Unicameral Bone Cyst: Symptoms, Causes, Treatment

What are the symptoms of a unicameral bone cyst?

A unicameral bone cyst, also known as a simple bone cyst, is a benign bone lesion typically found in children and adolescents. Its symptoms can vary, but commonly include:

• Pain: The cyst may cause localized pain, which can be dull or aching. In some cases, the pain might be intermittent and worsen with activity.
• Swelling: There may be swelling around the affected bone, although this is less common.
• Fractures: The cyst can weaken the bone, making it more susceptible to fractures, which may occur with minimal trauma.
• Restricted Movement: If the cyst is located near a joint, it might limit the range of motion or cause discomfort during movement.
• Asymptomatic: Many unicameral bone cysts are asymptomatic and are discovered incidentally on X-rays or other imaging studies done for other reasons.

The symptoms can depend on the cyst’s size, location, and whether it causes any weakening of the bone. If there are any concerns or symptoms, it’s important to consult a healthcare professional for a thorough evaluation and appropriate management.

What are the causes of a unicameral bone cyst?

The exact cause of a unicameral bone cyst (simple bone cyst) is not fully understood, but several theories have been proposed. Some possible causes include:

• Growth Plate Abnormalities: It is thought that a disruption in normal bone development or growth plate function could lead to the formation of a cyst. This could involve improper fluid drainage from bone, leading to fluid accumulation and cyst formation.
• Trauma: Although not a direct cause, a history of minor bone injury or trauma has been associated with the development of unicameral bone cysts in some cases. However, this relationship remains unclear.
• Vascular Blockage: Another theory suggests that a blockage in the blood supply to the bone, particularly during bone growth, could cause a cyst to develop due to fluid build-up.

While these are some suggested causes, the development of a unicameral bone cyst is generally considered idiopathic, meaning the exact cause is not known. These cysts are typically benign and are most often seen in growing bones of children and adolescents.

What is the treatment for a unicameral bone cyst?

Treatment for a unicameral bone cyst depends on factors such as the size of the cyst, its location, whether it is causing symptoms, and the risk of bone fractures. Common treatment options include:

• Observation: If the cyst is small, asymptomatic, and not at high risk of causing a fracture, doctors may recommend regular monitoring with X-rays. This is common for cysts found incidentally and in children who are still growing.
• Corticosteroid Injections: Injecting corticosteroids directly into the cyst can help reduce its size and promote healing. This treatment may need to be repeated over time.
• Bone Marrow or Bone Graft Injections: Injecting bone marrow aspirate or bone graft material into the cyst is another treatment option that can help promote bone healing.
• Surgical Curettage and Bone Grafting: For larger cysts or those causing fractures, surgical removal (curettage) of the cyst may be necessary. After removing the cyst, the cavity is often filled with bone graft material.
• Internal Fixation: In cases where the cyst has weakened the bone significantly, metal plates, screws, or rods may be used to stabilize the bone and prevent fractures.
• Fracture Management: If the cyst has already led to a fracture, the fracture will need to be treated first. This may involve immobilization or surgery, followed by treatment of the cyst.

Treatment aims to promote bone healing, prevent fractures, and reduce the risk of recurrence. Regular follow-ups are important as unicameral bone cysts can recur, especially in children and adolescents.