Lumbar Disc Herniation

Overview

Discs are the pads between the vertebrae of the spine. There are twenty-four mobile vertebrae and five that are fused together to form the sacrum. Discs are vulnerable to injury because they have the difficult job of being flexible enough to move, but strong enough to take enormous stress.

The discs between the lower lumbar vertebrae are the most commonly injured because they support the weight of the entire upper body. The structure of the disc determines the extent of injury, if one occurs.

Disc herniation, rupture, protrusion, and extrusion are all terms that describe this injury. There are subtle differences between these terms, but they all refer to a tear in the outer ring, which allows some of the inner core to escape. A herniation occurs when a portion of the soft inner core (nucleus pulposis) escapes through the outer ring (annulus).

The disc may look like a solid piece of padding between the vertebrae, but it is far more complex. Discs are composed of two parts that work together to carry the load.

  • The strong outer ring or annulus, is firmly attached to the vertebrae above and below the disc. The ring has strong crosshatched fibers much like the steel belts of a car tire. This outer ring is about 1/4 inch thick, and by itself, doesn't have much compressive strength. If this ring were empty, it would collapse when weight was applied to the bone above. The outer ring holds the nucleus pulposis in place.
  • The nucleus pulposis is located inside the annulus. This is a soft gelatin-like cartilage with a very high water content which provides cushioning while evenly supporting the weight of the body. This cartilage transmits the load from bone to bone.

There is a delicate balance between the forces trying to push the gelatin-like nucleus out to the sides and the tension of the outer ring holding it in place.

The disc has two functions:

  • it transmits the weight of the body from the bone above to the bone below.
  • it allows the spine to be flexible.

The lumbar (lower back) discs must support the weight of the entire upper body plus whatever is picked up or carried. Because the body's center of gravity is in front of the discs, loads on the disc are increased by leverage, much like a nutcracker multiplies force on a nut. Research has shown that picking up a 20 pound weight may increase pressures inside the disc by more than eight times the body's weight. The job of the disc is to transmit this load efficiently and evenly to the vertebra below. The gelatin-like nucleus pulposis distributes the stress evenly across the surfaces of the adjacent bones. The combination of soft inner core and strong outer ring also allows maximum motion between the bone segments. Both of these functions are severely tested in the lumbar spine, where enormous loads frequently occur and physical activities demand wide ranges of motion.

What is a herniated lumbar disc?

The outer ring of the disc is subject to continuous stresses that sometimes cause small tears to develop. If one of these tears is large enough and the stresses inside the disc strong enough, some of the pulposis can leak through the tear. The disc is most vulnerable to injury at the weakest parts of the outer ring, where nerves pass through the spinal canal and exit toward the legs. If disc material compresses one of these nerves, there can be pain both in the back and down the leg . Pain down the leg is often called sciatica,because the most frequently pinched nerves form the sciatic nerve, which runs down the back of the thigh to the lower leg.

A disc can herniate due to either a sudden load or an accumulation of minor injuries over time. At least 50% of patients can't recall a specific event that caused the ruptured disc. When an event can be identified, it often involved lifting and twisting; activities that place severe stresses on the disc.

Discs are named for the bones above and below them. For example, the L4-5 disc is between the 4th and 5th lumbar bones. The L5-S1 disc is between the 5th lumbar and 1st sacral bones. These two discs do the most work and are the most frequently injured. Paralysis rarely occurs with disc herniation. The spinal cord proper ends at the first lumbar vertebra (L1), well above these frequently injured discs.

Other conditions that cause back and leg pain can mimic a ruptured lumbar disc. Some of these conditions are:

  • arthritis of the hip or knee area.
  • pulled muscles in the back (lumbar strain).
  • pulled muscles in the leg and other conditions that cause irritation of the spinal nerves.

What are the signs and symptoms of a herniated disc?

People with common herniated lumbar discs experience some combination of back and leg pain such as numbness, tingling, and/ or weakness along the compressed nerve. At first, most people experience severe back pain in conjunction with muscle spasm. Because these are also symptoms of pulled back muscles, at first it is difficult to distingush between a ruptured disc and a lumbar strain.

