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American Academy of Orthopaedic Surgeons
March 2007

What bones are made of

"Thank goodness it’s only a fracture. I thought it might be broken." People often think that a fracture is less severe than a broken bone, but fractures are broken bones.
To understand why bones break, it helps to know what bones do and what they are made of. The bones of the body form the human frame, or skeleton, which supports and protects the softer parts of the body. Bones are living tissue. They grow rapidly during one’s early years, and renew themselves when they are broken.

Bones have a center called the marrow, which is softer than the outer part of the bone. Bone marrow has cells that develop into red blood cells that carry oxygen to all parts of the body and into white blood cells that help fight disease. Bones also contain the minerals calcium and phosphorus. These minerals are combined in a crystal-like or latticework structure. Because of their unique structure, bones can bear large amounts of weight.

How fractures occur

Bones are rigid, but they do bend, or "give" somewhat when an outside force is applied to them. When this force stops, bone returns to its original shape. For example, if you fall forward and land on your outstretched hand, there’s an impact on the bones and connective tissue of your wrist as you hit the ground. The bones of the hand, wrist and arm can usually absorb this shock by giving slightly and then returning to their original shape and position. If the force is too great, however, bones will break, just as a plastic ruler breaks after being bent too far.

Types of fractures

The severity of a fracture usually depends on the force that caused the fracture. If the bone’s breaking point has been exceeded only slightly, then the bone may crack rather than breaking all the way through. If the force is extreme, such as in an automobile collision or a gunshot, the bone may shatter. If the bone breaks in such a way that bone fragments stick out through the skin or a wound penetrates down to the broken bone, the fracture is called an "open" fracture. This type of fracture is particularly serious because once the skin is broken, infection in both the wound and the bone can occur.

Treating your fracture

Because fractures hurt and make it difficult if not impossible to use the part of the body that is injured, most people call a doctor or seek emergency care quickly. In some cases, however, a person can walk on a fractured bone in the leg or foot, or use a fractured arm. Just because you can use your hand or foot does not mean that you do not have a fracture. If you think a bone may be broken, you should seek medical help immediately. A medical examination and x-rays are usually necessary to tell for sure and to ensure proper treatment.

It is very important to control the movement of a broken bone. Moving a broken or dislocated bone can cause additional damage to the bone, nearby blood vessels, and nerves or other tissues surrounding the bone. That’s why people giving first aid or emergency treatment may splint or brace your injury before medical treatment is given. Also, if there is an open wound it should be covered by a clean cloth or bandage on the way to further medical treatment.

At the emergency room, clinic or doctor’s office, the physician usually applies a splint to prevent further damage, to lessen the pain and to help stop any bleeding. The patient is usually asked to recline and elevate the injured part. Elevation helps to reduce bleeding and swelling.

X-rays can help the physician determine whether there is a fracture, and if so, what type of fracture it is. If there is a fracture, the doctor will "reduce" it, by restoring the parts of the broken bone to their original positions. "Reduction" is the technical term for this process.
All forms of treatment of broken bones follow one basic rule: the broken pieces must be put back into position and prevented from moving out of place until they are healed. Broken bone ends heal by "knitting" back together with new bone being formed around the edge of the broken parts.

The specific method of treatment depends on:

  • The severity of the break.
  • Whether it is "open" or "closed."
  • The specific bone involved-a broken bone in the spine (vertebra) is treated differently from a broken leg bone or a broken rib.

Types of treatment

The following treatments are used for various types of fractures:

  • Cast immobilization -A plaster or fiberglass cast is the most common type of fracture treatment, because most broken bones can heal successfully once they have been repositioned and a cast has been applied to keep the broken ends in proper position while they heal.
  • Functional cast or brace -The cast or brace allows limited or "controlled" movement of nearby joints. This treatment is desirable for some but not all fractures.
  • Traction -Traction is usually used to align a bone or bones by a gentle, steady pulling action. The pulling force may be transmitted to the bone through skin tapes or a metal pin through a bone. Traction may be used as a preliminary treatment, before other forms of treatment.
  • Open reduction and internal fixation-In this type of treatment, an orthopaedist must perform surgery on the bone. During this operation, the bone fragments are first repositioned (reduced) into their normal alignment, and then held together with special screws or by attaching metal plates to the outer surface of the bone. The fragments may also be held together by inserting rods down through the marrow space in the center of the bone. These methods of treatment can reposition the fracture fragments very exactly. Because of the risks of surgery, however, and possible complications, such as infection, they are used only when the orthopaedic surgeon considers such treatment to be the most likely to restore the broken bone to normal function. 
  • External fixation-In this type of treatment, pins or screws are placed into the broken bone above and below the fracture site. Then the orthopaedic surgeon repositions the bone fragments. The pins or screws are connected to a metal bar or bars outside the skin. This device is a stabilizing frame that holds the bones in the proper position so they can heal. After an appropriate period of time, the external fixation device is removed.

Each of these treatment methods can lead to a completely healed, well-aligned bone that functions well. Remember that the method of treatment depends on the type and location of the fracture, the seriousness of the injury, the condition and needs of the patient, and the judgment of the orthopaedist and the patient.

Successful treatment of a fracture also depends greatly on the patient’s cooperation. A cast or fixation device may be inconvenient and cumbersome, but without one a broken bone can’t heal properly. The result may be a painful or poorly functioning bone or joint. Exercises during the healing process and after the bone heals are essential to help restore normal muscle strength, joint motion and flexibility. Help your broken bone heal properly-follow your orthopaedist’s advice.

Preventing broken bones

Even though healthy bones are very strong, any bone will break if the force applied against it is great enough. Bones that are weakened by disease or misuse may break more easily than healthy bones. To develop and maintain healthy bones, a person needs adequate amounts of calcium and proper exercise.

Because of the way bones are made, calcium is very important in the growth, development, and maintenance of strong bones. Adequate amounts of calcium are necessary as a child grows and for the adult as well. Women, in particular, must have enough calcium in their diet. The female hormone estrogen regulates the use of calcium in women’s bodies.

Following menopause, when women produce far less estrogen, calcium regulation is more difficult. So it is very important that women make their bones as strong as possible before menopause, through weight-beating exercise and adequate calcium in their diets. In some women after menopause, bones fracture very easily because they have been weakened by calcium depletion.

Because of the way bones are made, they also get stronger with regular but not excessive exercise. If a person is active, bones will become stronger and more dense. The bones of an inactive person are often not as strong and may fracture more easily than those of an active person. For this reason, older people should try to remain physically active.
Proper diet and exercise, along with an understanding of what bones are made of and how they break, may help in preventing some fractures. If you do break a bone, seek medical treatment and remember-follow your orthopaedist’s advice.

This brochure has been prepared by the American Academy of Orthopaedic Surgeons and is intended to contain current information on the subject from recognized authorities. However, it does not represent official policy of the Academy and its text should not be construed as excluding other acceptable viewpoints.

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