Definition
aneurysmal bone cyst, benign bone aneurysm; a solitary
benign osteolytic lesion expanding a long bone or within a vertebra,
consisting of blood-filled spaces, and separated by fibrous tissue
containing multinucleated giant cells; such cyst's cause swelling,
pain, and tenderness.
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Radiographic Appearance
Radiographs:
-Radiolucent lesion w/ expanded cortex arising in medullary canal of
metaphysis, aneurysmal expanded appearance of cortex is contained by
periosteum & thin shell of bone;
Marked cortical thinning and erosion and periosteal elevation;
Lesion rarely penetrates the articular surface or growth plate;
Radiographic differential diagnosis includes:
simple bone cyst
giant cell tumor of bone
telangiectatic osteosarcoma
angiosarcoma.
Spine:
radiographs demonstrate loss of pedicle of involved vertebrae and
some displacement of
the soft tissues by the mass;
posterior elements of the vertebrae are a frequent location;
CT scan:
Look for fluid - fluid level (blood / serum);
fluid-fluid level may also be seen w/ telangiectatic osteosarcoma;
ABC has a density of about 20 hounsfield units;
Spine: CT scan shows a cystic lesion not appreciated on the
radiograph.
Bone Scan:
- shows intense uptake in the margin of the lesion, with normal
background
or decreased uptake in its center;
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Pathology
The Aneurysmal Bone
Cyst (ABC) is a type of bone tumor. This type of tumor is benign,
therefore it is not the type of disease that will spread to other
areas. However, a bone cyst can cause destruction of bone and
isolated symptoms at the site of the lesion. The most common problem
that a bone cyst will cause is weakening of the bone. This may lead
to increased susceptibility to fracture at that location. Because of
this, the bone cyst may need to be treated in the operating room to
prevent a fracture. Sometimes the bone cyst will not be found until
after a fracture has happened, this is called a pathologic fracture.
In this case, treatment of the fracture will also include treatment
of the bone cyst to prevent a recurrence of this problem
1. ABC predilects 10-25 years old individuals.
2. The most common locations include:
Posterior elements of the spine, Clavicle, Diaphysis of long bones
3. ABC commonly appears 6-12 months following trauma.
The most widely accepted pathogenetic mechanism of aneurysmal bone
cysts involves a local circulatory disturbance leading to markedly
increased venous pressure and the development of a dilated and
enlarged vascular bed within the affected bone area.
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Treatment
Curettage and bone
grafting has a 20-40% recurrence rate;
recurrance can be managed w/ more aggressive curettage or excision;
Marginal excision or wide excision w/ bone grafting is preferable;
In inaccessible areas, such as vertebrae, x-ray therapy is
effective;
With pathologic fracture successful resection may be difficult; |
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