things, and pull into a standing position. By 14
months most infants are walking on their own,
and by 18 months can run and jump. Motor
skills—the ability to use the musculoskeletal sys-
tem for mobility—continue to evolve throughout
childhood. These skills, along with muscle mass
and BONE DENSITY, peak in the late 20s.
By age 40, musculoskeletal structures and func-
tions begin to decline. Joints begin to show the
effects of wear. One health consequence of this is
OSTEOARTHRITIS, which can become severe enough
to warrant JOINT REPLACEMENT. Softening of the lig-
aments and other connective tissues makes joints
more vulnerable to injury. Muscle mass and bone
density gradually decrease, as does strength and
FLEXIBILITY. In women these decreases become dra-
matic with MENOPAUSE, with the sudden and signif-
icant decline in estrogen. (Estrogen is one of the
hormones that influences the movement of cal-
cium between the BLOOD circulation and the
bones.) The rate of decrease remains fairly con-
stant in men, who have inherently larger amounts
of muscle and bone.
However, by about age 75 or 80 gender differ-
ences balance out. Men and women alike have
significantly less muscle tissue and bone structure,
increasing susceptibility to injury from falls and
other accidents. Though bone remodeling contin-
ues, it proceeds at a much slower pace. Other
changes in the body may result in bone resorption
outpacing bone rebuilding. The risk for neuromus-
cular disorders such as PARKINSON’S DISEASEalso
rises. At age 80, a woman may have lost four
inches or more of her height as a consequence of
musculoskeletal changes. Men also lose height,
though typically not as dramatically.
See also ACCIDENTAL INJURIES; AGING, NEUROLOGIC
CHANGES THAT OCCUR WITH; ESTROGENS; HIP FRACTURE
IN OLDER ADULTS; HORMONE; LIGAMENT; RHEUMATOID
ARTHRITIS.
amputation Removal or loss of a limb or body
part. Amputation may be surgical, in which the
removal is intentional to treat a disease condition,
or traumatic, in which accidental injury results in
the loss of the body part. Most amputations
involve digits (fingers and toes) and limbs. In the
United States, complications of DIABETESaccount
for the majority of surgical amputations of the foot
and lower leg; traumatic injury accounts for most
upper extremity amputations. Other causes of
amputation include uncontrollable OSTEOMYELITIS
(INFECTIONof the BONE), severe PERIPHERAL VASCULAR
DISEASE(PVD), and tumors.
US surgeons perform nearly 200,000 amputa-
tions each year. Surgical amputation is a treat-
ment of last resort, becoming an option only
when other treatments fail and leaving the limb
threatens the person’s health. Surgical amputation
is a major OPERATIONperformed in a hospital. For
most amputations the person stays 2 to 10 days in
the hospital.Surgical Procedure
With the person asleep under general ANESTHESIA,
the surgeon cuts through the SKINand MUSCLEto
reach the bone, structuring the incisions so tissue
remains to create a flap that covers the surgical
wound. The surgeon may need to use a saw to cut
the bone, though in some circumstances the
amputation takes place at the JOINT(called a disar-
ticulation). For limb amputation the surgeon
shapes the bone ends and remaining tissue to sup-
port a prosthesis.
When there is no infection or risk for infection
is minimal, the surgeon closes the surgical wound
by suturing the muscles together around the bone
and pulling tissue and skin over the end in a flap.Risks and Complications
The primary risks of amputation are excessive
bleeding during surgery and infection and poor
HEALING after surgery. The risk for infection is
highest in people who have problems with BLOOD
circulation in the extremities, such as may occur
in PVD or diabetes. People who have diabetes may
be slow to heal from the surgery of amputation,
usually an extension of the complications of dia-
betes that made necessary the limb amputation.
Complications such as failure to heal or spreading
GANGRENE(dead tissue) require a follow-up surgery
to attempt to improve the surgical wound for bet-
ter healing.Outlook and Lifestyle Modifications
Recovery and limitations depend on the type of
amputation and the underlying health conditions.
With focused PHYSICAL THERAPYand OCCUPATIONAL300 The Musculoskeletal System