Bones are strong and somewhat flexible. A fracture is a break or crack that occurs when the bone bends beyond its flexibility and cannot withstand some outside force. When there is a strong force, such as from a car accident, the bone may not be able to flex enough, and it will break. In bones that have lost their structural strength, even a minor movement can cause the bone to break.
A broken bone can hurt. The fibers in the nerves that surround bones get irritated by the swelling associated with the break and cause pain. The muscles near the fractured bone may also go into spasm trying to hold the bone together. This also causes pain.
Trabecular Bone and the Spine
As we grow older, through the remodeling process, there is a net loss of bone as the structure in the trabecular bone becomes thinner. Since 66% of the spine is made up of trabecular bone, the weakened bone becomes susceptible to spinal compression fractures. These fractures usually occur in the vertebrae of the lumbar (lower back) or thoracic (upper back) spine. A compression fracture in the spine occurs because the force of gravity is simply too strong for the weakened bones to withstand. Compression fractures of the spine are in part due to lifting heavy loads or poor body mechanics. But in bones that are weakened because of bone loss, even a small motion can cause them to break.
Compression fractures of the spine may — or may not — have related nerve damage resulting in pain. Physicians will sometimes do a CT scan or MRI to diagnosis a spinal fracture. They will be able to determine if a vertebrae has fractured because of the swelling around the bone. Treatment can include pain medication and/or a back brace along with bone building drugs plus calcium, vitamin D and a very specific exercise program. When spinal fractures cause pain, an analgesic called calcitonin is sometimes used with success. In some cases, vertebroplasty or kyphoplasty may be performed. In these procedures special cement is injected into the center of the collapse vertebra to strengthen and stabilize it. In the case of kyphoplasty the cement is encased in a protective balloon.
Trabecular Bone and Hip Fractures
The weakening of both cortical and trabecular bone can lead to hip fractures. The bones of the top of the thighbone when combined are about 40% trabecular and 60% cortical bone. Loss of mass in both types of bone in this region reduces bone strength and can result in a fracture at this site with a fall to the side on the hip.