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Musculoskeletal Function
to form devascularized fragments, called
sequestra.
18,19
Eventually, the purulent drainage may penetrate the
periosteum and skin to form a draining sinus. In children
1 year of age and younger, the adjacent joint is often
involved because the periosteum is not firmly attached
to the cortex.
18,19
From 1 year of age to puberty, subperi-
osteal abscesses are more common. As the process con-
tinues, periosteal new bone formation and reactive bone
formation in the marrow tend to wall off the infection.
In adults, the long bone microvasculature no lon-
ger favors seeding, and hematogenous infection rarely
affects the appendicular skeleton. Instead, vertebrae,
sternoclavicular and sacroiliac joints, and the symphy-
sis pubis are involved. Infection typically first involves
subchondral bone, then spreads to the joint space. With
vertebral osteomyelitis, this causes sequential destruc-
tion of the endplate, adjoining disk, and contiguous ver-
tebral body. Infection less commonly begins in the joint
and spreads to the adjacent bone.
The signs and symptoms of acute hematogenous
osteomyelitis are those of bacteremia accompanied
by symptoms referable to the site of the bone lesion.
Bacteremia is characterized by chills, fever, and malaise.
There often is pain on movement of the affected extrem-
ity, loss of movement, and local tenderness followed by
redness and swelling. X-ray studies may appear normal
initially, but they show evidence of periosteal elevation
and increased osteoclast activity after an abscess has
formed. Radiographic bone scans and MRI can usually
detect subtle changes at an earlier stage.
The treatment of hematogenous osteomyelitis begins
with identification of the causative organism through
blood and bone aspiration cultures. Antimicrobial agents
are given first parenterally and then orally. The length of
time the affected limb needs to be rested and the pain con-
trol measures used are based on the person’s symptoms.
Débridement and surgical drainage also may be necessary.
Chronic Osteomyelitis.
Chronic osteomyelitis usually
occurs in adults and is secondary to an open wound,
most often to the bone or surrounding tissue. It may be
the result of delayed or inadequate treatment of acute
hematogenous osteomyelitis or osteomyelitis caused
by direct contamination of bone by exogenous organ-
isms. Chronic osteomyelitis can persist for years; it may
appear spontaneously following a minor trauma, or
when resistance is lowered.
The hallmark feature of chronic osteomyelitis is the
presence of infected dead bone, a
sequestrum,
that has
separated from the living bone.
8,18,19
A sheath of new
bone, called the
involucrum,
forms around the dead
bone. Radiologic techniques such as x-ray films, bone
scans, and sinograms are used to identify the infected
site. Chronic osteomyelitis or infection around a total
joint prosthesis can be difficult to diagnose because the
classic signs of infection are not apparent and the blood
leukocyte count may not be elevated. A subclinical infec-
tion may exist for years. Bone scans are used with bone
biopsy for a definitive diagnosis.
The treatment of chronic bone infections begins with
wound cultures to identify the microorganism and its
sensitivity to antibiotic therapy.
31–33
Initial antibiotic
therapy is often followed by surgery to remove foreign
bodies (e.g., metal plates, screws) or sequestra and by
long-term antibiotic therapy. Immobilization of the
affected part usually is necessary, with restriction of
weight bearing on a lower extremity. External fixation
devices are sometimes used.
Direct Penetration and Contiguous Spread
Osteomyelitis.
Direct penetration or extension of bac-
teria from an outside (exogenous) source is now the most
common cause of osteomyelitis in the United States.
19
Bacteria may be introduced directly into the bone by
a penetrating wound, an open fracture, or surgery. In
persons with vascular insufficiency or poorly controlled
diabetes, osteomyelitis may develop from a skin lesion.
Iatrogenic bone infections are those inadvertently
brought about by surgery or other treatments. These
complications include pin tract infection in skeletal trac-
tion, septic (infected) joints in joint replacement sur-
gery, and wound infections after surgery. Risk factors
for the development of a surgical site infection include
both host factors and those related to the procedure.
34
Delays in wound healing, infection and failure of surgi-
cal implants cause greater morbidity and possibly the
need for subsequent revision surgery.
Osteomyelitis after trauma or bone surgery usually is
associated with persistent or recurrent fever, increased
pain at the operative or trauma site, and poor incisional
healing, which often is accompanied by continued
wound drainage and wound separation. Prosthetic joint
infections often present with joint pain, fever, and cuta-
neous drainage.
Treatment includes the use of antibiotics and selective
use of surgical interventions. The choice of agents and
method of administration depend on the microorganisms
causing the infection. In acute osteomyelitis that does not
respond to antibiotic therapy, surgical decompression
is used to release intramedullary pressure and remove
drainage from the periosteal area. Prosthesis removal
may be necessary in cases of an infected prosthetic joint.
The joint is left out while a 2- to 6-week course of ther-
apy is given, after which another joint is implanted.
32
Tuberculosis Osteomyelitis
A resurgence of tuberculosis osteomyelitis is occurring in
industrializedcountries of theworld, attributed to the influx
of immigrants from developing countries and the greater
numbers of immunocompromised people.
19
Tuberculosis
can spread from one part of the body, such as the lungs
or the lymph nodes, to the musculoskeletal system. Any
bone, joint, or bursa may be affected, but the spine is the
most common site, followed by the knees and hips.
18,19,35
Tubercular osteomyelitis tends to be more destructive and
difficult to control than pyogenic osteomyelitis. The infec-
tion spreads through large areas of the medullary cavity
and causes extensive necrosis. In tuberculosis of the spine,
also known as
Pott disease,
the infection spreads through
the intervertebral disks to involve multiple vertebrae and
extends into the soft tissue, forming abscesses.
