Aneurysmal Bone Cysts

  • What are aneurysmal bone cysts?

    An aneurysmal bone cyst is a benign blood-filled cyst in the bone that tends to expand or grow. While it is a cyst (a sac) it does have a thin bony wall surrounding the growth, so it is sometimes called a bony tumor. Even though it is not cancerous, aneurysmal bone cysts grows aggressively, so they must be removed.

    Aneurysmal bone cysts (ABCs) can occur in the vertebral column as well as the extremities, usually occurring in people age 20 or younger. ABCs can also occur in the rib cage.

    About half of patients with aneurysmal bone cysts of the spine are children; most discover the cyst in their teen years. While ABCs are the second-most common tumors in children, they are rare and account for only 1-6 percent of bony tumors.

    Aneurysmal bone cysts occur slightly more frequently in females than in males and there is a 20 percent recurrence rate with treatment. However, recurrence of ABCs of the spine is rare.

  • Causes of aneurysmal bone cysts

    The causes of aneurysmal bone cysts are not known. Three theories are being investigated:

    • That ABCs are formed as a result of trauma.
    • That the aneurysmal bone cyst is a secondary reaction to another bony growth elsewhere in the body. Research has revealed a high incidence of accompanying tumors (specifically chondroblastoma and giant cell tumors) in 23-32 percent of patients with an aneurysmal bone cyst.
    • That ABCs occur on their own without any other tumors.
  • Symptoms of aneurysmal bone cysts

    Symptoms of aneurysmal bone cysts can include: 

    • Pain
    • Swelling
    • Stiffness
    • Deformity in the area of the growth
    • The feeling of warmth over the affected area
    • Decreased range of motion, weakness or stiffness
  • Diagnosing aneurysmal bone cysts

    If an aneurysmal bone cyst is not treated it can disrupt growth plates in young patients, cause neurologic symptoms (depending on its location), and fractures.

    At The Children’s Hospital of Philadelphia, our clinical experts use a variety of diagnostic tests to diagnose aneurysmal bone cysts, including:

    • X-rays, which produce images of bones.
    • Magnetic resonance imaging (MRI), which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body.
    • Computed tomography (CT) scan, which uses a combination of X-rays and computer technology to produce cross-sectional images ("slices") of the body.
    • Angiography, a radiograph-type X-ray test which reveals the inside of blood vessels and organs.
    • Radioisotope bone scan, which determines occurrence of any bone metabolic activity. 
    • Biopsy, where a sample of the growth is surgically removed and tested to determine the type of tumor.
    • EOS imaging, an imaging technology that creates 3-dimensional models from two planar images. Unlike a CT scan, EOS images are taken while the child is in an upright or standing position, enabling improved diagnosis due to weight-bearing positioning.
  • Treating aneurysmal bone cysts

    A minority of aneurysmal bone cysts will resolve on their own, but most will need to be surgically removed.

    Though surgery for aneurysmal bone cysts is highly effective, we understand that any surgery can be a stressful experience for children and families. At CHOP, we offer a wealth of resources about how to prepare your child for surgery and what to expect during surgery.

    Additionally, we employ numerous best practices before, during and after surgery to decrease the risk of infection and increase positive outcomes. Safety in spine surgery is a top priority.

    Treatment for aneurysmal bone cysts typically involves a four-step surgical process that includes:

    • Intralesional curettage, which involves scraping out the bone to completely remove the tumor and filling the space with material such as diluted phenol
    • High-speed bur, which involves “shaving” the affected bone to be smooth with a high-speed drill
    • Electrocautery, a surgical technique that uses a high frequency electric current to cut or seal blood vessels
    • Bone grafting, a surgical procedure to replace missing bone with artificial graft material, cadaver bone or bone from another area of the patient

    After surgery for aneurysmal bone cysts, your child should expect to stay overnight in the Hospital.

    In certain conditions, it is recommended to watch the tumor — instead of surgically treating it — and let it resolve on its own. When the growth is in a hard-to-reach place, an intralesional injection is often the best treatment. Your child’s clinical team will recommend the best treatment for your child’s individual situation.

  • Follow-up care for aneurysmal bone cysts

    At The Children's Hospital of Philadelphia, we offer ongoing support and services for patients and families at our Main Campus and throughout our CHOP Care Network. Our team is committed to partnering with parents and referring physicians to provide the most current, comprehensive and specialized care possible for your child.

    Aneurysmal bone cysts tumors can recur in 20 percent of patients, so it is important for your child to continue to see a doctor after treatment.

    Your child will see the orthopedic surgeon about one to two weeks after surgery, then again at three and six months post-surgery. Annual monitoring by trained clinicians is strongly encouraged to monitor for possible recurrence of the growth.

    If continued care and monitoring is necessary, we will help transition your child's care to an adult orthopedic team.

  • Long-term outcomes for aneurysmal bone cysts

    Treatment for aneurysmal bone cysts of the spine usually results in few complications and low recurrence in children.

Reviewed by John P. Dormans, MD, FACS, Jason L. Katz, PA-C, MHS, ATC-R on May 19, 2014