Ring sequestrum causes:

Sequestrum is the dead bone separated out from the living bone by the granulation tissue. The factors responsible for bone death in chronic osteomyelitis are: raised intravascular pressure Vascular stasis and small vessel thrombosis periosteal stripping bacterial toxins Sequestrum is the hall mark of chronic osteomyelitis Ring sequestrum causes : Ring sequestrum * Amputation stump * Pin tract infection Cylindrical/pencil like Infants Green Pseudomonas osteomyelitis Black Amputation stump due to exposure of bone with air.