Test your knowledge about osteoporosis (porous bone) before reading the article. Answer the following "true or false" questions.

1. Osteoporosis is a disease for older population and has nothing to do with spinal cord injury (SCI).
   TRUE     FALSE
2. There is no relationship between the level of SCI (paraplegics or tetraplegic) and osteoporosis.
   TRUE     FALSE
3. There are many symptoms associated with osteoporosis.
   TRUE     FALSE
4. There is no difference in the frequency of osteoporosis between SCI and general population.
   TRUE     FALSE
5. You can treat the osteoporosis but you can not prevent it.
   TRUE     FALSE

If your answers to the above questions are "False", you know good deal about osteoporosis.

What is Osteoporosis?

By definition osteoporosis, simply means porous bone. It is a disease that is manifested by low bone mass and major structural damage to the bone tissue, leading to bone fragility and an increased vulnerability to fractures especially at the hip bones, spine, and wrist. Calcium and phosphorus are the two main minerals that are part of the make up of a strong bone. In osteoporosis, these two minerals have significantly reduced in the bones leading to fragility and weakness.

Osteoporosis is one of the inevitable complications following spinal cord injury (SCI). It usually has no clinical signs or symptoms that may persuade the patients to seek medical treatment. It is sometimes called a silent disease. Usually, X-rays following a broken bone reveal not only the fracture but also significant bone loss and osteoporosis is detected in the SCI population. The major affected areas of the body by osteoporosis following SCI are hip bones and lower leg bones. Unfortunately, osteoporosis is considered a secondary complication following SCI and the majority of medical attention is paid to treat the primary patient’s complications. In these cases treatment and or prevention of osteoporosis is ignored.

Does bone loss happens in all SCI in the same magnitude, irrespective of type or time of injury?

Bone loss following SCI occurs throughout the body with the exception of the skull. The level of bone loss depends on the level of injury, completeness of injury, and time following the injury. The higher the level of injury the higher the level of bone lose, for example SCI with tetraplegia loose more bone at the wrist and arm in addition to the legs, while person with paraplegia usually does not loose significant bone on their arms and wrist. In fact, the bone mineral density of the arms of paraplegic patients returns to near normal by the 10-year post injury. Usually, the leg bones are the bones most affected, followed by the hip bones and the arms. During the first four months following injury the loss is most rapid, within the first year usually between 25-43% of bone is lost in the upper part of the leg bones (femur) . Studies have shown that bone loss is usually continues for the next ten years. Interestingly, the spine shows some increase in bone density after ten years. Some investigators relate that to weight bearing activities due to sitting on a wheelchair for a long time.

There is a direct relationship between muscle activity and bone mass. The more active muscles a SCI person has the less bone he/she will lose. In fact, individuals with complete injuries (no muscle function) tend to have less bone mineral density than those with incomplete lesions (some muscle function). In fact, those SCI who have incomplete injury show higher levels of bone density in areas that muscles are more active and strong.

Can spasticity prevent bone loss?

Opinions regarding the effect of spasticity on bone mass is controversial. Some studies have found that bone loss is less in patients exhibiting spasticity, compared with those with no spasticity, however some studies have shown no effect.

Why osteoporosis is more frequent in SCI than general population?

In people without SCI, the bones are kept strong through regular muscle activity or by bearing weight. Following spinal cord injury, muscle activity and walking is no longer possible. When muscle activity is decreased or eliminated and the legs no longer bear the body's weight, they begin to lose calcium and phosphorus and become weak and brittle. The bone loss may be aggravated by the loss of muscle traction on bone or other neural factors associated with SCI.

What are the symptoms associated with osteoporosis?

Osteoporosis by itself has no symptom. However, the main risk of osteoporosis is fracture. Once the bones become brittle, they fracture easily. At the same time, a brittle bone takes much longer to heal. The frequency of fracture after SCI has been reported to be 14% at 5 years, 28% at 10 years, and 39% at 15 years post-injury. These incidence rates are based on both inpatients and outpatient studies and have been confirmed. Usually fractures happen in the areas with the highest level of bone loss and the most areas reported have been shine bone (tibia) and around the knee area. Fracture rates in the lower legs are 10 times greater in patients with complete SCI compared to patients with incomplete injuries. Paraplegic patients are at higher risk than tetraplegics, due to the higher level of function, mobility, and participation in physical activities. Fractures usually happens following everyday life activities and not a major trauma.

What types of tests are available for Osteoporosis?

There are certain blood and urine tests that can be perfumed to diagnose the osteoporosis, especially measuring the calcium and phosphorus in the blood and urine. Usually, the SCI individual lose calcium and phosphorus from the bone to the blood stream and from the blood into the urine. A significant increase in blood and urine calcium could be a sign of osteoporosis. There are also other more advanced tests that your doctor can order to identify the osteoporosis. Quantitative computed tomography (QCT) scans can evaluate the bone and it’s content. Dual energy x-ray absorptiometry (DEXA) scan, can record absolute bone mineral densities in various regions of the body. They are most commonly used for clinical studies.

How do you treat osteoporosis?

Unfortunately, at the present time, there is no way to reverse osteoporosis once it has occurred. There is also no standards for follow-up care following the diagnosis of osteoporosis in the SCI population. Thus, early prevention is the focus in treating osteoporosis following SCI. Appropriate nutritional intake of calcium and vitamin D and proper precautions in transfers and wheelchair sports can help in prevention of osteoporosis and, later, in the prevention of fractures. During the chronic stage of SCI, increasing the weight bearing activities and using the legs to support body will increase the load on the bone and may reduce or slow down the osteoporotic process. Standing using a standing frame or a standing table, as well as braces for functional or parallel bar walking may help prevent weakening of the bones. Newer techniques, such as electrical stimulation of the leg muscles, may decrease osteoporosis as well, however, more research needs to prove these effects.

Fracture:

The primary treatment is to prevent fractures. Prevention of falls or striking the legs against objects are some precautionary measures to prevent fractures. Following the range-of-motion guidelines from therapists to avoid putting excessive stress or pressure on bones is advisable. Walking with braces may help to limit the amount of osteoporosis that develops in the legs.

Medications:

Bisphosphonates - These are the most well studied class of medications and have been found to have a positive effect in preventing osteoporosis following SCI. Their mechanism of action is though prevention of the activities of the cells that absorb calcium from the bone. It should be noted that, studies on the effects of bisphosphonates in the SCI population, are preliminary, and there is no consensus on drug of choice or a dosing regimen. There are some other medications that have been used for other forms of osteoporosis, however their effects have not been studied on SCI population.

Patient Education:

Spinal cord injured should be educated as soon as possible following their injury on their nutritional needs, techniques for transportation, wheel chair operation, sports safety, and the benefits of early mobilization. These early educations may help reduce the amount of osteoporosis and prevent the fractures that may result.

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