Osteomyelitis

A post-op patient develops deep bone pain, fever, and elevated WBC two weeks after an open fracture repair. The infection isn't in the wound — it's in the bone itself, and delayed recognition leads to limb loss.

Osteomyelitis is infection of the bone, most commonly caused by Staphylococcus aureus. It reaches bone through three routes: hematogenous spread (bloodstream seeding, common in children), contiguous spread from adjacent soft-tissue infection or open fracture, and direct inoculation during surgery or trauma. The hallmark presentation is localized bone pain that is constant, deep, and worsens despite analgesics, accompanied by fever, erythema, warmth, and swelling over the affected area. Elevated WBC, ESR, and CRP confirm systemic inflammation, but the definitive diagnostic marker is bone biopsy with culture. MRI is the most sensitive imaging study. Blood cultures are drawn before antibiotics begin. Treatment requires prolonged IV antibiotic therapy — typically 4 to 6 weeks via a PICC line. Surgical debridement removes necrotic bone (sequestrum). If chronic osteomyelitis develops, the involucrum (new bone shell around dead bone) may need surgical intervention. Nursing priorities include strict aseptic wound care, monitoring the IV access site, assessing neurovascular status distal to the infection, and managing pain. Immobilization of the affected extremity reduces pathologic fracture risk.

Key Distinctions

Don't confuse osteomyelitis (bone infection with deep constant pain and fever) with cellulitis (soft-tissue infection without bone involvement on MRI). Students mix up sequestrum (dead bone fragment harboring bacteria) and involucrum (new bone forming around dead bone) — sequestrum must be removed surgically. Osteomyelitis requires weeks of IV antibiotics, unlike most soft-tissue infections that respond to shorter oral courses.

Clinical Pearl

Sequestrum is the 'skeleton in the closet' — dead bone hiding bacteria that antibiotics can't reach. If it stays, the infection never clears.