In chronic osteomyelitis with a sequestrum and involucrum, which term describes the natural opening through the involucrum that allows discharge of pus and sequestrum to the surface?
- A Brodie's abscess
- B Sinus tract
- C Cloaca ✓
- D Erosion channel
Correct answer: C. Cloaca
Explanation
Cloaca is the anatomical opening (hole) in the involucrum (periosteal new bone shell) through which pus and dead bone fragments (sequestrum) discharge to form a sinus tract. The sequestrum is avascular dead bone within the infection cavity; the involucrum is living reactive bone surrounding it. Brodie's abscess is a subacute localised intraosseous cavity. A sinus tract is the external opening on the skin, not the opening in the bone itself.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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