What are the types of bone cysts?
A solitary, or simple, cyst is a single-chamber cavity with clear liquid, most often in the upper part of the humerus in children 5–15 years old. It grows slowly and may close on its own over time. An aneurysmal cyst consists of many cavities filled with blood, grows faster, swells the bone more, and more often causes pain and swelling. Both are benign formations, but the aneurysmal one requires more active tactics. Separately, cysts that have arisen along with other bone changes are isolated, so the doctor always evaluates the entire image.
- Solitary (simple) bone cyst - one cavity with fluid
- Aneurysmal bone cyst - multi-chambered, with blood
- Active cyst located next to the growth zone
- Inactive cyst that moves away from the growth plate with age
- Secondary cysts against the background of other bone changes
Reasons
The exact cause of a simple bone cyst is unknown. The main hypothesis associates it with a violation of the venous outflow inside the bone in the active growth zone: the fluid pressure increases and gradually dissolves the bone tissue from the inside. An aneurysmal cyst today is considered as a process with certain genetic rearrangements; sometimes it develops against the background of another bone formation. Cysts are not associated with diet, lack of calcium, bruises or sports, although it is often injury that brings them to attention, causing a fracture.
- Disturbance of venous outflow in growing bone
- Genetic rearrangements in aneurysmal cysts
- Development against the background of another bone formation
- Active skeletal growth in childhood and adolescence
- Not associated with calcium deficiency or exercise
Symptoms
Most simple cysts are asymptomatic and are discovered by chance during an X-ray for another reason. Sometimes there is a mild pain during exercise or a feeling of discomfort in the bone. With an aneurysmal cyst, there is often constant aching pain, swelling and limitation of movement in the adjacent joint. The key event is a pathological fracture: the bone breaks during normal movement, throwing a ball, or falling from a small height. Such a fracture causes severe pain and deformation and requires immediate assistance.
- Most often asymptomatic
- Dull pain in the bone with exertion
- Swelling over the bone with an aneurysmal cyst
- Limitation of movement in an adjacent joint
- Pathological fracture due to minor trauma
- Lameness due to damage to the femur
Diagnostics
The main method is x-ray of the bone in two projections: the cyst looks like a clearly defined clearing area with a thinned cortical layer. Usually this is enough for a preliminary diagnosis. CT clarifies the thickness of the walls and helps assess the risk of fracture, MRI shows the contents of the cavity and the soft tissue around it, and with an aneurysmal cyst, characteristic fluid levels are visible. If the presentation is atypical, such as rest pain, cortical destruction, or a soft tissue component, a biopsy is performed to rule out tumor. Blood tests are needed to assess your general condition and rule out other bone diseases.
- X-ray of bone in two projections
- CT scan to assess the walls and fracture risk
- MRI for content and soft tissue assessment
- Biopsy for an atypical picture
- Blood calcium, phosphorus and alkaline phosphatase
- Control shots in dynamics
Treatment
Tactics are chosen individually. Small asymptomatic cysts far from the growth zone and with a thick wall are often simply observed, limiting traumatic sports: many of them close after the end of skeletal growth. If there is a high risk of fracture or a fracture has already occurred, puncture of the cavity is used with the introduction of drugs or a bone substitute, curettage with filling with a bone graft, as well as the installation of elastic rods inside the bone, which simultaneously strengthen it and improve the outflow of fluid. Relapses are possible, so after treatment follow-up images are needed for several years.
- Observation with limited contact sports
- Puncture of the cyst with administration of drugs
- Curettage with bone grafting
- Intramedullary elastic osteosynthesis
- Treatment of pathological fracture
- Control radiographs before the end of growth