Lumbar Disc Protrusion

A herniated disc is a condition that can occur anywhere along the spine, but most often occurs in the lower back (lumbar spine). It is sometimes called a bulging, protruding, or ruptured disc. It is one of the most common causes of lower back pain, as well as leg pain (or “sciatica”). About 60% and 80% of people will experience low back pain at some point in their lives, which may be caused by a herniated disc. Although a herniated disc can be very painful, most people feel much better with just a few weeks or months of nonsurgical treatment.

Anatomy

The spine is made up of 24 bones, called vertebrae, that are stacked on top of one another, and they connect to create a canal that protects the spinal cord. Five vertebrae make up the lower back, known as the lumbar spine.

Other parts of your spine include:

• Spinal cord and nerves - These "electrical cables" travel through the spinal canal carrying messages between your brain, muscles and other structures. Nerve roots branch out from the spinal cord through openings between the vertebrae called nerve foramens.
• Intervertebral discs - In between the vertebrae are flexible intervertebral discs, which are flat and rounded, and about 5-10mm thick. The discs act as shock absorbers when you walk or run. They are made up of two components:
• Annulus fibrosus - A tough, flexible outer ring of the disc.
• Nucleus pulposus - The soft, jelly-like centre of the disc.

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Parts of the lumbar (lower) spine.

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Healthy intervertebral disk (cross-section view).

Description

A disc begins to herniate when its jelly-like nucleus pushes against its outer ring due to wear and tear or a sudden injury. This pressure against the outer ring may cause lower back pain. 

If the pressure continues, the jelly-like nucleus may push all the way through the outer ring or cause the ring to bulge. This puts pressure on the adjacent spinal cord and nearby nerve roots. In addition, the disc material releases chemical irritants that contribute to nerve inflammation. When a nerve root is irritated, there may be pain, numbness, and weakness in one or both of your legs, a condition known as “sciatica.”

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In a herniated disc, the soft, jelly-like centre of the disc can push all the way through the outer ring.  (Cross-section and side views shown.)

Cause

A herniated disc is most often the result of natural, age-related wear and tear on the spine, a process called disc degeneration. In children and young adults, discs have high water content, but as people age, the water content in the discs decreases and the discs can become less flexible. The discs begin to shrink and the spaces between the vertebrae get narrower. This normal aging process makes the discs more prone to herniation. A traumatic event, such as a fall, can also cause a herniated disc.

Risk Factors

Certain factors may increase your risk of a herniated disc, including:

• Gender - Men aged 20-50 are most likely to have a herniated disc.
• Improper lifting - Using your back muscles instead of your legs to lift heavy objects can cause a herniated disc. Twisting while you lift can also make your back more vulnerable. 
• Weight - Being overweight puts added stress on the discs in your lower back.
• Repetitive activities that strain your spine - Many jobs are physically demanding. Some require constant lifting, pulling, bending, or twisting. Using safe lifting and movement techniques can help protect your back.
• Frequent driving - Staying seated for long periods, plus the vibration from the car engine, can put pressure on your lumbar spine and discs.
• Sedentary lifestyle - Regular exercise is important in preventing many medical conditions, including a herniated disc.
• Smoking - It is believed that smoking lessens the oxygen supply to the disc and causes more rapid degeneration.

Symptoms

In most cases, low back pain is the first symptom of a herniated disc. This pain may last for a few days, then improve. Other symptoms may include:

• Sciatica - This is a sharp, often shooting pain that extends from the buttock down the back of one (or both) leg, caused by pressure on the spinal nerve.
• Numbness or a tingling sensation in the leg and/or foot
• Weakness in the leg and/or foot
• Loss of bladder or bowel control - This is extremely rare and may indicate a more serious problem called cauda equina syndrome. This condition is caused by the spinal nerve roots being compressed. It requires immediate medical attention.

Diagnosis and Investigations

Medical History and Physical Examination

After discussing your symptoms and medical history, a physical examination will be performed. The exam may include the following tests:

• Neurological examination - This will help determine if you have any muscle weakness or loss of sensation, and includes:
  • Check muscle strength in your lower leg
  • Detecting loss or altered sensation 
  • Test of the reflexes at the knee and ankle.
• Straight leg raise (SLR) test - This test is an accurate predictor of a disc herniation in patients under the age of 35. During the test, you lie on your back and your affected leg is lifted with the knee straight. If you feel pain down your leg and below the knee, it is a strong indication that you have a herniated disc.

