Osteomyelitis

Background

• Infection of the bone by bacteria or fungus
• Etiology
  • Contiguous spread (80%)
  • Hematogenous spread (20%)
    • More common in pediatric (long bones)
    • Less common in adults (spine)

Risk Factors

• Diabetic patients with one or more of the following:
  • Skin ulceration >2cm
  • Positive probe-to-bone test
  • ESR >70 (83-92% Sn)
  • Abnormal x-ray

Clinical Features

• Pain at the site
  • May also have warmth, swelling, erythema

Differential Diagnosis

Skin and Soft Tissue Infection

• Cellulitis
  • Hand cellulitis
  • Facial cellulitis
  • Orbital cellulitis
• Erysipelas
• Lymphangitis
• Folliculitis
• Hidradenitis suppurativa
• Skin abscess
  • Anorectal abscess
  • Bartholin gland abscess
  • Pilonidal abscess
  • Scrotal abscess
• Necrotizing soft tissue infections
  • Necrotizing fasciitis
  • Necrotizing myositis
  • Necrotizing cellulitis
  • Fournier's gangrene
• Mycobacterium marinum

Look-A-Likes

• Sporotrichosis
• Osteomyelitis
• Deep venous thrombosis
• Pyomyositis
• Purple glove syndrome
• Tuberculosis (tuberculous inflammation of the skin)

Evaluation

• X-ray
  • May be normal early in the course
  • Later will show bone demineralization, periosteal elevation, lytic lesions
  • Changes 10-21 days after infection
  • Sn 43-75%, Sp 75-83%
• Blood culture
• CT
  • Sn 67%, Sp 50%
• MRI is the standard for diagnosis (as early as 3-5 days after infection)
• Bone scan is sensitive, but lacks specificity vs. MRI

Management

Risk Factor	Likely Organism	Initial Empiric Antibiotic Therapy'
Elderly, hematogenous spread	MRSA, MSSA, gram neg	Vancomycin 1gm + (Piperacillin/Tazobactam 3.375 grams OR imipenem 500mg)
Sickle Cell Disease	Salmonella, gram-negative bacteria	Ceftriaxone 50mg/kg IV once daily OR Cefotaxime 50mg/kg IV three times daily, PLUS Vancomycin 15mg/kg IV four times daily OR Clindamycin 10mg/kg IV PO four times daily OR Nafcillin 50 mg/kg IV four times daily to cover K. Kingae (common in daycare population)
DM or vascular insufficiency	Polymicrobial: Staph, strep, coliforms, anaerobes	Vancomycin 1gm + (Piperacillin/Tazobactam 3.375 grams OR imipenem 500mg)
IV drug user	MRSA, MSSA, pseudomonas	Vancomycin 1gm
Newborn	MRSA, MSSA, GBS, Gram Negative	Vancomycin 15mg/kg load, then reduce dose, AND ceftazidime 30mg/kg IV q12 h
Children	MRSA, MSSA	Vancomycin 10mg/kg q6 h AND ceftazidime 50mg/kg q8hr
Postoperative (ortho)	MRSA, MSSA	Vancomycin 1gm
Human bite	Strep, anaerobes, HACEK organism	Piperacillin/Tazobactam 3.375gm OR imipenem 500mg
Animal bites	Pasteurella, Eikenella, HACEK organism	Piperacillin/Tazobactam 3.375gm OR imipenem 500mg
Foot puncture wound	Pseudomonas	Anti-pseudomonal, staph coverage

See Also

• Vertebral Osteomyelitis