Osteomyelitis

Osteomyelitis is infection of bone, caused by bacteria (most commonly Staphylococcus aureus), fungi, or occasionally mycobacteria. It can be hematogenous (blood-borne seeding, most common in children and elderly), contiguous (from an adjacent infection or open wound), or post-operative. Chronic osteomyelitis involves necrotic bone (sequestrum) and a surrounding envelope of reactive bone (involucrum), making eradication difficult without surgical debridement.

Risk factors include diabetes, peripheral vascular disease, immunosuppression, intravenous drug use, and prior fracture or surgery.

ESR and CRP are elevated (though non-specific). Blood cultures and wound cultures are obtained before antibiotic therapy when possible. X-rays are insensitive early; MRI is the most sensitive imaging modality and shows bone marrow edema and soft-tissue involvement. Nuclear medicine bone scan / labeled white cell scan helps when MRI is unavailable. Bone biopsy (CT-guided or open) is the gold standard for microbial diagnosis and antibiotic sensitivity.

Chronic osteomyelitis, hardware-associated infection, and acute osteomyelitis failing antibiotic therapy require surgical debridement. Hardware removal, dead space management (antibiotic cement, bone graft), and soft-tissue coverage are the cornerstones of treatment.

External patient-education references and related OSI pages for additional background:

• Britannica — Human skeleton
• AAOS OrthoInfo — patient education library
• OSI glossary — orthopedic terminology in plain language