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Bone Cysts

Bone cysts are pockets of fluid in the bones that are common in children and teens as they grow.

Many bone cysts don't cause symptoms and don't require treatment. But some require surgery because they can weaken the bones and affect your child's growth.

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What Is a Bone Cyst?

Bone cysts are abnormal, liquid-filled pockets that form within the bones. They happen most often in childhood and during the teenage years.

Bone cysts most often develop in long bones — the bones in the arms or legs. They often occur near growth plates, which are near the ends of bones, at the joints.

Bone cysts aren't cancerous, and they won't spread to other parts of your body. But bone cysts can:

  • Cause pain and swelling.
  • Interfere with a child's growth.
  • Press on nerves, affecting feeling or movement.

For these reasons, some bone cysts require treatment.

How common are bone cysts?

Many bone cysts don't cause symptoms and go away on their own over time. Because bone cysts often go undetected, doctors don't know how common they are.

What are the types of bone cysts?

There are two main types of bone cysts:

  • Unicameral bone cysts. A unicameral — or simple — cyst is the most common type of bone cyst. These fluid-filled cysts are benign (not cancerous) and won't spread to other parts of the body.
  • Aneurysmal bone cysts. Although they're also benign, aneurysmal bone cysts can be more serious. They have many sacs filled with blood and other fluids and are more likely to cause symptoms and affect bone growth.

What causes bone cysts?

In most cases, doctors don't know why bone cysts happen. As they often occur in children and adolescents, bone cysts seem to happen as the bone grows.

A solid tumor in the bone causes about 30% of aneurysmal bone cysts to form. That tumor is usually also benign.

What are bone cyst risk factors and complications?

Bone cyst risk factors

Children and teenagers are much more likely to get bone cysts than adults. More than 80% of bone cysts occur between the ages of 10 and 20, according to the National Library of Medicine.

A unicameral bone cyst, the most common type, is twice as likely in males than in females. Aneurysmal bone cysts are slightly more common in girls and women.

Complications of bone cysts

If not treated, some bone cysts can cause serious health problems. These include:

  • A break, or fracture, in the bone.
  • A deformity in the bone.
  • Nerve damage.
  • One arm or leg that is shorter than the other.

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What Are the Signs and Symptoms of Bone Cysts?

Because bone cysts often don't cause symptoms, many people don't know they have a bone cyst.

You might only find out your child has a bone cyst after an injury or overuse causes the bone to break. When they get an x-ray, the cyst shows up. Doctors might also find bone cysts when they do an x-ray for a reason unrelated to a broken bone.

Symptoms you might notice include:

  • A slight bump.
  • Pain.
  • Stiffness in a joint.
  • Swelling.
  • Tingling, numbness, muscle weakness, or difficulty using the bathroom. (These symptoms can happen with bone cysts in the spine).

If your child has bone cyst symptoms, talk to your doctor. They can do an x-ray and find out if it's a bone cyst or another health problem.

Bone cysts are most commonly found in the arm or leg bones, and then the spine. However, cysts can occur in any bone in the body.

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How Do You Diagnose a Bone Cyst?

Doctors can't tell if your child has a bone cyst through a physical exam. They need to order imaging tests.

Tests to diagnose a bone cyst

A bone cyst may show up on these imaging tests:

If your doctor sees a bone cyst on an x-ray, they may order an MRI or CT scan to identify the kind of bone cyst. They may also order a bone biopsy to rule out other problems, like a tumor.

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How Do You Treat a Bone Cyst?

Many benign cysts will heal on their own over time. Your doctor may want to monitor your child's cyst over time with x-rays to see if it will need treatment.

If a bone cyst needs treatment, the treatment option will depend on how severe the cyst is and where it is in the body. Your doctor will explain the benefits and risks of the treatment options.

Bone cysts can return after treatment. Your doctor may suggest routine x-rays to watch for signs of reoccurrence.

Drainage of bone cysts

Doctors can drain some cysts by using a needle to remove the fluid. Then, they fill the area with medicine, usually a steroid, to help with healing. The surgeon will use CT scanning or another technology to precisely locate the cyst.

In most cases, a doctor will give medicine so your child will be asleep during the procedure and not feel anything. Sometimes, doctors use local anesthesia, so they're awake but don't feel pain.

Surgery to remove bone cysts

Larger cysts and cysts that cause a break in the bone may require surgery. The surgeon will drain the cyst and scrape out the cyst tissue.

The doctor will then repair the broken bone with a bone graft or cement mixture to make the bone stronger. Doctors make a bone graft from an unnecessary piece of bone removed from elsewhere in the body. In some cases, a bone graft comes from a donor.

Rarely, doctors will need to remove part of the bone, beyond the cyst. The surgeon may suggest this if a cyst has caused major damage to the bone or keeps coming back. This type of surgery is usually only possible if the cyst occurs in a less important bone.

Radiation therapy for bone cysts

A doctor may suggest radiation therapy for aneurysmal bone cysts in areas of the spine or pelvis that are harder to access. In these cases, radiation therapy may be safer than surgery, which could damage nearby nerves, veins, or tissue.

Doctors may also suggest radiation therapy for cysts that keep coming back. The goal of this therapy is to kill the cyst cells with minimal damage to nearby bone or other tissue.

Sclerotherapy or arterial embolization for bone cysts

For this therapy, doctors inject medications that cut off blood supply to the veins in or around the cyst. Doctors may choose this therapy for some aneurysmal bone cysts.

How effective is bone cyst treatment?

Treatment resolves a bone cyst in most cases.

But people who've had a bone cyst are at risk of getting another one. This is especially true for aneurysmal bone cysts.

Doctors may suggest routine follow-up for those who had an aneurysmal bone cyst, more than one cyst, or a large cyst. This may involve x-rays and physical exams to watch for new bone cysts.

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