A fracture is a broken bone. It will heal whether or not a physician resets it in its anatomical position. If the bone is not reset correctly, the healing process will keep the bone in its deformed position.

When a broken bone is manipulated and set into its natural position without surgery, the procedure is called a closed reduction. Open reduction requires surgery to expose the fracture and reset the bone.

Types of Fractures

Type of fracture

Description

Transverse

Occurs straight across the long axis of the bone

Oblique

Occurs at an angle that is not 90 degrees

Spiral

Bone segments are pulled apart as a result of a twisting motion

Comminuted

Several breaks result in many small pieces between two large segments

Impacted

One fragment is driven into the other, usually as a result of compression

Greenstick

A partial fracture in which only one side of the bone is broken

Open (or compound)

A fracture in which at least one end of the broken bone tears through the skin; carries a high risk of infection

Closed (or simple)

A fracture in which the skin remains intact

When a bone breaks so does the blood vessels in it. The blood flows out of the torn vessels and begins to clot over the first 6 - 8 hours. The clotting blood forms a fracture hematoma. The disrupted blood flow causes the bone cells around the fracture to die.

Student Activity:

Go to this link and follow along, learning to identify the different types of fractures.

Bones and Exercise

During long space missions, astronauts can lose approximately 1 to 2 percent of their bone mass per month. This loss of bone mass is thought to be caused by the lack of mechanical stress on astronauts’ bones due to the low gravitational forces in space. Lack of mechanical stress causes bones to lose mineral salts and collagen fibers, and thus strength. Similarly, mechanical stress stimulates the deposition of mineral salts and collagen fibers. The internal and external structure of a bone will change as stress increases or decreases so that the bone is an ideal size and weight for the amount of activity it endures. That is why people who exercise regularly have thicker bones than people who are more sedentary. It is also why a broken bone in a cast atrophies while its contralateral mate maintains its concentration of mineral salts and collagen fibers. The bones undergo remodeling as a result of forces (or lack of forces) placed on them.

Numerous, controlled studies have demonstrated that people who exercise regularly have greater bone density than those who are more sedentary. Any type of exercise will stimulate the deposition of more bone tissue, but resistance training has a greater effect than cardiovascular activities. Resistance training is especially important to slow down the eventual bone loss due to aging and for preventing osteoporosis.

Bones and Vitamin D

We all know that Calcium is needed to grow bones. Without calcium bone growth and strength suffers. Babies and children usually get their calcium from milk, but it can be a challenge for some adults to get enough calcium. Milk and cheese is a rich source of it but not always good for us. Smaller amounts of calcium can be found in leafy greens. 

Even when you get your calcium, the intestines are not able to absorb calcium without vitamin D. When the skin absorbs sunlight, the skin manufactures vitamin D. People that do not spend much time outdoors or people with dark skin can have a vitamin D deficiency. A vitamin D deficiency can in turn lead to bone problems because of a lack of calcium uptake.

Nutrients and Bone Health

Nutrient

Role in bone health

Calcium

Needed to make calcium phosphate and calcium carbonate, which form the hydroxyapatite crystals that give bone its hardness

Vitamin D

Needed for calcium absorption

Vitamin K

Supports bone mineralization; may have synergistic effect with vitamin D

Magnesium

Structural component of bone

Fluoride

Structural component of bone

Omega-3 fatty acids

Reduces inflammation that may interfere with osteoblast function

Students Read:

Skeletal System

Osteoporosis is a disease characterized by a decrease in bone mass that occurs when the rate of bone resorption exceeds the rate of bone formation, a common occurrence as the body ages. Notice how this is different from Paget’s disease. In Paget’s disease, new bone is formed in an attempt to keep up with the resorption by the overactive osteoclasts, but that new bone is produced haphazardly. In fact, when a physician is evaluating a patient with thinning bone, they will test for osteoporosis and Paget’s disease (as well as other diseases). Osteoporosis does not have the elevated blood levels of alkaline phosphatase found in Paget’s disease.

While osteoporosis can involve any bone, it most commonly affects the proximal ends of the femur, vertebrae, and wrist. As a result of the loss of bone density, the osseous tissue may not provide adequate support for everyday functions, and something as simple as a sneeze can cause a vertebral fracture. When an elderly person falls and breaks a hip (really, the femur), it is very likely the femur that broke first, which resulted in the fall. Histologically, osteoporosis is characterized by a reduction in the thickness of compact bone and the number and size of trabeculae in cancellous bone.

The above image shows that females lose bone mass more quickly than males starting at about 50 years of age. This occurs because 50 is the approximate age at which females go through menopause. Not only do their menstrual periods lessen and eventually cease, but their ovaries reduce in size and then cease the production of estrogen, a hormone that promotes osteoblastic activity and production of bone matrix. Thus, osteoporosis is more common in females, but males can develop it, too. Anyone with a family history of osteoporosis has a greater risk of developing the disease, so the best treatment is prevention, which should start with a childhood diet that includes adequate intake of calcium and vitamin D and a lifestyle that includes weight-bearing exercise. These actions, as discussed above, are important in building bone mass. Promoting proper nutrition and weight-bearing exercise early in life can maximize bone mass before the age of 30, thus reducing the risk of osteoporosis.

For many elderly people, a hip fracture can be life threatening. The fracture itself may not be serious, but the immobility that comes during the healing process can lead to the formation of blood clots that can lodge in the capillaries of the lungs, resulting in respiratory failure; pneumonia due to the lack of poor air exchange that accompanies immobility; pressure sores (bed sores) that allow pathogens to enter the body and cause infections; and urinary tract infections from catheterization.

Current treatments for managing osteoporosis include bisphosphonates (the same medications often used in Paget’s disease), calcitonin, and estrogen (for females only). Minimizing the risk of falls, for example, by removing tripping hazards, is also an important step in managing the potential outcomes from the disease.

Hormones are responsible for Bone Growth

Hormones That Affect the Skeletal System

Hormone

Role

Growth hormone

Increases length of long bones, enhances mineralization, and improves bone density

Thyroxine

Stimulates bone growth and promotes synthesis of bone matrix

Sex hormones

Promote osteoblastic activity and production of bone matrix; responsible for adolescent growth spurt; promote conversion of epiphyseal plate to epiphyseal line

Calcitriol

Stimulates absorption of calcium and phosphate from digestive tract

Parathyroid hormone

Stimulates osteoclast proliferation and resorption of bone by osteoclasts; promotes reabsorption of calcium by kidney tubules; indirectly increases calcium absorption by small intestine

Calcitonin

Inhibits osteoclast activity and stimulates calcium uptake by bones