Unicameral Bone Cysts

What Are Unicameral Bone Cysts?

A unicameral bone cyst (UBC), also known as a simple bone cyst, is a fluid-filled cavity in the bone. It usually occurs in the long bones of a growing child, especially the upper part of the arm (humerus) or the upper part of the leg (femur); however, other bones can also be affected.

UBCs are considered benign and do not spread beyond the bone. The cysts weaken the bone and can cause pain, fracture and growth disturbances.

UBCs may heal spontaneously by the time the child reaches skeletal maturity; however, others may not heal and will continue to grow.

What Causes Unicameral Bone Cysts?

The cause of a unicameral bone cyst remains unknown. There are many different theories; however, none has been definitively proven.

What Are Signs & Symptoms of Unicameral Bone Cysts?

Most children with a unicameral bone cyst are generally asymptomatic (without symptoms). In most cases, unicameral bone cysts are only discovered when the child breaks the bone that has been weakened by the bone cyst or, incidentally, during imaging obtained for other reasons. There may be an abnormal angulation of the limb secondary to the fracture or shortening of the limb if the adjacent growth plate is involved.

It is important to note that each child experiences symptoms differently. The symptoms of a unicameral bone cyst may resemble other conditions or medical problems. Always consult your child's physician for a diagnosis.

How Are Unicameral Bone Cysts Diagnosed?

At Lurie Children’s, your child's diagnostic evaluation begins with a thorough medical history and physical examination of your child. Our clinical staff may use a variety of diagnostic tests to diagnose unicameral bone cysts, including:

  • X-rays, which produce images of bones on film. 
  • Magnetic resonance imaging (MRI), which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs, soft tissues, muscles, ligaments and other structures within the body. Your child is exposed to no radiation during an MRI.
  • Needle biopsy, a procedure where a doctor places a small needle through the skin and into the lesion to withdraw a sample of the abnormal tissue. The tissue is analyzed to confirm any findings.

In addition to diagnosing the specific type of lesion your child may have, these tests will also help determine the size and location of the cyst. All of this information is crucial in determining the best treatment options for your child.

How Are Unicameral Bone Cysts Treated?

Treatment for unicameral bone cysts depends on a number of factors including where the cyst is located, how strong the bone is, where the cyst is located, and what the chances are for a fracture.

Treatment options include:

  • Nonoperative/”Watchful Waiting”: Small UBCs that are not causing symptoms can be treated by observation and repeating X-rays to watch the size of the UBC. Sometimes your doctor may ask your child to decrease physical activity (including sports) if there is a concern that a fracture could occur through the cyst. Many times, especially a fracture that occurs in the arm, your doctor may recommend waiting for the fracture to heal on its own before recommending surgery. Sometimes, the UBC will even go away on its own after the fracture heals.
  • Sclerosis and Grafting: This is a new minimally-invasive technique which was developed by our Interventional Radiology team. It involves treating the cysts with small needles without the need for stitches. While your child is asleep, two small needles are placed in the cyst to drain the fluid. Next, a sclerosant (a caustic chemical) is injected into the cyst to destroy the underlying cyst. The cyst is then filled with regenerative bone graft to help strengthen the cyst. The bone graft is temporary and usually disappears in a few months once new healthy bone starts forming. The early studies from this technique are very promising and because it is minimally invasive, it is generally the preferred approach.
  • Surgery: Surgery may occasionally be performed in the cases of very large cysts in critical locations or cysts that have fractured and are unstable. If surgery is performed, it may require curettage, which involves scraping the lining of the cyst out of the bone with special tools. Your surgeon may then fill the hole in the bone with bone graft.

Treatment at Lurie Children's

UBCs are treated by our Interventional Radiology team which is made up of doctors, advanced practice providers, nurses and technologists, all sub-specialized in pediatric interventional radiology.

Learn More About Our Team

What Are the Long-Term Effects of Unicameral Bone Cysts?

Unicameral bone cyst tumors can recur— even after treatment — so it is important for your child to continue to see a doctor after treatment. Your child will see their physician about one month after their procedure, and then every three months for at least two years to monitor for possible recurrence.

During follow-up visits, X-rays are recommended to closely monitor the healing bone cyst and make sure there is no recurrence. If the unicameral bone cyst returns, the above procedures can be repeated.

In most cases, unicameral bone cysts will not recur after your child has reached skeletal maturity.

Make an Appointment

To make an appointment with one of our Interventional Radiology specialists, call 312.227.5110 or email IR@luriechildrens.org.

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