Osteoporosis is a bone disease that causes your bones to weaken. To better understand osteoporosis and how it affects your spine, it helps to know spinal anatomy and what bones are made of.

Bone Tissue Types
There are two types of bone tissue in the body. Cortical bone is the hard outer shell of a bone. Trabecular bone is the honeycomb-like bone in the center of long bones and in the middle of the vertebrae. Bone is not dead tissue. Both types of bone are alive and in a continuous state of being broken down and regenerated by the body. This cycle of bone build up and break down keeps bones strong. But in osteoporosis, the balance between bone build up and break down is lost. Your body slowly starts to break down bone faster than it can regenerate it.

Trabecular bone is more active and is broken down and regenerated more quickly than cortical bone. Because of this, trabecular bone is more likely to be affected when the break down and regeneration of bone are out of balance in osteoporosis.

Bone Growth and Peak Bone Mass
Bone size grows throughout childhood and adolescence. During that time, your body produces more bone than it loses. At some point, you will be at your peak bone mass density, or BMD; that's as much bone as you'll ever have. For most people, this comes when you're between the ages of 18 and 25.

After you reach your peak bone mass, BMD either stays constant (with a balanced break down and regeneration of bone), or it starts to slowly decline if these two actions are out of balance. The greater the bone mass a person builds up as they're growing up, the less likely they are to suffer from osteoporosis. This is why proper nutritional intake of calcium, phosphorus, magnesium, and other minerals, as well as vitamin D, are so important during childhood and adolescence. Good nutrition and exercise are what build and help to maintain strong bones.

Basic Spinal Anatomy

The spine consists of individual bones called vertebrae. There are 24 vertebrae in the spine, plus the sacrum and tailbone (coccyx). Most adults have seven vertebrae in the neck (the cervical vertebrae), twelve vertebrae from the shoulders to the waist (the thoracic vertebrae), and five vertebrae at the lower back (the lumbar vertebrae). The sacrum is made up of five vertebrae between the hipbones that are fused into one bone. The coccyx is made up of small fused bones at the tail end of the spine.

Because the vertebrae of the spine are primarily trabecular bone, they are more likely to be weakened by osteoporosis. Standing erect puts a great deal of pressure on the vertebrae, which means that weakened ones can fracture and start to compress or collapse. If one vertebra is fractured, it puts stress on other vertebrae and puts them at greater risk of fracture.