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Sequestrum is a bone disorder that occurs when a fragment of dead bone separates from living bone, usually as a consequence of injury or disease. The process by which the dead bone is cast off is called necrosis, and it results in the loss of tissue. Necrosis of bones takes place after a bone fragment dies and then separates. Although sequestrum causes separation of dead bone from living bone, dead bone often remains either partly encased or in close contact with newly formed bone, causing a sinus, or a narrow cavity.
There normally are 206 bones in the human body, all of which serve one or more of three main functions. Some bones, such as the skull and ribcage, function to form a protective barrier around certain structures and organs. Other bones, such as the spine, act to support weight and posture. Specific bones are also involved in movement. These include bones found in the feet, hips and hands.
Bone is not a permanent structure in the body. It is a living and dynamic organ that is constantly adapting to mechanical, chemical and external influences. It is the body’s largest store of calcium and phosphate — minerals that are vital to numerous bodily processes.
Like all other organs in the body, bones are susceptible to disease. Sequestrum is one of many bone disorders, and it is the death of a bone or cell resulting in tissue damage. This bone disorder can occur because of infections such as osteomyelitis or injuries such as bone fractures. Sequestrum takes place in localized regions of the body.
Necrosis is the secondary process to cell death, resulting in tissue loss. This process is commonly a consequence of traumatic injury, bacterial infections or a condition called ischemia. The term "ischemia" refers to bloodlessness or a lack of circulation to a particular part of the body. Bloodlessness can occur as a result of a spasm, contraction or blocking of the arteries, also known as thrombosis.
It usually is about 12 hours after the death of a bone or cell body that tissue damage or necrosis begins to occur. In these earliest stages, there are no symptoms. When symptoms do begin, they usually appear in the form of pain, decreased movement and the possible development of gangrene as a consequence of decreased blood supply. Damage to tissue is permanent, and treatment is used to prevent further bone loss and tissue death, rather than to cure the condition entirely.