Unicameral bone cysts (UBCs), also known as simple bone cysts, are fluid-filled cavities that develop within bones, most commonly in children and adolescents. While many unicameral bone cysts remain asymptomatic and are discovered incidentally, they can lead to several complications that affect bone integrity and function.
One of the primary complications of unicameral bone cysts is **pathological fracture**. Because the cyst creates a weakened area within the bone, even minor trauma or normal activity can cause the bone to break at the site of the cyst. This is especially common in weight-bearing bones such as the femur or humerus. Pathological fractures often present suddenly with pain and swelling and may be the first sign that a cyst is present.
Another significant complication is **bone deformity**. If the cyst grows or persists over time, it can cause thinning and expansion of the bone cortex (the hard outer layer of bone), leading to structural weakness and deformity. This can affect the shape and strength of the bone, potentially impairing normal function or growth, especially in children whose bones are still developing.
**Recurrence** is also a concern after treatment. Even after surgical intervention such as curettage (scraping out the cyst) and bone grafting, unicameral bone cysts can recur, necessitating further treatment. Recurrence rates vary depending on the treatment method and the cyst’s location.
In some cases, the cyst may cause **joint problems** if it is located near a joint surface. The cyst can erode the subchondral bone (the bone just below the cartilage), potentially leading to joint instability, pain, or early degenerative changes. This is more likely if the cyst extends close to or into the joint space.
Rarely, **infection** can complicate a unicameral bone cyst, especially if there has been prior surgery or an open fracture. Infection within the cyst or surrounding bone (osteomyelitis) can cause severe pain, swelling, fever, and may require aggressive antibiotic treatment and surgical drainage.
Chronic pain and swelling can also occur, either from the cyst itself or from complications such as fracture or infection. Persistent symptoms may impact mobility and quality of life.
In summary, the main complications of unicameral bone cysts include:
– **Pathological fractures** due to weakened bone structure
– **Bone deformity** from cyst expansion and cortical thinning
– **Recurrence** after treatment requiring additional interventions
– **Joint involvement** causing pain or instability if near joint surfaces
– **Infection**, though rare, can cause serious local and systemic issues
– **Chronic pain and swelling** impacting function
These complications highlight the importance of careful monitoring and appropriate management of unicameral bone cysts to minimize risks and preserve bone health.
