve function - different areas are tapped with a reflex hammer. If there is poor or no reaction, it could mean there is a compressed nerve root.
Hot and cold stimuli may also be used to see how well the nerves sense temperature changes.
- Checking muscle strength - the patient may be asked to undress so the doctor can view the muscles and check for atrophy (wasting) or abnormal movements.
- Checking for pain with motion or palpation - palpation means examining or exploring by touching. The patient will also be made to move in specific ways. If pressure applied to the lower back causes pain, it could mean there is a degenerated disc.
The doctor may order the following diagnostic tests to either confirm a preliminary diagnosis, rule out some conditions or illnesses, or to gain more information:
- CT (computerized tomography) scan - a medical imaging method that employs tomography, the process of generating a 2-dimensional image of a section/slice through a 3-dimensional object (tomogram).
- MRI (magnetic resonance imaging) scan - a machine that uses a magnetic field and radio waves to create detailed images of the inside of the body on a monitor. MRIs scans give the doctor information on the state of the spinal nerves, discs and how they are aligned.
- Discogram - a dye is injected into the nucleus pulposus, the soft center of the disc. Sometimes several disks are injected. The aim is to see whether the disc is painful. The dye shows up on a CT scan or X-ray. According to the Mayo Clinic3, discogram usage is controversial because cracked discs do not always cause symptoms.
- Kneeling or reclining - rather than sitting is less painful. Patients can be taught how to position themselves so that their symptoms are less severe.
- Lifting weights - this needs to be done without bending the body.
- Medications - the patient may benefit from non-steroidal anti-inflammatory drugs (NSAIDs), steroids and sometimes muscle relaxers.
Examples of NSAIDs include celecoxib, ibuprofen, naproxen and aspirin.
Acetaminophen (paracetamol, Tylenol) is a painkiller but not an anti-inflammatory.
Steroids may help reduce swelling and inflammation around the nerves.
- Wearing a corset or brace
- Doing special exercises to build the back and stomach muscles - according to UCLA Neurosurgery4, yoga, Pilates, and swimming are effective, as are some other core strengthening programs.
- Specialized health care professionals, such as physiatrists, neuroradiologists and pain management specialists can help with more aggressive treatments that do not require surgery.
The joints next to the bad disc can be injected with steroids and a local anesthetic. These are called facet joint injections and can provide effective pain relief.
- Facet rhizotomy - a radiofrequency current deadens the nerves around the facet joint, preventing pain signals from reaching the brain. This may be recommended if the patient responded to facet joint injections. Facet rhizotomy may provide pain relief that lasts for more than a year.
- Intradiscal electrothermal annuloplasty (IDET) - painful discs are heated up using discography CT with a copper coil; when the right temperature is reached the disc hardens, making it better at resisting weight-bearing movements. According to UCLA Neurosurgery, this procedure is effective in 70% of cases.
Surgery may be recommended if the patient did not respond to conservative therapies within about three months.
Surgery may be considered as an option if:
- Back or leg pain stops the patient from going about normal activity.
- There is numbness in the legs.
- There is weakness in the legs.
- Standing or walking is difficult.
- The patient did not respond to physical therapy.
- Medication was not effective.
The following surgical options are available:
- Stabilization surgery - spinal fusion - two vertebrae of the spine are fused together. This provides stability for the spine. The procedure can be done at any level of the spine, but is more common in the lower back area (lumbar region) and the neck area (cervical region) - these are the most movable parts of the spine.
Spinal fusion can be done from the back, with rods and screws in the spine and adjacent bone graft. If done from the front, the disc is removed and graph materials are placed.
This procedure is very effective for patients in extreme pain whose spine cannot bear their own weight. However, spinal fusion can speed up the degeneration of the discs next to the fused vertebrae.
- Decompression surgery - examples include facectomy (removing the facet joint), foraminotomy (enlarging the opening of the foramen so the nerve is not compressed), laminectomy (removing all or part of the lamina to relieve pressure on the spinal cord), laminotomy (like a laminectomy, but the opening is larger, giving the nerves more room).
In the decompression procedures described above, the surgeon comes in from the back of the spine. Sometimes decompression surgery has to be done from the front (anterior), as may occur if the patient has a bulging disc or herniated disc that pushes into the spinal canal.
Anterior decompression techniques include discectomy (removal of all or part of the disc), corpectomy (the vertebral bodies and adjacent discs are removed in order to reduce the pressure on the spinal cord).
Stem cell therapy
Researchers at the University of Queensland, Australia, set out to determine whether a tissue engineering-based approach using stem cells, coupled with an advanced delivery system might encourage functional fibrocartilage generation.
The scientists developed an injectable hydrogel system based on enzymatically-crosslinked polyethylene glycol (gel) and hyaluronic acid.
After adding more substances to the hydrogel they injected it into patients. Their aim was to induce chondrogenesis (formation of cartilage) in mesnchymal precursor cells.
The researchers concluded in the journal Biomaterials5 that stem cell therapy has potential for intervertebral disc regeneration.