Imaging Studies

Xrays – These may include functional flexion and extension views.  If there is a suggestion of referred pain from adjacent areas, such as the pelvis/sacroiliac region, Xrays of these areas may be included.

Magnetic resonance imaging (MRI) scans - These studies provide clear images of the body’s soft tissues, including intervertebral discs. 

If you are unable to tolerate an MRI (perhaps due to claustrophobia, a computerized tomography (CT) scan, or a CT myelogram may be ordered instead.

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MRI scan shows a herniated disc in the lower back (arrow). The disc is bulging back into the spinal canal, putting pressure on the spinal cord and nerve roots, with adjacent endplate oedema (the white blush above and below the disc in the vertebrae).

Treatment

For the majority of patients, a herniated lumbar disc will slowly improve over a period of several days to weeks. Typically, most patients are free of symptoms by 3 to 4 months.

Nonsurgical Treatment

Initial treatment for a herniated disc is usually nonsurgical in nature, with a focus on providing pain relief. Nonsurgical treatments may include:

• Rest - One to 2 days of bed rest will usually help relieve back and leg pain. When you resume activity, try to do the following:
• Take rest breaks throughout the day, but avoid sitting for long periods.
• Make all your physical activity slow and controlled, especially bending forward and lifting.
• Change your daily activities to avoid movements that can cause further pain.
• Nonsteroidal anti-inflammatory medications (NSAIDs) can help relieve pain.
• Physical therapy -Specific exercises will help strengthen your lower back and abdominal/core muscles.
• Epidural steroid injection - An injection of a cortisone-like drug into the space around the nerve may provide short-term pain relief by reducing inflammation. There is good evidence that epidural injections can successfully relieve pain in many patients who have not been helped by 6 weeks or more of other nonsurgical care.

Surgical Treatment

Only a small percentage of patients with lumbar disc herniation require surgery. Those patient’s with MRI evidence of an acute annular tear are more likely to require earlier surgery. Spine surgery is typically recommended only after a period of nonsurgical treatment has not relieved painful symptoms, or for patients who are experiencing the following symptoms:

• Muscle weakness
• Difficulty walking
• Loss of bladder or bowel control

Microdiscectomy – This is the most common procedure used to treat a single herniated disc, and is done through a small incision at the level of the disc herniation (confirmed with intra-operative Xray imaging). The herniated part of the disc is removed along with any additional fragments that are putting pressure on the spinal nerve. A larger procedure may be required if there are disc herniations at more than one level.

Rehabilitation - A simple walking program (such as 30 minutes each day) is recommended, along with specific exercises to help restore strength and flexibility to your back and legs. Hydrotherapy is also useful in the early stages (as long as the wound is sealed with a waterproof dressing). To reduce the risk of repeat herniation, you may be prohibited from bending, lifting, and twisting for the first few weeks after surgery, and sitting should be limited to 30 minutes three times per day in the first 2-4 weeks.  Driving is also not recommended for 4-6 weeks.

Considerations

With both surgical and nonsurgical treatment, there is a 10-12% chance that the disc will herniate again.

The risk of nonsurgical treatment is that your symptoms may take a long time to resolve. Patients who try nonsurgical treatment for too long before electing to have surgery may experience less improvement of pain and function than those who elect to have surgery earlier. 

Surgical risks - There are minor risks associated with every surgical procedure, and include bleeding, infection, and reaction to anaesthesia. 

Specific complications from surgery for a herniated disc include:

• Nerve injury
• Infection
• Tear of the sac covering the nerves (dural tear)
• Hematoma causing nerve compression
• Recurrent disc herniation
• Need for further surgery

Outcomes

Overall, the results of microdiscectomy surgery are generally very good. Patients tend to see more improvement of leg pain than back pain. Most patients are able to resume their normal activities after a period of recovery following surgery. Typically, the first symptom to improve is pain, followed by overall strength of the leg, and then sensation (once the pressure is relieved from the nerve, the nerve “regenerates” at about 1mm per day – improvements or full return may not occur for more than 12-24 months).