Spinal discs naturally degenerate with age due to wear-and-tear, but this doesn’t always lead to pain or other symptoms. Degenerative disc disease (DDD) is a condition (not actually a disease) in which degenerated discs cause pain and/or other symptoms that cannot be explained by any other condition. DDD is a leading cause of back pain.
The symptoms of DDD will depend on the location of the degenerated disc(s) within the spine and any secondary effects of disc degeneration.
Symptoms of DDD may include:
- Pain in the lower back;
- Pain in the buttocks;
- Pain radiating down the leg (such as sciatica – caused by irritation of a spinal nerve);
- Pain in the neck that may spread to the arms;
- Pain that is worse when sitting;
- Pain that is relieved when lying down;
- Reduced range of motion of the spine;
- Numbness or paraesthesia (pins-and-needles / tingling sensation) in limbs;
- Weakness in legs or feet;
- Difficulty with walking and/or balance;
- Impaired hand function;
- Electric-shock-like sensations along the spine or limbs;
- Issues with bladder, bowel or sexual function.
Diagnosis of DDD begins with a review of the patient’s history, a physical examination, and a review of treatment history – i.e. how the patient responded to medications and non-surgical treatments for their symptoms. The doctor may request diagnostic medical imaging. A diagnostic procedure known as discography may also be performed.
An X-ray, CT scan, or MRI of the spine may help with diagnosis of DDD. X-rays are used to check bone structure and alignment of the spine. A CT scan may be used to check the spinal canal, and can show calcification (thickening/hardening) of spinal ligaments, and bony growths/spurs known as osteophytes. MRI is much better at imaging the actual disc, as well as the spinal cord and spinal nerves. MRI can show disc dehydration and possible inflammation.
A provocative discography is a specialised tool to diagnose DDD in patients with symptoms, who have not responded to other treatments, and where medical imaging has ruled out any other possible causes. It is a procedure that involves injecting a small amount of radiopaque dye into the suspected disc(s). The dye allows for disc abnormalities to be viewed under X-ray, and can also detect painful discs. If the patient reports pain when a disc is injected, the doctor can suspect that disc.
(Image by BruceBlaus [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)])
What Causes DDD?
Spinal discs are cartilage structures that sit between the bones (vertebrae) of the spine. Similar to ligaments and joints, they hold the vertebrae together, allow for some movement in the spine, and act as shock-absorbers. Inside a disc is a soft, gel core (the nucleus pulposus), which contains up to 80% water. The exterior of a disc (the annulus fibrosus) is tough and made up of layers of collagen fibres.
(Image by OpenStax College [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)])
As mentioned earlier, the discs naturally degenerate with age and general wear-and-tear, but this does not always lead to DDD. Over time, discs slowly lose water, causing them to shrink and stiffen. Dehydration of a disc is known as desiccation – this is one of the most common signs of DDD.
Annular tears or changes in the collagen outer layers of the disc may also occur with ageing, or with injury or mechanical stress on the discs, which can also lead to DDD.
Inflammation of the disc can also lead to DDD. Degenerated discs may release inflammatory factors that can amplify the inflammatory response and cause the disc to become more sensitive and generate pain.
Known risk factors for DDD include:
- Older age;
- Injury to the spine;
- Mechanical stress (i.e. heavy lifting);
- Occupation (i.e. labour-intensive jobs, sports, military);
- Family history of a musculoskeletal disorder;
- Weak core muscles (lack of spine support);
DDD can lead to further issues that cause additional or worsened symptoms. These include:
- Bulging disc – the disc bulges out the side(s);
- Herniated disc – a more extreme case of bulging disc, also known as a slipped or ruptured disc, where the inside of the disc (nucleus pulposus) pushes out through a tear in the outer layer and can push against a nearby nerve and cause pain;
- Scoliosis – abnormal sideways curving of the spine;
- Spinal stenosis – narrowing of the spinal column, which can lead to pinching of the spinal cord or nerve roots and cause pain;
- Spondylosis – osteoarthritis of the spine due to osteophytes (shown in the picture on the right);
- Spondylolisthesis – a slipped vertebrae due to degeneration of a facet joint (the joint between the bony projections at the back of the vertebrae);
- Cauda equina syndrome – compression of the nerve bundles located at the bottom of the spinal cord, affecting muscles controlling the bowel, bladder and genitals.
Current Treatment Options
For most patients, conservative, non-surgical treatments are tried first. These include the following.
Physical therapy under the guidance of a physical therapist is highly recommended. The aims of physical therapy include:
- Strengthening core muscles to improve spine support;
- Increasing muscle flexibility;
- Increasing blood flow to improve delivery of oxygen and nutrients to the discs, and to help cleanse the disc/joint of any inflammation by-products.
- Non-steroidal anti-inflammatory drugs (NSAIDs) may help to relieve pain and swelling associated with inflammation (i.e. ibuprofen, naproxen, celecoxib);
- Analgesics (i.e. paracetamol) for basic pain relief;
- Short term use of oral steroids for pain and inflammation;
- Muscle relaxants.
- Epidural steroid injection (i.e. into the epidural space surrounding the spinal cord) for short-term pain relief;
- Cognitive behavioural therapy (CBT) is recommended in some patients.
For patients that don’t respond to the above, or who have severe symptoms such as cauda equina syndrome, spinal surgery may be recommended, such as:
- Spinal fusion – removal of the disc and permanent joining of the vertebrae;
- Total disc replacement (arthroplasty) with a prosthetic disc that provides the same degree of spinal movement as a normal disc would.
Lifestyle changes can help to slow down disc degeneration or prevent DDD, for example:
- Increasing physical activity;
- Healthy diet;
- Healthy weight;
- Stop smoking.
Ongoing research aims to discover and develop methods to prevent disc degeneration or restore degenerated discs. One of the most promising ways by which this might be achieved is with cell and tissue engineering. The aim of cell/tissue engineering is to regenerate disc tissue and therefore reverse the degeneration process or restore the function of a degenerated disc. Strategies to restore degenerated discs that are being researched include the following:
- Stem cell therapy – stem cells are harvested from the body (e.g. from the bone marrow), grown in the laboratory and transplanted into the disc.
- Injection of harvested cartilage cells (chondrocytes) into the disc.
- A hydrogel is a highly absorbent gel made up of a network of long molecule chains.
- Hydrogels act as biological “scaffolds”, which provide a suitable environment for cells to occupy and generate disc tissues.
- Collagen hydrogels that contain stem cells can be injected into the nucleus pulposus of degenerated discs and have been shown to restore the height of discs and promote new cell development.
- GFs are proteins present in the body that stimulate tissue growth.
- GFs that may enhance disc tissue regeneration include:
- Growth and differentiation factor 5 (GDF-5) – in clinical trials;
- Insulin-like growth factor (IGF-1);
- Bone morphogenetic protein 2 and 7 (BMP-2, BMP-7);
- Platelet-derived growth factor (PDGF);
- Transforming growth factor beta-1 and -3 (TGF-ß1, TGF-ß3).
- Gene therapy – genes that that might be able to help treat DDD can delivered to the disc where they become incorporated into the DNA of disc cells.
- Platelet-rich plasma (PRP) injections – PRP is extracted from the patient’s own blood and injected into the disc. PRP contains growth factors and other molecules or proteins that may help inflammation, wound-healing and stimulate regeneration.
Genesis Research Services conducts clinical trials for a range of painful conditions, including DDD. To view currently recruiting studies, or register your interest for future studies, click here or call us on (02) 4985 1860.
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