111BOX6–1 FRACTURES AND THEIR REPAIR
Box Figure 6–A Types of fractures. Several types of
fractures are depicted in the right arm.A fracture means that a bone has been broken.
There are different types of fractures classified as to
extent of damage.
Simple (closed)—the broken parts are still in nor-
mal anatomic position; surrounding tissue damage
is minimal (skin is not pierced).
Compound (open)—the broken end of a bone
has been moved, and it pierces the skin; there may
be extensive damage to surrounding blood vessels,
nerves, and muscles.
Greenstick—the bone splits longitudinally. The
bones of children contain more collagen than do
adult bones and tend to splinter rather than break
completely.
Comminuted—two or more intersecting breaks
create several bone fragments.
Impacted—the broken ends of a bone are forced
into one another; many bone fragments may be
created.
Pathologic (spontaneous)—a bone breaks with-
out apparent trauma; may accompany bone disor-
ders such as osteoporosis.
The Repair Process
Even a simple fracture involves significant bone
damage that must be repaired if the bone is to
resume its normal function. Fragments of dead or
damaged bone must first be removed. This is
accomplished by osteoclasts, which dissolve and
reabsorb the calcium salts of bone matrix. Imagine
a building that has just collapsed; the rubble must
be removed before reconstruction can take place.
This is what the osteoclasts do. Then, new bone
must be produced. The inner layer of the perios-
teum contains osteoblasts that are activated when
bone is damaged. The osteoblasts produce bone
matrix to knit the broken ends of the bone
together.
Because most bone has a good blood supply, the
repair process is usually relatively rapid, and a sim-
ple fracture often heals within 6 weeks. Some parts
of bones, however, have a poor blood supply, and
repair of fractures takes longer. These areas are the
neck of the femur (the site of a “fractured hip”) and
the lower third of the tibia.
Other factors that influence repair include the
age of the person, general state of health, and
nutrition. The elderly and those in poor health often
have slow healing of fractures. A diet with sufficient
calcium, phosphorus, vitamin D, and protein is also
important. If any of these nutrients is lacking, bone
repair will be a slower process.