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?

Unicameral bone cysts are non-cancerous bone tumors that mostly occur in children and teens, especially in boys. The exact cause is unknown, but one theory is that poor blood flow in the bone leads to bone loss, creating a fluid-filled cavity.

What Are Signs & Symptoms of Unicameral Bone Cysts?

Most children with a unicameral bone cyst have no symptoms. These cysts are often found by accident during imaging for another issue or after a bone breaks in the area weakened by the cyst. In some cases, pain may be the first sign.

Every child is different, and symptoms can vary. The signs of a unicameral bone cyst can look like other health problems. Always talk to your child’s doctor if they have new pain or a decrease in movement.

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.

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 UBCs depends on several factors, including the size and location of the cyst, how strong the bone is, and the risk of a fracture.

Treatment Options

Watchful Waiting (Nonoperative Care)

Small cysts that aren’t causing symptoms can often just be watched over time. Your doctor may order follow-up X-rays to monitor the cyst’s size. In some cases, your child may need to limit physical activity—especially sports—if there's a risk of breaking the bone. If a fracture does happen (often in the arm), your doctor may wait to see if the fracture and cyst heal on their own. Sometimes, the cyst goes away after the bone heals.

Sclerograft Procedure (Sclerosis and Grafting)

This is a newer, minimally invasive procedure developed by Lurie Children's Interventional Radiology team. While your child is asleep, two small needles are placed into the cyst to drain the fluid. A chemical called a sclerosant is injected to destroy the cyst, and a special bone graft is added to help strengthen the area. The graft is temporary and fades as healthy bone grows in over a few months. This technique has low recurrence rates and does not require stitches, making it a preferred approach.

Surgery

Surgery may be needed if the cyst is in a critical area or if the bone has broken and isn’t stable. During surgery, the cyst lining is scraped out (called curettage), and the space is filled with bone graft to help the bone heal.

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.

Because of our extensive experience treating UBCs, Lurie Children’s has become a destination for patients from across North America and around the world seeking minimally invasive care.

Meet one of our patients in the video below:

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 are unlikely to recur after your child has reached skeletal maturity, generally around the age of 18.