Maryam Sharifian

MSc student of O&P at Isfahan University Of

Medical science

Simple Bone Cyst (Unicameral)

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Discussion

a membrane lined cavity containing a clear yellow fluid.

occurrs most often in children 4-10 years of age;

lesions remain asymptomatic unless complicated by

fracture.

they enlarge during skeletal growth and become inactive,

or latent, after skeletal maturity.

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Active cysts

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Develop in patients under 10 years of age

• Cyst arises adjacent to growth plate & may grow to fill most of metaphysis

Bone may be slightly expanded within cortical shell

• May cause pathologic fracture

Passive cysts

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patients are usually over 12 years of age

cysts cease to expand

become increasingly separated from growth plate (more than 1-2 cm)

have thicker bony wall than active lesions

may show evidence of healing or ossification

less likely to result in fx

Causes…

The cause of a unicameral bone cyst remains unknown.

Theories have been proposed but none have been definitively

proven.

One of these theories is that the cysts result from a disorder

of the growth plate.

Another is that the cysts result from problems with

circulation that are caused by a developmental anomaly in the

veins of the affected bone.

The role trauma plays in the development of these cysts is

unknown.

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Symptoms…

Unless there has been a fracture, bone cysts are without

symptoms.

They may occasionally be discovered by chance on x-rays

obtained for other reasons.

There is no mass or tenderness unless there is a fracture.

There may be an abnormal angulation of the limb secondary

to the fracture or shortening of the limb if the adjacent

growth plate is involved.

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Location

lesion appears to arise from the growth plate & in early stages, lesion is lies adjacent to growth plate;

• typically the simple bone cyst will have a central location, whereas an ABC will have a slightly eccentric location;

- predilection for the metaphysis of long bones;- proximal humerus (50% of cases)- proximal tibia- proximal femur (40%)- foot:Calcaneal Bone Cysts

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Radiographs

show a central, well marginated & symmetric radiolucent defect in metaphysis

metaphyseal bone does not remodel normally

metaphysis is broader than normally seen but not broader than with width of epiphyseal plate

thin rim of non reative bone borders the unicameral bone cyst

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Radiography

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Differential Diagnosis

• Monostotic fibrous dysplasia is usually eccentric rather than central and diaphysealrather than metaphyseal

• Periosteal reaction is greater in fibrous dysplasia than simple bone cyst;

Fibrous dysplasia

• Enlarge metaphysis to greater than width of the epiphyseal plate;

Aneurysmalbone cyst

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Histologic Examination

Active cyst have a mesothelial membrane lining thin margin of bone

Inner wall of bone adjacent to membrane may be lined by osteoclasts

Between membrane & osteoclasts is a layer of areolar tissue containing fibroblastic and multinucleated giant cells

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Treatment

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• Goal of treatment is prevention of pathologic fracture

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• Simple cysts are treated with curettage and bone grafting

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• Recurrence is high for active cysts (50%) & low for latent cysts (10%)

Thank you

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