Treatments for Unicameral Bone Cyst in Children

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Treatment for a unicameral bone cyst

Specific treatment for a unicameral bone cyst will be determined by your child's physician based on:

   •   your child's age, overall health, and medical history
   •   extent of the disease
   •   your child's tolerance for specific medications, procedures, or therapies
   •    how your child's physician expects the disease may progress 
   •   your opinion or preference

Treatment is aimed primarily at preventing recurrent fractures. If it is decided that the bone is relatively strong, observation may be recommended. If the child's activities are such that fracture is unlikely (especially in the humerus) observation may be recommended.

The decision to treat is sometimes difficult and the risks of the surgery must be compared to the likelihood of fracture without treatment. There is no right answer for everyone. If treatment is opted for, it will likely involve one or a combination of the following surgical procedures performed by a pediatric orthopaedic surgeon:

Curettage/Bone Grafting

Curettage describes a surgical scraping of the cyst with a special instrument called a curette that has a scoop, loop or ring at its tip. For this procedure, surgeons make an incision in the bone to create a window. The fluid in the cyst is aspirated and the lining tissue is completely curetted. The remaining cavity is then packed with donor bone tissue (allograft), bone chips taken from another bone (autograft), or other materials depending on the preference of the surgeon. 

Steroid Injection

Injection of the steroid methylprednisone acetate into these cysts can help heal the cyst, sometimes without any other therapy. The steroid's healing ability is not fully understood, although it is believed that steroids can reduce the levels of prostaglandin, a type of fatty acid found in the cyst fluid. Prostaglandin is believed to reduce the cyst's ability to reabsorb into the bone.

For this procedure, spinal or bone marrow biopsy needles are placed into the cyst and the fluid is aspirated. The cyst is injected with radiographic contrast, which helps doctors determine whether the cyst can be filled. Then, the steroid is injected and the needles are removed. The cyst will likely be reinjected at regular intervals every several months, until there is adequate healing, which may take 6-12 months. Overall, the results of steroid injection are similar to curettage and the procedure is much easier on the child, so it is usually preferred to curettage as the first treatment. The risks of this treatment are minimal and generally restricted to the risk of general anesthesia, infection, fracture, and recurrence or persistence of the cyst. There is one case report of air getting into the blood stream. This is a potentially dangerous complication, but it is very unlikely to occur.

Bone marrow injection

Some evidence suggests that bone marrow aspirated from the pelvis above the hip through a small needle and injected in the cyst will help the healing. This is sometimes used in conjunction with demineralized bone gel to stimulate bone formation. The demineralized bone is from donor (allograft) bones. The calcium is removed in these preparations, but the bone proteins that stimulate bone formation remain, and it is believed that this may stimulate healing. The preparation is tested for transmissible diseases such as AIDS (HIV), hepatitis and bacteria and is believed to be very safe. Whether or not this approach is better or inferior to simple steroid injection is unknown.

What is the long-term outlook for a child with a unicameral bone cyst?

Prognosis for a unicameral bone cyst is generally good. Most of these cysts do heal with proper treatment and if left alone, most heal spontaneously by the time the skeleton ceases to grow. Recurrence can, however, occur. Continuous follow-up care is essential for the successful treatment of this kind of bone cyst. A schedule of follow-up care should be determined by your child's physician and other members of your care team to monitor ongoing response to treatment and possible late effects of treatment.

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