Back Pain, Specific Disorders

By Dr. Sawatzky

There are some definite risk factors for a herniated disc. Anyone over 182 cm (6 ft) tall or weighing more than 82 kg (180 pounds) on enrolment in the US army had a risk of herniated disc 20 years later 2.6 times higher than average.

Virtually all of us have a small protrusion in the center of at least one disk that is easily seen on MRI. This finding has no practical significance and causes no serious problems in the lumbar spine. There is a lot of room in the spinal canal at this level because the spinal cord is gone and the spinal nerves running down the canal take up relatively little space. Unfortunately, if the herniated disk protrudes to one side, it can pinch the spinal nerve as it is exiting the spine between the vertebrae. If this happens you will experience severe pain in the area supplied by the nerve. In the lumbar spine these nerves supply the legs. Therefore, even though the nerve is compressed in the back, the pain will be felt in the legs. It is often very difficult to tell if back and/or leg pain is from a pinched spinal nerve, or something else. As a rough rule of thumb, if the pain does not extend below the knee, it is unlikely to be from spinal nerve compression. If you stretch the spinal nerve by lying on your back relaxing, and someone raises your straight leg up towards the ceiling, the pain will become MUCH worse if the spinal nerve is pinched. In most other types of leg pain this test is not too uncomfortable. Be warned that this test is very difficult to do reliably. Another sign of spinal nerve compression is weakness in the muscles of the leg. Of course, the pain will usually be in only one leg as it would be extremely difficult for one herniated disc to put pressure on the spinal nerves leaving the spine on opposite sides of the vertebra.

If you have spinal nerve compression, you will need to see your doctor. They will most likely try a brief period of bed rest (maximum 48 hours), pain killers, physiotherapy, etc. to try and get the problem to settle down without surgery. Most of the time the pain will resolve over 6 to 12 weeks. As an aside, bed rest should be for a maximum of two days and then graduated return to full activity. Sometimes, surgery to reduce pressure on the nerve will be required. Surgery is used as a last resort for two reasons. First, if you have had spinal surgery, you are 10 times more likely than the general population to require more spinal surgery. Second, a significant percentage of people will NOT get relief from spinal surgery and the chance of success after a second or third surgery is low. The difficult decision of whether to operate or not has to be made by a spinal surgeon with a lot of experience.

Obviously, you cannot dive if you have symptoms of spinal nerve compression. After the pain has resolved, or you have had surgery, whether you can safely return to diving or not depends mostly on your flexibility and fitness level. Spinal surgery most likely results in abnormal circulation to that part of the spine, and that could be expected to put the person at increased risk of DCS if they return to diving. However, at the moment there is no good data to suggest that this is a practical problem for recreational diving.

There are many other, rare, anatomical problems with the spine that can cause back pain. Bone spurs can cause compression of the spinal cord and spinal nerves. Bone spurs are common. Bone spurs that cause nerve compression are rare.

Spondylolisthesis is the forward slippage of one vertebra over the next. This is most commonly the fifth lumbar vertebra slipping forward over the sacrum, but sometimes the fourth lumber vertebra slides forward over the fifth. This problem can only occur when there is a fracture or defect of the posterior arch of the vertebra and is relatively uncommon. It becomes significant when the vertebrae become so displaced that the spinal nerves become trapped between the two misaligned vertebrae. Small amounts of displacement can be treated with exercise and therapy but by the time the nerves become involved, surgery of one form or another is the only option. Obviously, people with these kinds of problems cannot dive until the problem has been successfully treated.

Ankylosing spondylitis (AS) is an interesting inflammatory arthritis of the spine that also sometimes involves the hips and other joints. It occurs in approximately 2 of every 1,000 people so it is rare but not uncommon. There is a strong genetic component to this disease in that over 90% of people who develop AS are tissue type HLA B-27. However, only 2% of people who are HLA B-27 will develop AS. It appears that you need to be HLA B-27 positive, and have an infection with Klebsiella or Chlamydia to develop AS. It usually starts in young adults and slowly progresses over decades. I know one person with a relatively severe form of the disease whose spine was essentially fused solid by the time he was 30. Fortunately, he had maintained excellent posture and his spine had fused straight. He was very active in sports and had surprisingly few limitations. This chronic inflammatory disease could be expected to increase the risk of DCS, but should have few practical limitations for recreational diving.

There are many other specific back problems that can cause pain, including infections and cancers. If you have chronic or intense back pain, you should see your family doctor to rule out these potentially serious problems. However, in the vast majority of people there will be no obvious specific cause for their back pain. In the next column I will explain my personal approach to this very common and significant problem.