Health Dictionary
Reliable, easy-to-read patient information on common medical conditions — written in plain language, free of jargon, and grounded in current evidence. Browse the most frequent diagnoses, understand what they mean for everyday life, and learn which steps and questions help you have a focused conversation with your doctor.
Sequestrum
Introduction
A sequestrum is a piece of dead bone that has become separated during the process of necrosis from normal/sound bone.
It is a complication (sequelae) of osteomyelitis. The pathological process is as follows:
- infection in the bone leads to an increase in intramedullary pressure due to inflammatory exudates
- the periosteum becomes stripped from the osteum, leading to vascular thrombosis
- bone necrosis follows due to lack of blood supply
- sequestra are formed
The sequestra are surrounded by sclerotic bone which for all intents and purposes is relatively avascular (without a blood supply). Within the bone itself, the haversian canals become blocked with scar tissue, and the bone becomes surrounded by thickened periosteum.
Due to the avascular nature of this bone, antibiotics which travel to sites of infection via the bloodstream, poorly penetrate these tissues. Hence the difficulty in treating chronic osteomyelitis.
At the same time as this, new bone is forming (known as involucrum). Opening in this involucrum allow debris and exudates (including pus) to pass from the sequestrum via sinus tracts to the skin.