Many bone cysts heal without treatment. However, treatment is sometimes necessary if the cyst is painful or to prevent the bone fracturing.
Unicameral bone cyst
If the cyst is small and the affected bone is strong, a policy of watchful waiting may be recommended. This means your child will not receive any immediate treatment, but they will be given regular check-ups to make sure the cyst is not getting larger. About one in four unicameral bone cysts heal by themselves without the need for treatment.
Surgical treatment may be recommended if the cyst does not show any signs of healing or if the bone is thought to have a high risk of fracture. There are three main types of surgical treatment:
- steroid injection
- bone marrow injection
- curettage and bone grafting
All three techniques are carried out under general anaesthetic, which means that your child will be asleep during the surgery and will not feel any pain.
In some cases, a combination of two or all three techniques may be used. Each technique is discussed in more detail below.
A type of steroid called methylprednisolone acetate is the preferred steroid for this type of treatment. It is thought that methylprednisolone acetate encourages the stimulation of a chemical called prostaglandin, which helps prevent the cyst growing.
The surgeon will drain the fluid out of the cyst before injecting the steroids into it. Repeated injections may be required every few months over the course of a year before the cyst fully heals.
As steroid injection is a relatively straightforward type of treatment, it is often the first treatment to be used. Additional treatment options will only be used if the cyst shows no sign of healing.
Bone marrow injection
Bone marrow injection is similar to a steroid injection. The surgeon injects the cyst with bone marrow that has been removed from another part of your child's body, usually their pelvis.
Bone marrow contains specialised cells which should encourage the cyst to heal. In most cases, a single injection of bone marrow is required.
Curettage and bone grafting
During this procedure a surgeon cuts into the bone to gain access to the cyst.
The fluid inside the cyst is drained and the lining of the cyst scraped out using a tool called a curette. The resulting cavity inside the bone is filled with chips of bone, either from other parts of your child's body or from donated bone tissue.
In around 10-20% of cases, bone cysts may recur during the first two years after treatment, especially with larger cysts or in young people. Therefore, it is likely your child will have regular X-rays to assess the condition of the previously affected bone.
It is impossible to predict the recurrence rates of bone cysts that do not cause any symptoms because most go undiagnosed.
Aneurysmal bone cyst
Aneurysmal bone cysts are typically treated using curettage and bone grafting, as described above.
In some cases, additional treatments such as liquid nitrogen (a very cold substance) may be used to damage the tissue of the cyst.
Some aneurysmal bone cysts will heal spontaneously following a simple biopsy. About one in five aneurysmal bone cysts will recur following treatment, almost always within the first 18 months.