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What are Bone Cysts?

A bone cyst is a fluid-filled sac that develops within a bone. Bone cysts can occur in various bones throughout the body and are often benign (non-cancerous). They may vary in size and can be classified into different types based on their origin and characteristics.

Types of Bone Cysts

There are different types of bone cysts including: 

  • Unicameral Bone Cysts: They are also known as simple bone cysts and are commonly found in children and adolescents during periods of rapid growth. They are usually asymptomatic. 
  • Aneurysmal Bone Cysts: They are vascular bone lesions that can occur in both children and adults. These cysts contain blood-filled spaces and can cause bone expansion, thinning, and weakening, leading to a higher risk of pathological fractures. 
  • Non-Ossifying Fibromas: They are areas of fibrous tissue that form in the center of the bone. They are not painful and most of them resolve spontaneously. 
  • Fibrous Cortical Defects: They are benign fibrous lesions commonly found in the metaphyseal region of long bones in children and adolescents, which is a well vascularized region that is responsible for bone growth. 

Who is at Risk of Developing Bone Cysts?

Bone cysts can affect people of all ages, but they are most commonly found in children and adolescents during periods of rapid bone growth. Boys are more frequently affected than girls. Certain bone cysts may also be associated with genetic syndromes or other bone-related conditions.

What Causes a Bone Cyst?

The exact cause of bone cysts is not clear, but they may be related to problems with fluid drainage, blood vessels or bone growth. They are more common in children and teenagers, especially in the long bones of the arms and legs.

What are the Symptoms of a Bone Cyst?

Most bone cysts do not cause any symptoms and are discovered by chance during an X-ray for another reason. However, some bone cysts may cause pain, swelling, lump or fracture of the affected bone if they are large or located near a joint or a growth plate.

How is a Bone Cyst Diagnosed?

A bone cyst is usually diagnosed by an X-ray, which can show the location, size, and shape of the cyst. Sometimes, other imaging tests such as computed tomography (CT) scan or magnetic resonance imaging (MRI) may be needed to get more details. A biopsy, which involves taking a small sample of tissue from the cyst, may also be done to confirm the diagnosis and rule out other conditions.

How is a Bone Cyst Treated?

The treatment of a bone cyst depends on the type, size, and location of the cyst, as well as the age and general health of the person. Some bone cysts may heal on their own over time without any treatment. Others may need treatment to remove or drain the fluid from the cyst, or to fill the hole with bone graft or other material. This can be done by surgery or by injecting medicine into the cyst. The aim of treatment is to prevent fracture, infection, or recurrence of the cyst.

What is the Prognosis for a Bone Cyst?

The prognosis for a bone cyst depends on many factors, such as the type and size of the cyst, the response to treatment and the risk of complications. Most bone cysts are benign and do not affect the normal function of the bone. However, some bone cysts may recur after treatment or cause a fracture or infection of the affected bone.