Osteomyelitis
INTRODUCTION
Background: Osteomyelitis is an acute or chronic inflammatory process of the
bone and its structures secondary to infection with pyogenic organisms.
Pathophysiology: The infection associated with osteomyelitis may be localized
or it may spread through the periosteum, cortex, marrow, and cancellous tissue.
The bacterial pathogen varies on the basis of the patient's age and the
mechanism of infection.
The following are the 2 primary categories of acute osteomyelitis:
Hematogenous osteomyelitis is an infection caused by bacterial seeding from the
blood. Acute hematogenous osteomyelitis is characterized by an acute infection
of the bone caused by the seeding of the bacteria within the bone from a remote
source. This condition occurs primarily in children. The most common site is the
rapidly growing and highly vascular metaphysis of growing bones. The apparent
slowing or sludging of blood flow as the vessels make sharp angles at the distal
metaphysis predisposes the vessels to thrombosis and the bone itself to
localized necrosis and bacterial seeding. Acute hematogenous osteomyelitis,
despite its name, may have a slow clinical development and insidious onset.
Direct or contiguous inoculation osteomyelitis is caused by direct contact of the
tissue and bacteria during trauma or surgery. Direct inoculation (contiguous-
focus) osteomyelitis is an infection in the bone secondary to the inoculation of
organisms from direct trauma, spread from a contiguous focus of infection, or
sepsis after a surgical procedure. Clinical manifestations of direct inoculation
osteomyelitis are more localized than those of hematogenous osteomyelitis and
tend to involve multiple organisms.
Additional categories include chronic osteomyelitis and osteomyelitis secondary
to peripheral vascular disease. Chronic osteomyelitis persists or recurs,
regardless of its initial cause and/or mechanism and despite aggressive
intervention. Although listed as an etiology, peripheral vascular disease is
actually a predisposing factor rather than a true cause of infection.
Disease states known to predispose patients to osteomyelitis include diabetes
mellitus, sickle cell disease, acquired immune deficiency syndrome (AIDS), IV
drug abuse, alcoholism, chronic steroid use, immunosuppression, and chronic
joint disease. In addition the presence of a prosthetic orthopedic device is an
independent risk factor as is any recent orthopedic surgery or open fracture.
Frequency:
In the US: The overall prevalence is 1 per 5,000 children. Neonatal
prevalence is approximately 1 per 1,000. The annual incidence in sickle
cell patients is approximately 0.36%. The prevalence of osteomyelitis after
foot puncture may be as high as 16% (30-40% in patients with diabetes).
Internationally: The overall incidence is higher in developing countries.
Mortality/Morbidity:
Morbidity can be significant and can include localized spread of infection
to associated soft tissues or joints; evolution to chronic infection, with pain
and disability; amputation of the involved extremity; generalized infection;
or sepsis. Up to 10-15% of patients with vertebral osteomyelitis will
develop neurologic findings or frank spinal-cord compression.
Mortality rates are low, unless associated sepsis or an underlying serious
medical condition is present.
Sex: Male-to-female ratio is approximately 2:1.
Age: In general, osteomyelitis has a bimodal age distribution.
Acute hematogenous osteomyelitis is primarily a disease in children.
Direct trauma and contiguous focus osteomyelitis are more common
among adults and adolescents than in children.
Spinal osteomyelitis is more common in persons older than 45 years.
CLINICAL
History: Hematogenous osteomyelitis usually presents with a slow insidious
progression of symptoms. Direct osteomyelitis generally is more localized, with
prominent signs and symptoms. General symptoms of osteomyelitis include the
following:
Hematogenous long-bone osteomyelitis
o Abrupt onset of high fever (fever is present in only 50% of neonates
with osteomyelitis)
o Fatigue
o Irritability
o Malaise
o Restriction of movement (pseudoparalysis of limb in neonates)
o Local edema, erythema, and tenderness
Hematogenous vertebral osteomyelitis
o Insidious onset
o History of an acute bacteremic episode
o May be associated with contiguous vascular insufficiency
o Local edema, erythema, and tenderness
Chronic osteomyelitis
o Nonhealing ulcer
o Sinus tract drainage
o Chronic fatigue
o Malaise
Physical: Findings at physical examination may include the following:
Fever (present in only 50% of neonates)
Edema
Warmth
Fluctuance
Tenderness to palpation
Reduction in the use of the extremity (eg, reluctance to ambulate, if the
lower extremity is involved or pseudoparalysis of limb in neonates)
Sinus tract drainage (usually a late finding or one that occurs with chronic
infection)
Causes: Bacterial causes of acute and direct osteomyelitis include the following:
Acute hematogenous osteomyelitis
o Newborns (younger than 4 mo): S aureus, Enterobacter species,
and group A and B Streptococcus species
o Children (aged 4 mo to 4 y): S aureus, group A Streptococcus
species, Haemophilus influenzae, and Enterobacter species
o Children, adolescents (aged 4 y to adult): S aureus (80%), group A
Streptococcus species, H influenzae, and Enterobacter species
o Adult: S aureus and occasionally Enterobacter or Streptococcus
species
Direct osteomyelitis
o Generally: S aureus, Enterobacter species, and Pseudomonas
species
o Puncture wound through an athletic shoe: S aureus and
Pseudomonas species
o Sickle cell disease - S aureus and Salmonellae species
DIFFERENTIALS
Cellulitis
Gas Gangrene
Gout and Pseudogout
Hand Infections
Neoplasms, Spinal Cord
Pediatrics, Limp
Pediatrics, Sickle Cell Disease
Spinal Cord Infections
Other Problems to be Considered:
Fractures
Aseptic bone infarction
Neuropathic joint disease
