What is a disc?
The disc is a soft tissue, elastic structure called a spinal disc, or intervertebral disc. It lies between each vertebral body. There is a naming system used based on which level the disc is located for example L12 disc means that it is located between the first and second lumbar vertebra.
What is the structure of the disc?
The intervertebral discs are composed of an annulus fibrosus and a nucleus pulposus.
The annulus fibrosus is a strong radial tire–like structure made up of lamellae; concentric sheets of collagen fibers connected to the vertebral end plates. The sheets are orientated at various angles. The annulus fibrosus encloses the nucleus pulposus.
Although both the annulus fibrosus and nucleus pulposus are composed of water, collagen, and proteoglycans (PGs), the amount of fluid (water and PGs) is greatest in the nucleus pulposus.
PG molecules are important because they attract and retain water. The nucleus pulposus contains a hydrated gel–like matter that resists compression. A healthy disc in a young adult consists of approximately 90% water. The amount of water in the nucleus varies throughout the day depending on activity.
What is the function of the discs?
The intervertebral discs are fibrocartilaginous cushions serving as the spine's shock absorbing system, which protect the vertebrae, brain, and other structures (i.e. nerves). The discs allow some vertebral motion: extension and flexion. Individual disc movement is very limited – however considerable motion is possible when several discs combine forces.
Together, the disc forms a hydraulic "shock absorber", able to cushion the stress during movement of the spine. The intervertebral discs help the spine return to and keep its normal curves following any spinal movement.
Why is the disc prone to damage?
Discs are not vascular and therefore depend on the end plates to diffuse needed nutrients. The cartilaginous layers of the end plates anchor the discs in place. As one ages these pores get blocked off and no nutrition goes to the disc. This is the reason they do not heal when a tear occurs.
What is the cause of disc damage?
There is an interplay between genetic and environmental factors.
What Is Degenerative Disc Disease (DDD)?
Degenerative disc disease (DDD) is part of the natural process of growing older. As we age, our intervertebral discs lose their flexibility, elasticity, and shock absorbing characteristics. The outer fibers that surround the disc, called the annulus fibrosis, become brittle and are more easily torn. At the same time, the soft gel-like center of the disc, called the nucleus pulposus, starts to dry out and shrink. The combination of damage to the intervertebral discs, the development of bone spurs and the gradual thickening of the ligaments that support the spine can all contribute to degenerative arthritis of the lumbar spine.
To a certain degree, this process happens to everyone. However, not everyone who has degenerative changes in their lumbar spine has pain. Many people who have "normal" backs have MRIs that show disc herniations, degenerative changes, and narrowed spinal canals. Every patient is different, and it is important to realize that not everyone develops symptoms as a result of degenerative disc disease.
What Are The Symptoms Of Degenerative Disc Disease?
When degenerative disc disease becomes painful or symptomatic, it can cause several different symptoms due to the compression of the nerve roots. Depending on where your degenerative disc is located, it could cause
These symptoms are caused by the fact that worn out discs are a source of pain because they do not function as well as they once did, and as they shrink, the space available for the nerve roots also shrinks. As the discs between the intervertebral bodies start to wear out, the entire lumbar spine becomes less flexible. The result can be back pain and stiffness, especially towards the end of the day.
How Is Degenerative Disc Disease Diagnosed?
The diagnosis of degenerative disc disease begins with a complete physical examination. Your doctor will examine your back for flexibility, range of motion, and the presence of certain signs that suggest your nerve roots are being affected by degenerative changes in your back. This often involves testing the strength of your muscles and your reflexes to make sure that they are still working normally. You will often be asked to fill out a diagram that asks you where your symptoms of pain, numbness, tingling and weakness are occurring.
A series of x-rays is also usually ordered for a patient with back pain. If degenerative disc disease is present, the x-rays will often show a narrowing of the spaces between the vertebral bodies, which indicates the disc has become very thin or has collapsed. Bone spurs also can form around the edges of the vertebral bodies and also around the edges of the facet joints in the spine. These bone spurs can be seen on an x-ray, and are also called osteophytes. As the disc collapses and bone spurs form, the space available for the nerve roots starts to shrink. The nerve roots exit the spinal canal through a bony tunnel called the neural foramen, and it is at this point that the nerve roots are especially vulnerable to compression.
