A fracture is any breakage of a bone, and a compression fracture is a particular type of break, pretty much unique to the vertebrae of the spine. To understand compression fractures, and the possible complications, we need to visualize how our vertebrae are put together.
Humans usually have 24 vertebrae in their spines. A few people may have one more or less borrowed from or fused to their sacrum. All the vertebrae, except the topmost ones, have a large round body, rather like an inch-long one-inch high cut off dowel.
Attached to the back of the vertebrae are two pedicles, connected in the back by two laminae. This creates a hole in the center which the spinal cord runs through. Vertebrae also have little joints, called facets or articular processes, where each vertebra connects to the one above and below it. Since these are joints, they give the spine its ability to move. Vertebrae in the chest also have facets where the ribs attach.
Between the vertebrae are discs, (fibrous rings) filled with a gelatinous material which cushions the vertebrae. A slipped or ruptured disc happens when the fibrous band ruptures and some of the gelatinous material spills out and presses on a nerve coming from the spinal cord, or presses directly on the spinal cord.
The spinal cord within the spinal canal is surrounded by fluid and wrapped in heavy membranes. Together with the bony layer produced by the laminae they protect this vital structure from trauma. An exposed cord would be subject to damage just from being poked, but the vertebrae protect the cord from everything but major trauma.
A compression fracture of a vertebra occurs when the round dowel-like body collapses vertically. A common cause is a fall in which the person lands on their feet. The shock is transmitted through the legs and pelvis, (which are usually strong enough not to fracture), up into the spine. If the force is strong enough, one or several vertebral bodies may collapse, producing a compression fracture.
If both the front and the back of the vertebral body collapse, it is referred to as a burst fracture, and the risk of spinal cord injury is great. Such compression fractures may require surgery to remove any bone fragments pressing on the spinal cord, and to stabilize the vertebral body. If scans and neurological examination don’t show any pressure on the cord, surgery may be avoided and the vertebral body allowed to heal on its own.
Although severe trauma accounts for most fractures in men, they are even more common in women with osteoporosis in which calcium loss from the vertebrae and other bones greatly weakens them, making the bones much more susceptible to fracture. Hip fractures are common because of this, but vertebral fractures occur so often that we used to consider them a normal accompaniment of aging.
We now realize that these compression fractures are a result of a osteoporosis which can be treated. In osteoporosis, the compression tends to be greater in the front of the vertebral body than in the back where the spinal cord is located. Because of this, cord damage is not common, and indeed a woman may not even have much pain, beyond the usual aches that she gradually becomes accustomed to.
It is this vertebral collapse that leads to the loss of height that many women notice in their 60s and 70s, and because it is the front of the vertebral body that usually collapses, the woman’s upper body bends forward, producing the so called dowager’s hump that many older women have.
With the development of bone density tests, osteoporosis may now be diagnosed early and treated. Women at risk tend to be white and of northern European extraction, but any woman can develop it. Early menopause, or loss of menstrual periods when young due to sports, as well as smoking, drinking alcohol, a sedentary life style, a low calcium intake and removal of the ovaries without hormone replacement are all risk factors.
Some diseases of the endocrine glands, specifically hyperthyroidism and hyperparathyroidism will accelerate calcium loss from the bones. Taking excessive amounts of thyroid hormone may also be risky.
A number of treatments for osteoporosis are now available, so women with several risk factors, or women whose mothers lost height as they grew older, should get bone density tests when they are in their late 40s and early 50s.
Women who don’t want to take hormone replacements can be treated with raloxifene, an antiestrogen that protects the bones, and reduces the risk of breast cancer at the same time. All women should take calcium supplements with vitamin D starting in their 40s. Specific drugs to improve bone strength such as alendronate (Fosamax) are also available.
Men can also get osteoporosis, but usually later than women, in their 70s or 80s. Fortunately most men at that age they don’t engage in occupations that will cause them to fall landing on their feet, or we would see many more serious compression fractures with spinal cord injury.