Pathoanatomy—bony infection caused by microbial invasion characterized by inflammation and destruction of bone

Mechanism—contiguous spread (abscess, septic joint), direct inoculation (trauma, surgery, foreign body), or indirect (hematogenous seeding)

Epidemiology—24 cases per 100 000 person-years, more male patients than female, greater incidence with age, occurs more in lower extremity than in upper extremity, 1% to 6% of all hand infections involve bone, most often in the distal phalanx

Risk factors include recent surgery or trauma, IV drug use, immune deficiency/suppression, diabetes, vascular insufficiency.

History—pain, fever, chills, fatigue, exposure to risk factors

Physical examination—tenderness, erythema, edema, warmth, fluctuance, exposed bone, sinus tract (Figure 50.1)

Laboratory studies—elevated white blood cell count, erythrocyte sedimentation rate, and C-reactive protein (lack specificity), positive blood cultures in 50% of cases; laboratory findings can be normal in osteomyelitis of the small bones of the hand and wrist

Imaging—Radiograph (Figure 50.2) (lytic lesion, surrounding sclerosis, periosteal thickening) may not show changes for 2 weeks, MRI positive up to 90% sensitivity and specificity (distinguish between soft tissue and bone infection), CT scan is rarely used in diagnosis (may be helpful for guided needle biopsy)

Classification—acute (within 2 weeks), subacute (between 2 weeks and several months), and chronic (after several months); 10% to 30% acute turn chronic; chronic osteomyelitis characterized by sequestrum (necrotic bone) and involucrum (new bone formation)