In chronic osteomyelitis, an involucrum refers to which structural feature, and what role does it play in dictating surgical management?

• A Dead cortical bone isolated from blood supply; its removal (sequestrectomy) is essential to eliminate infection
• B New periosteal bone forming a sleeve around the dead sequestrum; it provides structural support and must be preserved to prevent pathological fracture ✓
• C The fibrous tract connecting the bone abscess to the skin surface; its excision prevents recurrence
• D The zone of reactive sclerotic bone surrounding the Brodie's abscess; it prevents antibiotic penetration

Explanation

An involucrum is new reactive bone formed by the elevated periosteum around the necrotic segment (sequestrum) in chronic osteomyelitis. It acts as a biological splint, maintaining structural continuity even after the underlying cortex has become necrotic. Surgically, the involucrum must be assessed before sequestrectomy: if the involucrum is mature and well-formed, sequestrectomy can proceed safely; if immature or deficient, removal of the sequestrum may destabilise the limb and necessitate fixation. The sequestrum (dead bone) is option A; the sinus tract is option C; the sclerotic zone around Brodie's abscess is option D.

Reference: Maheshwari Essential Orthopaedics, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.