After a few days, the back pain usually subsides, and pain in one leg takes over. This pain is often described as an "electric shock", or burning sensation, that follows the nerve from the buttock, down the back of the thigh and into the calf or foot. This type of pain is called sciatica for the sciatic nerve that runs in the same area.

  • There may be numbness, tingling, or a "pins and needles" feeling as well as other abnormal sensations along the pinched nerve.
  • The muscles controlled by the nerve may weaken because they are not getting normal signals from the brain and spinal cord. Eventually, these muscles may atrophy (become smaller) because they are not being used.
  • Although these are the most common symptoms, there may be any combination of back and leg pain in varying degrees of severity, from a very mild ache to unbearable pain requiring a visit to a hospital emergency room.

The most dangerous ruptured disc compresses all the nerves passing through the lower back, including those that control bladder and bowel function. These nerves are well protected so this situation is rare. However, when it does happen, it is a true emergency that requires immediate surgery. Symptoms include:

  • an inability to control urine or stool functions.
  • an inability to urinate at all.
  • numbness around the rectum, buttocks and genital area.

How is a herniated lumbar disc diagnosed?

The physician will use a combination of history (patient interview), physical examination, and imaging (Xray, MRI, CT scan, etc.) to make a diagnosis of herniated disc.

The history is the information the patient gives the physician about the injury. The doctor will want to know:

  • how the pain began, how long it has been going on,and how severe it is.
  • if an accident or fall preceded the pain.
  • The the state of the patient's general health.
  • which medications the patient is taking (both prescription and over the counter).
  • other treatments that have been tried and whether any of them have been helpful.

The doctor will check several functions in the physical examination:

  • Gait: The doctor may ask the patient to walk normally, then walk on heels and finally on toes to check balance, as well as perform other maneuvers.
  • Range of motion: The patient may be asked to bend over and lean backwards and sideways to examine the mobility of the back.
  • Back examination: The back will be checked for curvatures, muscle spasm, and tenderness.
  • Examination of the legs: Other conditions such as hip problems, leg length differences, circulation problems and injuries to the legs must be checked.
  • Nerve root tension signs: The doctor may stretch the legs in various ways to see if stretching a nerve will reproduce the pain. This helps determine if a nerve is compressed. The most common of these tests is the "straight leg raise".
  • Neurologic examination: The doctor will evaluate as many nerve functions as possible in the patient's legs. This will include checking the sense of touch using a pin prick and evaluating the strength in several leg muscles. The reflexes at the knee and ankle will also be tested.

It is often necessary to obtain an X-ray, MRI, bone scan, or myelogram. Since many people recover completely in a short time, most doctors suggest waiting until the condition has failed to respond to several weeks of conservative (non-operative) treatment before getting imaging studies.

  • X-rays: The most common imaging study is the X-ray, which is best suited for looking at the bones. Fractures, disc degeneration, arthritis and spinal deformities are also visible on regular X-rays. Abnormal movements of the vertebrae can be identified if X-rays are made while the patient is bending forward or leaning backward.
  • Computed Tomography (CT scan): This is a special type of X-ray that shows soft tissues (disc, nerve, muscle and ligament) more clearly than a regular X-ray. CT scans are about 83% accurate at diagnosing a herniated disc.
  • MRI (Magnetic Resonance Imaging): The MRI is ordered only after a period of unsuccessful conservative treatment. The MRI is extremely good at showing the discs, nerves, spinal cord, spinal fluid, muscles and ligaments. It is about 93% accurate at finding herniated discs.
  • Myelogram and Post Myelogram CT Scan: During a myelogram the radiologist injects dye into the spinal fluid. A series of X-rays is followed by a CT scan. The dye outlines the nerves and makes them easier to see. This method is also about 93% accurate at identifying herniated discs, but most doctors prefer an MRI because it does not require an injection. A myelogram and post myelograin CT scan is often done when an earlier MRI was not conclusive.

How is a herniated lumbar disc treated?

Non-operative treatment for the first 4-6 weeks:
Except in a few special circumstances, initial treatment for herniated discs should be conservative. People with back pain and sciatica are treated alike, with emphasis on pain relief and early mobilization. Fortunately, herniated discs improve without surgery about 80% of the time. It usually takes four to six weeks of conservative treatment before a patient can resume normal activities. One research study investigated the results of conservative versus operative treatment for herniated discs. It showed that surgical patients did better when checked at 1, 2 and 4 years. After ten years, however, the two groups were doing equally well, indicating that eventually the pain associated with herniated discs resolves on its own.

