What Is a Simple Bone Cyst?

A unicameral bone cyst is known colloquially as a simple bone cyst. Simply, this is a fluid-filled lesion in the bone. It is typically more common in the long bones of children, but it can also occur in other types of bones and in adults. Depending on the severity of the cyst, it may cause symptoms or complications. Treatment often includes removal of the cyst.

A simple bone cyst occurs when fluid fills a hollow cavity in a bone. Serous fluid is the most common type of fluid found in the cavity, but blood may also be found in some cases. This cyst is typically surrounded by compressed fibrous tissue.

Long bones are the type of bones where simple bone cysts most commonly develop. It is most typical for simple bone cysts to be found in the bones of the upper arm, known as the humerus, and the bones in the thighs, known as the femurs. Additionally, this type of cyst tends to form in the metaphysis. This is the section of bone that is found where the long shaft of the bone connects with the end.

Children ages five to 15 are most commonly afflicted by these types of cysts. Older children and adults, however, may also be diagnosed with a simple bone cyst. These individuals, though, are more likely to develop the cyst in flat bones, including pelvic bones and ribs. It is also possible for a simple bone cyst to form in the jaw or heel bones in older individuals.

The cause of a simple bone cyst is usually not known. Some doctors, however, do have a few theories. Some believe that these cysts may be caused by a growth plate or circulation problem. There is also some evidence that repeated trauma, such as numerous broken bones, may also put a person at risk of developing a simple bone cyst.

Typically, a simple bone cyst is considered to be benign. This means that it does not usually affect any other location in the body besides the bone that contains it. In some cases, however, it may get larger. This can cause pressure to build up inside the bone and lead to a fracture, but this does not happen in every case.

There are usually no symptoms with a minor simple bone cyst. If a cyst begins to fracture the bone, however, an individual will typically feel some pain. Swelling may also be present in the area.

Unless it worsens and causes problems, a simple bone cyst will typically go undetected. These type of bone cysts are typically discovered using imaging tests, such as x-rays or computed topography scans. Steroid injections are sometimes used as a treatment for this condition, since they can cause the cyst to disappear. Other times, a small hole is made in the bone, and the cyst is removed. After this procedure, donor bone tissue is inserted to close the hole.