What is a Sequestrum?
A
sequestrum is a fragment of necrotic bone that has become separated from the surrounding living bone tissue in the context of an infection or other pathological conditions. It is most commonly associated with
osteomyelitis, a severe bone infection.
Histological Features
When examining a sequestrum under a microscope, several distinctive histological features can be observed. The necrotic bone will appear dead and devoid of
osteocytes within the lacunae. The bone matrix may show areas of mineralization and possible fragmentation. Surrounding the sequestrum, there is often a zone of inflammatory cells, including
neutrophils,
lymphocytes, and
macrophages. This inflammatory response is part of the body’s effort to wall off and contain the infection.
Causes and Pathogenesis
The formation of a sequestrum typically follows an episode of acute or chronic osteomyelitis. Bacteria, such as
Staphylococcus aureus, can invade the bone, leading to an inflammatory response that increases intramedullary pressure. This pressure can compromise the blood supply to the bone, resulting in bone necrosis. Dead bone fragments then become separated from living bone, forming a sequestrum.
Clinical Implications
The presence of a sequestrum can complicate the treatment of osteomyelitis. Because it is avascular, it can act as a nidus for persistent infection, making it difficult for antibiotics to reach the affected area. Surgical intervention is often required to remove the sequestrum and debride the infected tissue. Failure to adequately address a sequestrum can result in chronic infection and other complications, including the formation of a
sinus tract or
pathological fractures.
Diagnosis
Diagnosis of a sequestrum involves both clinical examination and imaging studies.
X-rays can reveal areas of bone necrosis and sequestration, while
MRI or
CT scans may provide more detailed information about the extent of the infection and involvement of surrounding tissues. Histological examination of biopsy samples can confirm the presence of necrotic bone and the type of inflammatory cells involved.
Treatment
The mainstay of treatment for a sequestrum involves surgical removal, or
sequestrectomy. This procedure aims to excise the necrotic bone fragment and allow for the removal of infected material. In addition to surgery, long-term antibiotic therapy is often required to eradicate the underlying infection. Post-operative care may involve the use of bone grafts or other reconstructive techniques to restore the integrity of the bone.
Prognosis
The prognosis for patients with a sequestrum depends on several factors, including the extent of the infection, the presence of underlying conditions, and the timeliness and effectiveness of treatment. With appropriate surgical and medical management, many patients can achieve good outcomes. However, delayed treatment or inadequate removal of the sequestrum can lead to chronic osteomyelitis and other serious complications.Prevention
Preventing the formation of a sequestrum involves early recognition and treatment of bone infections. This includes prompt administration of appropriate antibiotics and, when necessary, surgical intervention to drain abscesses and debride infected tissue. Maintaining good hygiene and managing chronic conditions such as diabetes can also reduce the risk of developing osteomyelitis and subsequent sequestrum formation.
