by Robert C. Mellors, M.D., Ph.D.
III. Bone Infections
1. General Considerations
Osteomyelitis (literally an inflammation of bone and bone marrow) is the
generic term for bone infections. Pathogenic microorganisms (pyogenic
bacteria, mycobacteria, fungi) can spread to bone by one of three
routes: hematogenous spread; direct extension from a contiguous site of
infection; and direct introduction. The most serious bone infections are
pyogenic osteomyelitis and tuberculosis; also to be noted are rare cases
of syphilis and fungus infections. The clinical course of
osteomyelitis depends on the characteristics of the causative organism,
the route of the infection, and the age of the patient.
2. Hematogenous (Pyogenic) Osteomyelitis
3. Osteomyelitis from a Contiguous Infection
Burns, sinus disease, peridontal infection, soft tissue infection, and
skin ulcers caused by peripheral vascular disease (arteriosclerosis,
diabetes, vasculitis) are among the adjoining sites of microbial
infection that may spread to bone. The onset is often insidious, and the
symptoms are those of infection and inflammation of the involved bone.
The pathological and radiological changes are similar to those seen in
chronic hematogenous osteomyelitis. The treatment usually requires
surgical intervention (debridement of necrotic tissue, drainage of
abscesses, etc.) combined with bacteriological cultures and appropriate
antimicrobial therapy. Blood cultures are positive in about 10% of
4. Osteomyelitis from an Introduced Infection
Penetrating wounds, compound fractures, simple fractures treated
surgically with open reduction and internal fixation, prosthetic joint
replacements, and other orthopedic appliances (plates, nails, screws,
pins) may introduce microbial infection directly into bone. The
pathological changes in the involved bone include suppurative
inflammation, ischemic necrosis, fibrosis, and reactive new-bone
formation as occur in hematogenous osteomyelitis.
5. Bone Tuberculosis
6. Bone Syphilis
7. Fungus Infections of Bone
Mycotic osteomyelitis is rare and usually occurs from the spread of a
contiguous infection of soft tissue or sometimes by hematogenous
spread. The fungus diseases most often reported as a cause of skeletal
infection are coccidioidomycosis (San Joaquin Valley Fever),
actinomycosis, blastomycosis, cryptococcosis, and sporotrichosis.
769: Coccidioidomycosis of bone (vertebra), H&E.
628: Actinomycosis of bone. H&E.