There are probably almost as many ways of categorizing bone fractures as there are bones in the body (206!) — pretibial fractures, hip fractures, wrist or colles fractures, and spinal or vertebral fractures, just to name a few — but only a few bones are prone to osteoporotic fractures. Not surprisingly, all the various risk factors discussed above are associated with one or more specific type of fracture: instability is associated with falls to the side and greater occurrence of hip fractures; a tendency to walk more briskly is associated with people who fall forward and break their colles; and compression fractures of the spine — indeed all fractures — become more common in those whose capacity to continually mineralize trabecular bone becomes increasingly compromised with age.
In terms of mechanics, however, the two major types of fractures are stress fractures and compression fractures. Here’s an overview, with a little more emphasis on compression fractures, since they are far more common in older individuals with osteopenia and osteoporosis.
A stress fracture is really a crack within the bone. It is a partial fracture, or microfracture, rather than a complete fracture. Stress fractures most often result from overuse or repetitive stress on the bone. They often result from any increased amount or intensity of activity that occurs too rapidly to give the bone a chance to adjust.
Every day bone cells work to strengthen the bone, or allow the bone to become less strong, depending upon the forces at play in and on the body. The body is programmed to make new bone daily to replace the bone that has been broken down by the stresses of everyday activity. Ideally, the body produces as much new bone as it breaks down. In many cases, however, bone breakdown comes to exceed new bone formation. This can weaken the bone and lead to the microfractures known as stress fractures.
In many cases, stress fractures occur because an individual has increased her or his activity too quickly and the stress put upon the bone is too fast for the body to adapt. If the bone is not accustomed to the new loading, and if it is unable to strengthen itself quickly enough, stress fractures can develop. About half of all stress fractures occur in association with athletic activity. More than 50% of all stress fractures occur in the lower leg, the most common of these being tibial stress.
In contrast to stress fractures, a compression fracture is a complete bone break that disrupts the bone tissue and collapses the affected bone. The spinal vertebral body is the most common site of compression fractures. As the most common fractures associated with osteoporosis, vertebral compression fractures typically occur in the elderly osteoporotic spine; however, they can also occur as a result of severe trauma in the non-osteoporotic individual.
Some compression fractures are painful, while others go unnoticed. In the healthy body, these fractures will usually heal on their own within 8-12 weeks. The estimated rate of spinal fractures in Caucasian women has always seemed to me to be a bit high, but we don’t know the exact rate, since two-thirds of them go unnoticed. Recent data from the US Study of Osteoporotic Fractures suggest that some 18% of all US Caucasian women develop spinal fractures visible on x-ray between the ages of 68 to 84. For persons of African and Asian ancestry, the rates are lower.
Compression fractures of the spine result as a bone in the spine collapses. The fracture causes the vertebral body to lose height and form a wedge shape; this type of fracture is sometimes referred to as a wedge fracture.
But the occurrence of one spinal fracture does tend to be associated with further fractures. Carefully designed and conducted studies have shown us that the likelihood of incurring additional vertebral fractures is increased once you have already experienced one, even if you do not have low bone density. In fact, research suggests that around 20% of older women who experience a spinal fracture will experience another such fracture within a year. This has important health consequences because over time, accumulated compression fractures can lead to a noticeable loss of height and, if extreme, multiple spinal-vertebral fractures can cause significant pain, the development of a dowager’s hump, and problems with breathing, balance, and mobility. Which is why, as with so many health concerns, early identification and intervention are key!
Even the standard chest x-ray — ordered for a number of clinical indications — can be a useful tool for identifying vertebral fractures that might be due to osteoporosis. It’s unfortunate that spinal fractures are so often overlooked — or ignored — by radiologists. Studies done in the last decade reveal this to be the case in chest x-rays reviewed for moderate or severe fractures. When x-rays were reviewed, only around half of the spinal fractures that were clearly visible in retrospect had been mentioned on the radiologists’ formal reports! More disappointing are data showing that even when radiologists do report fractures noted on x-ray, fewer than half those patients receive appropriate treatment.
If this is our standard of care today, we have a long way to go. It goes without saying that if osteoporosis is undiagnosed, it is highly unlikely to be treated. Which is why, if you want to build healthy bones and live a long and fulfilled life, you also want to take good care of yourself. If you are over 50 and undergo chest x-ray for any reason, for example, we encourage you to speak up and request your providers to check for spinal fractures. Even more, if you are concerned about the possibility of vertebral fractures or deformities you can ask your doctor to do a vertebral morphometry scan at the same time they do the DEXA bone density test. This scan, done on the same bone density machine, will scan the spinal bones for small deformities as well as full fractures.
Overall, at the Center for Better Bones, we advise anyone who has experienced a low-trauma fracture of any kind to be especially diligent about self-care, for any osteoporotic fracture indicates vulnerability to further fractures. (For more in-depth information, refer to my article on spinal vertebral fractures and my article on fracture risk assessment, How can we tell who will fracture?)