Bone cyst

An overview of bone cysts, their types, causes, and treatments

Bone cyst

A bone cyst is a fluid-filled cavity within a bone that can cause weakening of the bone structure. Bone cysts are often discovered incidentally on X-rays taken for other reasons, as they may not cause any symptoms. However, they can lead to pathological fractures if the bone becomes too weak.

X-ray image showing a bone cyst in the femur

Types of bone cysts

Bone cysts are generally classified into two main types:

Unicameral bone cyst

A unicameral bone cyst (UBC), also known as a simple bone cyst, is a benign, fluid-filled cavity that typically occurs in the long bones of children and adolescents. These cysts are most commonly found in the humerus and femur.

Aneurysmal bone cyst

An aneurysmal bone cyst (ABC) is a blood-filled cyst that can expand and cause bone destruction. Unlike unicameral bone cysts, aneurysmal bone cysts can occur in any bone and are more aggressive. They are often found in the spine and pelvis.

Causes

The exact cause of bone cysts is not well understood. Unicameral bone cysts are thought to result from a blockage in the bone marrow's blood supply, leading to fluid accumulation. Aneurysmal bone cysts may arise from a pre-existing lesion or trauma, but the precise mechanism is unclear.

Symptoms

Bone cysts often do not cause symptoms and are found incidentally. However, when symptoms do occur, they may include:

• Pain in the affected area
• Swelling
• Pathological fractures

Diagnosis

Bone cysts are typically diagnosed using imaging techniques such as X-ray, CT scan, or MRI. These imaging modalities help determine the size, location, and type of cyst.

Treatment

The treatment of bone cysts depends on the type and severity of the cyst. Options include:

• Observation: Small, asymptomatic cysts may be monitored with regular imaging.
• Aspiration and injection: Fluid can be aspirated from the cyst, and a corticosteroid or bone marrow can be injected to promote healing.
• Surgical curettage and bone grafting: For larger or symptomatic cysts, surgical removal of the cyst lining and filling the cavity with bone graft material may be necessary.

Prognosis

The prognosis for bone cysts is generally good, especially for unicameral bone cysts, which often resolve with treatment. Aneurysmal bone cysts may require more aggressive treatment and have a higher recurrence rate.

Related pages

• Bone tumor
• Pathological fracture
• Orthopedic surgery