  • Narcotic pain medicines: If the first few days are extremely painful, narcotic pain medicines are often prescribed. Some of these are safe for short periods, but have worrisome side effects when used for a long period of time.
  • Anti-inflammatory medicines: Since inflammation of the spinal nerves and back muscles contribute to the problem, anti-inflammatory medicines are frequently prescribed. These are often called "arthritis medicines" or "NSAIDs" (non steroidal anti inflamatory drugs) It usually takes several days of treatment before NSAIDs are fully effective. Some NSAIDs may cause acid stomach so they should generally be taken with food.
  • Muscle relaxers: These medicines are given to help ease muscle spasm. Their usefulness is controversial, and they tend to make patients drowsy.
  • Oral corticosteroids: These powerful anti-inflamatories have many side effects so their use is limited. The side effects of upset stomach, mood swings and changes to the endocrine system are minimized if the length of treatment is limited to a week. These medicines are often given in tapering doses daily for 7 to 10 days and then stopped.
  • Physical therapy: Physical therapists have several treatments that can help loosen cramped muscles and ease pain. One very important contribution they make is to get the patient started on a specific exercise program to strengthen the stomach and back muscles after the initial spasms have subsided. An ongoing commitment to a home exercise program is the best way to protect against a recurrence of back problems.

Non-operative treatment after the first 4-6 weeks:

  • Most people improve steadily and gradually for several weeks, then hit a plateau. When this plateau is still unacceptably painful, the following treatments may be considered. It is important to determine whether the pain is more in the leg or more in the back.
  • Patients with leg pain predominating (sciatica) may have the diagnosis confirmed by an MRI of the lumbar spine or a myelogram/CT scan. Two non-surgical treatments that can be helpful:
  • Epidural steroid injection (ESI): The MRI may suggest that an injection of corticosteroid (sometimes known as "cortisone") directly around the spinal nerves, may be helpful. This is a special procedure. ESIs are very safe, but the decision to have one should only be made after a discussion with the physician.
  • A selective nerve root block (SNRB) is an injection which treats only one nerve. Frequently, epidurals and selective nerve root blocks are done with X-ray control to make sure the medicine is placed exactly where it is needed.

Herniated Disc Patients With Back Pain Predominating:
There are three main treatments for patients who have back pain rather than sciatica:

  • Exercise:The mainstay of treatment for back pain is a good self directed home exercise program to increase abdominal strength, back muscle strength, and flexibility. There are many theories on which exercises are best. A physical therapist trained in back care will develop a personalized program with the patient over a one to three week period. Good abdominal strength is the key to a healthy back, therefore it is important for the patient to continue these exercises indefinitely.
  • Anti-inflammatory medicines (NSAIDs):These are often called arthritis medicines. It is important for the patient to give them a full three to four week trial since it takes this length of time for them to become fully effective. There are many types, and each individual can probably find one or two that work well.
  • Bracing: If symptoms persist over a long period of time, and exercise and NSAIDs have not improved the condition, a brace may be worn to provide additional support to the painful disc. When used with a good abdominal strengthening program, a brace may allow some people to be more active with less pain. Patients should choose a brace that is comfortable enough to wear for several hours at a time for the more strenuous activities.

Operative Treatment for Patients with Leg Pain Predominating

The 20% who do not respond to treatment after at least four to six weeks of non-surgical treatment and a few who have special problems may benefit from surgery, such as a microdiscectomy: a microscopic removal of the disc rupture to decompress the pinched nerve. Click to Enlarge

The indications for surgery include:

  • Intense leg pain.
  • The MRI shows a ruptured disc compressing a nerve which is consistent with the distribution of the leg pain.
  • Testing the nerve by stretching it ("nerve root tension signal") reproduces the leg pain.
  • There are no factors that would make surgery a risk for the patient.
  • Progressive worsening of nerve function, such as any loss of bowel or bladder function.

