Chronic discharging sinus with bone paicle is seen in-

In chronic ostemoylelitis bone is destroyed in the affected pa Cavities containing pus and pieces of dead bone are surrounded by vascular tissue. Often sinus track leads to skin surface, the sinus tends to heal and present down reverently but if a sequestrum is present it never heals permanently This is because sequestra act as substrate for bacterial adhesion in much the same way as foreign implants, ensuring the persistence of infection until they are removed or discharged through perforation in the involucrum and sinuses that drain to the skin REF : MAHESWARI 9TH ED