Osteomyelitis

Osteomyelitis - Bone's Fiery Foes

• Bone & marrow inflammation, typically bacterial.
• Types:
  • Acute (<2 wks), Chronic (>2 wks).
  • Sources: Hematogenous, Contiguous, Direct Inoculation.

⭐ Staphylococcus aureus is the most common causative organism overall.

• Pathophysiology: Sequestrum (necrotic bone), Involucrum (new periosteal bone), Cloaca (draining sinus). Brodie's abscess (chronic, localized).
• Diagnosis:
  • Labs: ↑ESR, ↑CRP.
  • Imaging: MRI (best early detection & extent). X-ray (late: lytic changes, periostitis).
  • Gold Standard: Bone biopsy with culture & histology.
• Specific Organisms:
  • Sickle Cell Disease: Salmonella spp.
  • IV Drug Users: Pseudomonas aeruginosa, S. aureus.
  • Puncture wound (foot, through shoe): Pseudomonas aeruginosa.

Osteomyelitis - Spotting the Siege

• Bone infection (marrow & cortex). Routes: Hematogenous (kids: metaphysis), contiguous, direct implantation.
• Key Labs: ↑ ESR/CRP. MRI (most sensitive for early diagnosis). Bone biopsy (gold standard).

⭐ Brodie's abscess: A subacute or chronic localized osteomyelitis; appears as a well-circumscribed lytic lesion, often in the metaphysis of long bones (e.g., tibia), surrounded by a sclerotic rim on X-ray. Typically caused by S. aureus.

Osteomyelitis - Unmasking the Enemy

• Initial Clues:
  • Labs: ↑ ESR (>70mm/hr), ↑ CRP (acute phase, therapy response). Leukocytosis variable. Blood cultures (+ve ~50% hematogenous).
• Imaging Journey:
  • X-ray: First line. Early: soft tissue swelling. Later (10-14 days): periosteal reaction, lytic areas. Chronic: sequestrum, involucrum.
  • MRI:

    ⭐ MRI: most sensitive (>90%) & specific for early osteomyelitis (marrow edema, abscess in 1-2 days).

  • CT: Details cortical destruction, sequestra, sinus tracts.
  • Bone Scan (Tc-99m): Sensitive (↑ uptake), not specific; good for multifocal.
• Definitive Diagnosis:
  • Bone biopsy (image-guided/open): Gold standard. Tissue for culture (aerobic, anaerobic, fungal, AFB) & histopathology.

Osteomyelitis - Victory & Vigilance

• Therapeutic Goals: Infection eradication, pain relief, function restoration, recurrence prevention.
• Medical Therapy:
  • Prolonged antibiotics: Crucial. IV initially (e.g., Vancomycin + Ceftriaxone if MRSA suspected), then culture-guided oral.

  ⭐ Typical duration of antibiotic therapy for acute osteomyelitis is 4-6 weeks, can be longer for chronic.

• Surgical Strategy: Often mandatory for chronic/complicated cases.
  • Aggressive debridement: Removal of all infected/necrotic bone (sequestrectomy) & soft tissue.
  • Dead space management: Antibiotic-impregnated beads (PMMA), muscle flaps, bone grafts.
  • Stabilization: For pathological fractures or instability.
• Long-term Vigilance & Complications:
  • Chronic osteomyelitis, recurrence.
  • Pathological fracture.
  • Brodie's abscess.
  • Marjolin's ulcer (SCC in chronic sinus ⚠️).
  • Growth plate damage (children).

High‑Yield Points - ⚡ Biggest Takeaways

• Staphylococcus aureus: Most common organism in osteomyelitis.
• Children: Primarily hematogenous spread. Adults: Often contiguous source or direct inoculation.
• Brodie's abscess: A chronic, localized form of osteomyelitis.
• Hallmark signs: Sequestrum (dead bone fragment) and involucrum (new bone formation).
• MRI: Most sensitive for early diagnosis. Bone biopsy/culture: Gold standard.
• Treatment: Prolonged antibiotics (IV then oral) and surgical debridement if needed.
• Sickle cell disease: Increased risk of Salmonella osteomyelitis.