Bone and Soft Tissue Tumors

Simple Bone Cyst (Solitary Bone Cyst, Unicameral Bone Cyst)

SIMPLE BONE CYST 

Simple bone cyst is a fluid filled lesion seen within the bone. Simple bone cyst is not a malignant tumor and it shows a benign course. It is seen commonly in proximal humerus and femur. Active bone cysts are adjacent to growth plate. As the child grows the cysts becomes more distal to the growth plate. Simple bone cyst can rarely be seen in other bones. Usually it is located  in only one bone.

What ages is the bone cyst diagnosed?

Simple bone cyst is the most commonly  diagnosed benign tumor of the bone. It is generally seen between 5-15 year old . Bone cysts are not common in adults. Male/female ratio is 2/1.

What causes the simple bone cyst?

Even it is not proven, there are a few theories: The disorders of growth plate and intraosseous venous occlusion theories are two of them.

What are symptoms of bone cysts?

Many bone cysts stay silent and do not cause any symtoms. They are usually diagnosed incidentally Bone cyst may cause thinning of the bone cortex and in circumstances of weight bearing like standing, walking, patient feel pain in the cyst area. Also, with thinning of the bone cortex, the risk of pathological fracture is increased. In the case of fracture, pain, swelling and functional disability are seen.

How is the diagnosis of the bone cyst made?

The diagnosis is generally made with direct x-rays. Bone cyst complicated with fracture can be confirmed by radiological examination. If the bone cyst got complicated with the previous treatments and/or fracture or its unusally location, orthopaedic surgeon might request extra studies like MR, Computed Tomography or bone scan.

What is the treatment for simple bone cyst?

While the small cysts are only followed, the large cysts which might have the pathological fracture risk requires treatment. The cyst is punctured with a special needle and cyst fluid is drawn and inspected. It should be clear and yellowish fluid. A little radio-opaque fluid is injected into the cyst to make sure that it is unicameral and the needle is in the cyst. Then, depending on the orthopedic surgeon’s choice either bone marrow obtained from the patient himself or steroid is injected into the cyst.

The larger bone cysts with the risk of pathological fracture os the cyst not responding injection treatment may require surgical treatment. Surgical treatment consists of curettage and grafting and/or internal fixation. When a simple cyst causes pathological fracture, an intra medullary fixation may be included to the surgical treatment.

Key words: simple bone cyst, solitary bone cyst, unicameral bone cyst, orthopedic surgeon, curettage and grafting, steroid injection, pathological fracture.

About the author

Prof.Dr. Seref Aktas