It is the dense sclerotic bone surrounding the sequestrum. It has holes for the drainage of pus. Its cavity is lined by infected granulation tissue.

Ref: Ortho Maheshwari – p161

1. Sequestrum
2. Rhinitis caseosa – Epidemiology, Pathology, Clinical features, Treatment
3. Tension band principle
4. RGUHS Karnataka PGET 2011 – MCQ 84