In many situations, doctors will order a MRI or a CT scan (CAT scan) to evaluate the degenerative changes in the lumbar spine more completely. A MRI is very useful for determining where disc herniations have occurred and where the nerve roots are being compressed. A CT scan is often used to evaluate the bony anatomy in the spine, which can show how much space is available for the nerve roots and within the neural foramina and spinal canal.
How Is Degenerative Disc Disease Treated?
Your doctor will discuss with you the treatment options appropriate for your diagnosis.
For most people who do not have evidence of nerve root compression with muscle weakness, conservative, non-surgical therapies, such as medication, rest, exercise and physical therapy, are typically recommended.
Surgery is offered only after conservative treatment has have failed to adequately relieve the symptoms of pain, numbness and weakness over a significant period of time.
What is a herniated disc?
A herniated disc, also called a bulging disc, ruptured disc or slipped disc, occurs when the inner core of the spinal disc pushes out through the outer layer of the disc.
Herniation describes an abnormality of the intervertebral disc that is also known as a "slipped," "ruptured" or "bulging" disc. This process occurs when the inner core (nucleus pulposus) of the intervertebral disc bulges out through the outer layer of ligaments that surround the disc (annulus fibrosis). This tear in the annulus fibrosis causes pain in the back at the point of herniation. If the protruding disc presses on a spinal nerve, the pain may spread to the area of the body that is served by that nerve.
What Are The Symptoms Of A Herniated Disc?
Usually, the main symptom is sharp, acute pain. In some cases, there may be a previous history of localized low back pain, with pain also extending down the leg served by the affected nerve. This pain is usually described as a deep, sharp pain, which gets worse as it moves down the affected leg. The onset of pain with a herniated disc may occur suddenly or it may be preceded by a tearing or snapping sensation in the spine, which may be attributed to a sudden rupture in the annulus fibrosis.
How Is A Herniated Disc Diagnosed?
A patient with a herniated disc will usually complain of low back pain that may or may not radiate into different parts of the body, such as the leg. They will often demonstrate a limitation in range of motion when asked to bend forward or lean backwards, and they may lean to one side as they try to bend forward. Patients will sometimes walk with a painful gait, flexing the affected leg so as not to put too much weight on the side of the body that hurts. Straight leg raising may be a positive indication of tension on the nerve root.
Abnormalities in the strength and sensation of particular parts of the body that are found with a neurological examination performed by a doctor provide the most objective evidence of nerve root compression. An MRI is the test of choice for diagnosis of a herniated disc, but a CT scan (CAT scan) also may be helpful because it provides better visualization of the bony anatomy of the spinal column that indicates where the source of pressure on the nerve root is located.
How Is A Herniated Disc Treated?
Treatment for the vast majority of patients with a herniated disc does not normally include surgery. Most patients will respond to conservative therapy, such as medication, rest and physical therapy.
The primary element of conservative treatment is controlled physical activity. Usually treatment will begin with a modification of activity and then a gradual return to protected activities. Sitting, bending, lifting and twisting are not beneficial for this condition because they put a large amount of stress and pressure on the lumbar spine, which may increase the pressure on the affected nerve root. The appropriate use of medication is an important part of conservative treatment. This can include anti-inflammatory drugs, analgesics and muscle relaxants.An anti-inflammatory spinal injection for the area of the affected nerve root to lessen swelling and irritation caused by the damaged disc.
Surgery is typically recommended only after physical therapy, rest, and medications have failed to adequately relieve the symptoms of pain, numbness and weakness over a significant period of time.
The benefits of spine surgery, however, must be weighed against the risks. Your surgeon will be able to discuss the risks and benefits of surgery with you, and the likely results of operative versus non-operative treatment.