4.3.2 Fractures
A break in a bone is called a fracture.Fractures commonly happen because of car accidents，falls，or sports injuries.Other causes are low bone density and osteoporosis，which cause weakening of the bones.
The different types of fractures are classified by extent of damage（Fig.4-3）.
Fig.4-3 Types of Fracture
A closed（simple）fracture is one in which the bone is broken but no external wound exists.An open（compound）fracture involves a broken bone and an external wound that leads to the site of fracture.Fragments of bone commonly protrude through the skin.
In a comminuted fracture，the bone has broken or splintered into pieces.
An impacted fracture occurs when the bone is broken and one end is wedged into the interior of another bone.
An incomplete fracture occurs when the line of fracture does not completely transverse the entire bone.
A greenstick fracture is a break that does not extend through the entire thickness of the bone；that is，one side of the bone is broken and one side of the bone is bent.It occurs most often in children.The term greenstick refers to new branches on a tree that bend rather than break.(https://www.daowen.com)
A Colles fracture，a break at the lower end of the radius，occurs just above the wrist.It causes displacement of the hand and usually occurs as a result of flexing a hand to cushion a fall.
When a bone breaks，the fragmented bone ends must be brought back together into a straight line.Once the fracture is reduced，a splint or cast is often needed to immobilize the bone.A traction device like pulleys and weights may be attached to the skin or attached to the bone itself to maintain alignment of a fractured bone during healing.
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Task 4 Decide whether the following statements are true（T）or false（F）according to the text.
1.Fractures might result from car accidents，falls，or low bone density.（ ）
2.In a compound fracture，the skin integrity is uninterrupted.（ ）
3.In an impacted fracture，one end of the broken bone is embedded into the interior of another bone.（ ）
4.A greenstick fracture occurs more often in the elderly.（ ）
5.A splint or cast is often used to help keep an injured bone in place.（ ）