Bone is the hardest tissue in the human body, but when bones are subjected to forces that exceed their strength, they may break in several different ways.
Illustration by Frank Forney. © 2016 Cengage Learning®.
The bones in the human body are very strong, but they can be broken (fractured) as a result of trauma. Breaks can range in severity from hairline fractures that require minimal treatment to shattered bones that require surgery and may result in permanent damage.
Ken knew the steps to the attic were steep, but when his little sister ran off with his toy airplane, he took the stairs two at a time. Halfway down he slipped. Ken landed in a heap at the bottom and immediately howled in pain. When he got up, his arm was twisted in a strange way, and his elbow would not bend.
Ken's mother rushed him to the emergency room where doctors took x-rays of his arm. He had broken the bone in the upper part of his arm as well as his elbow. The breaks were so bad that Ken had to have surgery that afternoon. The doctor put a metal pin in his elbow to hold the bones together while they healed. After surgery, Ken's arm had to be in traction for two weeks. Being in traction means that he had to lie on his back in bed while his elbow was held in place by a special device hanging from the ceiling. This device put tension on his arm and elbow in just the right places to allow them to heal properly. After getting out of the hospital, Ken had a plaster cast on his whole arm for another eight weeks. Ken's arm and elbow healed completely, but every so often his elbow aches when he plays baseball.
Bone is the hardest tissue in the human body, but when bones are subjected to forces that exceed their strength, they may break. The terms break and fracture mean the same thing.
Bones break when they are subjected to extreme force or stress. The likelihood that a bone will break depends on the location of the bone in the body, the thickness of the bone, and the circumstances under which the force is applied. The most commonly broken bones are those in the wrist, hip, and ankle.
Bone is living tissue and, like other living tissue in the body, bone is affected by genetics, hormones, diet, physical activity, disease, and drugs. All of these factors determine which bones are more or less prone to injury. In addition, the strength of bone and the forces acting on bone vary with age, so the types of fractures and the number of people affected by them vary with age as well.
Other factors that weaken bone and predispose individuals for bone fracture include those associated with low bone-mineral density, such as osteoporosis, age (over 50), menopause and postmenopause in women (due to low estrogen levels), previous fractures, ethnicity (Caucasian and Asian groups have a higher incidence of osteoporosis), long-term corticosteroid * therapy, rheumatoid arthritis * , elevated levels of parathyroid hormone (associated with hyperparathyroidism), and androgen deficiency * in men. In addition, some cancer treatments, immunosuppressants * , steroids, antipsychotics * , and anticonvulsants * may predispose individuals who use them to bone fracture. Some diseases associated with nutritional deficiencies and/or immobility, such as Crohn's disease, rheumatoid arthritis, blood disorders, and endocrine disorders, may predispose a person to poor bone health.
Healing time also varies with the severity of the break as well as the patient's general state of health and nutrition.
Many types of trauma (e.g., skiing or car accidents) can cause a bone to break. However, some people are more prone to breaks because they have genetic conditions or bone diseases that weaken their bones, such as:
Broken bones may be treated by realigning the bones in their proper position, if necessary (a process called reduction), and then holding them in place while they heal.
How a broken bone is treated depends on where in the body it is located and how severe the break is. In the case of a stress fracture, a device called a splint may be used to immobilize the injured area while it heals. An arm sling may also be used to keep a person from using an injured arm. When a person has a simple fracture, the doctor guides the bones back into their proper place, if necessary, and then immobilizes the injured area with a cast made of plaster or fiberglass.
Other more serious types of fractures can require surgery. For example, in Ken's case, realigning the bones was not a straightforward task. An orthopedic surgeon (bone specialist) needed to open the site of the fracture surgically and use metal pins and plates to hold the bones together while they healed. Ken's injury required his arm to be in traction for two weeks before having a cast for an additional two months.
The healing process for fractures takes place in three stages known as inflammation, repair, and remodeling. The first phase (inflammation phase) occurs as damaged soft tissue in the surrounding area becomes swollen and painful. This swelling and pain may last from a few days to a few weeks. The second phase (repair phase) may last from a few weeks to a few months as bone regeneration occurs and the new soft bone without calcium (callus) moves from being soft to being hard and strong. The third stage (remodeling phase) may last for many months as the bone builds itself back to its normal, hardened state. Splints, casts, and slings are used to keep bones in place while they heal.
Healing occurs when the bone tissues produce a substance called callus, which binds the broken pieces together. Healing time varies with age. A fracture that may take three weeks to heal in a four-year-old may take three months to heal in an adult. Casts for simple breaks usually stay on for six to eight weeks, but more severe breaks may require a cast for a much longer period.
Many people recover completely from breaks and fractures. One possible complication that may increase recovery time is osteomyelitis, an infection of the bone. Osteomyelitis may be acute or chronic, and it is usually caused by bacteria entering the bone. The infection may occur at the fracture site or in another part of the body; in the latter case, the infection then travels to the bone via the bloodstream. Osteomyelitis may naturally occur when a person sustains a compound fracture (often from physical trauma) in which a break in the skin occurs. The open skin allows bacteria to enter, and osteomyelitis may result. Antibiotics are often prescribed for compound fractures in order to prevent or eliminate infection, which minimizes the possibility of osteomyelitis. Compound fractures may take a long time to heal, necessitating prompt and aggressive antibiotic therapy.
See also Arthritis • Osteomyelitis • Osteoporosis • Rickets • Strains and Sprains • Trauma
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American Association of Orthopaedic Surgeons. 9400 W Higgins Rd., Rosemont, IL 60018. Telephone: 847-823-7186. Website: http://www.aaos.org (accessed November 23, 2015).
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* corticosteroid (KOR-ti-ko-STERoid) is one of several medications that are prescribed to reduce inflammation and sometimes to suppress the body's immune response.
* rheumatoid arthritis (ROOmah-toyd ar-THRY-tis) is a chronic disease characterized by painful swelling, stiffness, and deformity of the joints.
* androgen deficiency (AN-drogen de-fish-ens-see) is reduced male hormones in men, also called male menopause.
* immunosuppressants (im-yoo-nosu-PRES-ants) are substances that weaken the body's immune system.
* antipsychotics are a type of medication that counteracts or reduces the symptoms of a severe mental disorder such as schizophrenia.
* anticonvulsants (an-tie-kon-VUL-sents) are medications that affect the electrical activity in the brain and are given to prevent or stop seizures.
* bone marrow is the soft tissue inside bones where blood cells are made.