A 45-year-old diabetic man develops chronic osteomyelitis of the tibia following an open fracture. Sequestrum formation is noted on CT. The Cierny-Mader staging system classifies this as a Type III (localised) lesion. Which feature distinguishes Type III from Type IV (diffuse) osteomyelitis in this system?
- A Type III has no bone involvement, only periosteal reaction
- B Type III has full-thickness cortical involvement but the bone remains mechanically stable without through-and-through infection ✓
- C Type III affects only the medullary canal without cortical involvement
- D Type III always requires amputation, while Type IV is treated with debridement alone
Correct answer: B. Type III has full-thickness cortical involvement but the bone remains mechanically stable without through-and-through infection
Explanation
The Cierny-Mader system classifies osteomyelitis anatomically: Type I = medullary only; Type II = superficial cortical only; Type III = localised full-thickness cortical and medullary sequestrum but bone remains mechanically stable; Type IV = diffuse through-and-through infection with instability. The distinction is mechanical stability — Type III can be surgically managed by sequestrectomy and saucerisation while maintaining bone integrity, whereas Type IV requires skeletal stabilisation (e.g., external fixator or Ilizarov) in addition to debridement.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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