What Causes Back Pain

There are a number of causes of back pain. The spine is a complex structure, with a number of joints and nerves, each of which is capable of producing severe pain. For this reason, generalized back pain is not only common, but also very difficult to treat with directed therapy. When the pain begins to radiate down the leg, a doctor can tell that a certain nerve is affected; then it is possible to direct therapy to a specific target.

The lower back is termed the lumbar (lum-bar) spine. The lowest nerves of the lumbar spine not only make up the sciatic nerve, but also are the cause for the majority of back pain that occurs. The spine not only helps to support the weight of the body, but also allows for trunk mobility. This motion puts strain on the most flexible areas of the back, especially the lowest two disc spaces in the lumbar spine. The discs are the spongy cushions between the bones of the spine, supplying mobility to the spinal while protecting the bones from repeated stress. It is the constant strain that these discs take that leads to their propensity to rupture. The disc is made of a hard, fibrous shell, the anulus (an-you-lus), which surrounds a more spongy middle, the nucleus. Repeated stress and injury, combined with weight, posture, and genetics, as well as simple bad luck, can lead to the nucleus rupturing through the anulus. The medical condition that results is a herniated nucleus pulposus (her-knee-ate-ed new-klee-us pul-poe-sis, abbreviated HNP).

The disc spaces are named for the bones that they are sandwiched between. The lumbar spine is made up of five bones, or vertebrae (ver-ta-bray), which ends at the part of the pelvis called the sacrum (say-krum). The disc spaces that most commonly rupture are the lowest two - between the L4 and L5 vertebrae and between the L5 vertebrae and the sacrum. The L4-L5 and the L5-S1 disc spaces are the most commonly injured because, being lowest down in a very mobile area of the spine, the most force is put on them during the course of the day.

When a disc ruptures, a piece of the nucleus pushes through the anulus right where the nerve associated with that disc space lies. Because the nerve is tethered at the point in which it leaves the spine, the disc material compresses the nerve. Compressed nerves hurt. Taking weight off the spine by lying down can alleviate some of the pain. Conversely, sitting or straining, or even coughing or sneezing, puts more pressure on the nerve, thus causing more pain.

For that reason, many physicians recommend bed-rest or light activity during an acute phase of a disc rupture. Pain relievers and/or muscle relaxants are used for symptomatic relief. Clearly, some of the pain is related to inflammation around the nerve. Therefore, patients are often put on steroid packs or anti- inflammatory medications (NSAIDs such as ibuprofen).Steroids tend to help the pain a lot, but because of the side effects, they can only be used for a short period of time. Other nonsurgical treatments include physical therapy and direct injections of steroids near the nerve.

The vast majority of disc ruptures will heal themselves when given enough time. Therefore, much of the treatment is essentially designed to alleviate symptoms while the body heals itself. Given several weeks of these treatments, most patients will be significantly better. It is the exceptional patient who remains in severe pain. When a patient's pain worsens, fails to improve, or when a patient experiences muscle weakness, surgery may then be considered.

Several surgical options exist to treat lumbar disc herniations. Essentially, these options are just variations of the same theme. The classic approach, lumbar laminectomy (lamb-in-eck-toe-me), begins with stripping the muscle off of the back over the area of the disc rupture. A microscopic discectomy (dis-eck-toe-me) begins with the same step, but because a microscope is used, the incision is smaller. Over the last five years, a novel approach has been developed that does not require cutting the over- lying muscles off of the bone. This approach, Micro Endoscopic Discectomy (MED), has been gaining favor with surgeons and patients alike. When the muscle opening is gently enlarged as opposed to cut, much of the post-operative pain is avoided. With MED, a smaller amount of bone is removed and much of the normal anatomy of the back is left intact. When all is said and done, the latter steps of all these procedures are the same - removing a small window of bone, moving the nerve, and removing the ruptured disc.

 

Most low back pain is triggered by some combination of overuse, muscle strain, and injury to the muscles, ligaments, and discs that support the spine. Many experts believe that over time muscle strain can lead to an overall imbalance in the spinal structure. This leads to a constant tension on the muscles, ligaments, bones, and discs, making the back more prone to injury or reinjury.

The causes of pain in the low back, or lumbosacral region, tend to add on to one another. For example, after straining muscles, you are likely to walk or move in different ways to avoid pain or to use muscles that aren't sore. That can cause you to strain other muscles that don't usually move that way.

The most common causes of low back pain are:

• Injury or overuse of muscles, ligaments, facet joints, and the sacroiliac joints.

• Pressure on nerve roots in the spinal canal. Nerve root compression can be caused by:

o A herniated disc, often brought on by repeated vibration or motion (as during machine use or sport activity, or when lifting improperly), or by a sudden heavy strain or increased pressure to the lower back.

o Osteoarthritis (joint degeneration), which typically develops with age. When osteoarthritis affects the small facet joints in the spine, it can lead to back pain. Osteoarthritis in other joints, such as the hips, can cause you to limp or to change the way you walk. This can also lead to back pain.

o Spondylolysis and spondylolisthesis, vertebra defects that can allow a vertebra to slide over another when aggravated by certain activities.

o Spinal stenosis, or narrowing of the spinal canal, which typically develops with age.

o Fractures of the vertebrae caused by significant force, such as from an auto or bicycle accident, a direct blow to the spine, or compressing the spine by falling onto the buttocks or head.

o Spinal deformities, including curvature problems such as severe scoliosis or kyphosis.

• Compression fractures

Compression fractures are more common among postmenopausal women with osteoporosis, or in men or women after long-term corticosteroid use. In a person with osteoporosis, even a small amount of force put on the spine, as from a sneeze, may cause a compression fracture.