Sequestrum

A sequestrum is a piece of dead bone that has become separated during the process of necrosisfrom 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 intramedullarypressure due to inflammatory exudates
• the periosteumbecomes 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 canalsbecome 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 bloodtream, poorly penetrate these tissues. Hence the difficulty in treating chronic osteomyelitis.

At the same time as this, new bone is forming (known as involcrum). Opening in this involcrum allow debris and exudates (including pus) to pass from the sequestrum via sinuses to the skin.

This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Sequestrum Wikipedia article Sequestrum.