The Surgical Procedure: Microdiscectomy
The operation usually lasts one to two hours and provides good or excellent results in 95% of cases. Leg pain does not disappear immediately after surgery, but gradually disappears over several weeks.

  • A general anesthetic is used, and once asleep,the patient is placed in the prone or kneeling position on a specially padded frame.
  • A small incision is made directly over the disc, and a microscope is then used to find the compressed nerve and move it aside so that the ruptured portion of the disc can be seen and removed. Only the ruptured portion and loose pieces within about ½ inch of the hole are removed.
  • The space around the nerve is then thoroughly examined to make sure no small pieces of disc material might still compress the nerve.
  • Finally, antibiotic solutions are washed through the disc and incision to reduce the chances of infection. An absorbable suture is used to close the incision so that there are no stitches to be removed later.

What types of complications may occur?
All surgeries have risks, but complications with this procedure are few. Nevertheless, it is important for the patient to have a thorough discussion of these and other potential risks with the doctor before making a decision to have surgery.

  • Scar tissue formation (a 5% chance):When this surgery fails, it is due to an overgrowth of scar tissue around the nerve. Most people form some scar tissue in the area of a surgery, but for unknown reasons, some individuals form an extraordinary amount of scar which surrounds and irritates the nerve. It can form along the spinal nerve inside the spinal canal, or where the nerve exits the spine.
  • Infection (a 3-5% chance): Wound infection can happen any time an incision is made. The bacteria can come from the skin around the incision, the air in the operating room, or the bacteria that circulate in the bloodstream. The steps taken in the operating room to avoid infection are many. A dose of intravenous antibiotics right before surgery reduces the risk of infection even more. Persistent drainage from the wound 4-7 days after surgery usually means an infection is present. The patient might also have fever or chills, but this is not a reliable indication of an infection. Antibiotics are usually successful, but sometimes it is necessary to return to the operating room to wash out the incision. An infection does not usually cause the operation to fail, but may slow the healing process.
  • Spinal fuid leak (approximately 1%): Spinal fluid bathes the spinal cord and is contained inside a sac called the dura mater. Sometimes scar tissue forms between this sac and the ruptured disc. A hole can develop in the dura when the surgeon is looking for or removing the ruptured disc, allowing spinal fluid to leak out. When a spinal fluid leak is encountered, the hole is immediately repaired. Sometimes artificial blood clot is added to form a seal around the repair. Usually the patient is kept flat for 24 hours to allow the hole to heal before resuming a normal recovery.
  • Nerve damage at surgery (<1% chance): A nerve that has been compressed by a ruptured disc can be very fragile. Just moving the nerve to get at the disc behind it might cause this fragile nerve to be damaged. Fortunately, this is very rare, as is other surgical damage to the nerve.
  • Bleeding (rare): Blood loss is a rare complication . People whose blood does not clot blood normally are at increased risk. The large blood vessels in front of the spine may be damaged while removing disc material from within the disc. This is extremely rare (perhaps one in ten thousand cases) and requires emergency abdominal surgery to repair the bleeding vessel.
  • Recurrence (7%): Though technically not a complication of surgery, there is about a seven percent chance that the same disc will rupture again, most likely in the first six weeks after surgery when the hole in the disc annulus is healing. Even after six weeks the disc continues to be prone to injury. This is why the maximum weight a patient should lift is 8-10 pounds for six weeks after surgery. Abdominal strengthening exercises are recommended for life, since strong stomach muscles are good insurance against recurring disc problems.
  • Patients are usually seen by the surgeon at two, six and ten weeks after surgery.
  • A daily walking program should begin as soon as possible after surgery. At first it may be limited to a short distance, but it should be the main form of therapy for the first 6 weeks.
  • During this time, anything weighing more than a gallon of milk should not be lifted. By the end of the second week, strength and endurance should be improving.

A formal physical therapy program may begin at 4-6 weeks, and should lead to a lifetime home exercise program to minimize the chances of recurrence.

Operative Treatment for patients with Back Pain Predominating

Surgery is the final option, and should be used only if all other treatments have failed over several months. The back pain is often due to degeneration of the disc itself rather than a compressed nerve. When back pain is the main symptom, the surgery most often recommended is a fusion. In this operation, the vertebrae are fused together to limit motion.

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