Bone cyst is a cavity in the bone tissue that occurs due to local circulatory disorders and activation of enzymes that destroy the organic matter of the bone. In the initial stages, it is asymptomatic or accompanied by minor pain. Often, the first sign of a pathological process becomes a pathological fracture. The duration of the disease is about 2 years, during the second year the cyst decreases in size and disappears. The diagnosis is made on the basis of radiography. Treatment is usually conservative: immobilization, punctures, administration of drugs into the cyst cavity, exercise therapy, physiotherapy. In case of inefficiency, resection is performed followed by alloplasty.
Bone cyst is a disease in which a cavity forms in the bone tissue. The causes are unknown. Children and teenagers usually get sick. There are two types of cysts: solitary and aneurysmal, the former are three times more common in boys, the latter are usually detected in girls. By itself, the cyst does not pose a threat to the life and health of the patient, however, it can cause pathological fractures and sometimes causes the development of contracture of a nearby joint. With an aneurysmal cyst in the vertebra, neurological symptoms may appear. Treatment of bone cysts is carried out by orthopedic traumatologists.
The formation of a bone cyst begins with a violation of blood circulation in a limited area of the bone. Due to the lack of oxygen and nutrients, the site begins to break down, which leads to the activation of lysosomal enzymes that break down collagen, glycosaminoglycans and other proteins. A liquid-filled cavity with high hydrostatic and osmotic pressure is formed. This, as well as a large number of enzymes in the fluid inside the cyst, leads to further destruction of the surrounding bone tissue. Subsequently, the fluid pressure decreases, the activity of enzymes decreases, the cyst turns from active to passive and disappears over time, gradually being replaced by new bone tissue.
Solitary bone cyst
Boys 10-15 years old suffer more often. At the same time, earlier development is also possible – a case of solitary cyst in a 2-month-old child is described in the literature. In adults, bone cysts are extremely rare and usually represent a residual cavity after an undiagnosed disease suffered in childhood. As a rule, cavities occur in long tubular bones, the first place in prevalence is occupied by bone cysts of the proximal metaphysis of the femur and humerus.
The course of the disease in the initial stages is asymptomatic in most cases, sometimes patients note slight swelling and minor unstable pain. In children under the age of 10, swelling is sometimes observed, contractures of the adjacent joint may develop. With large cysts in the proximal diaphysis of the thigh, lameness is possible, with damage to the humerus, discomfort and unpleasant sensations with sudden movements and lifting of the arm.
The reason for going to the doctor and the first symptom of a solitary bone cyst is often a pathological fracture that occurs after a minor traumatic impact. Sometimes the injury cannot be detected at all. When examining a patient with the initial stages of the disease, local changes are not pronounced. There is no edema (the exception is edema after a pathological fracture), there is no hyperemia, the venous pattern on the skin is not pronounced, local and general hyperthermia is absent. Minor muscle atrophy may be detected.
When palpating the affected area, in some cases it is possible to detect a painless club-shaped thickening with bone density. If the cyst reaches a significant size, when pressed, the cyst wall may bend. In the absence of a fracture, active and passive movements are in full, the support is preserved. In case of violation of the integrity of the bone, the clinical picture corresponds to a fracture, but the symptoms are less pronounced than in the case of a normal traumatic injury.
Subsequently, a stage course is noted. Initially, the cyst is localized in the metaphysis and connects to the growth zone (osteolysis phase). With large cavities, the bone at the site of the lesion “swells”, repeated pathological fractures may develop. The formation of contracture of the nearby joint is possible. After 8-12 months, the cyst turns from active to passive, loses its connection with the germ zone, gradually decreases in size and begins to shift to the metadiaphysis (the phase of delineation). After 1.5-2 years from the onset of the disease, the cyst turns out to be in the diaphysis and does not manifest clinically in any way (recovery phase). At the same time, due to the presence of a cavity, the strength of the bone at the site of the lesion decreases, therefore, pathological fractures are also possible at this stage. The outcome is either a small residual cavity or a limited area of osteosclerosis. Clinically, there is a complete recovery.
To clarify the diagnosis, an X-ray examination of the affected segment is performed: femur x-ray, humerus x-ray, etc. Based on the X-ray picture, the phase of the pathological process is determined. In the phase of osteolysis, the image shows a structureless rarefaction of the metaphysis in contact with the growth zone. In the phase of delineation, radiographs show a cavity with a cellular pattern, surrounded by a dense wall and separated from the growth zone by a section of normal bone. In the recovery phase, an area of bone compaction or a small residual cavity is revealed in the images.
Aneurysmal bone cyst
It is less common than solitary. Usually occurs in girls 10-15 years old. It can affect the pelvic bones and vertebrae, metaphyses of long tubular bones are less likely to suffer. Unlike a solitary bone cyst, it usually occurs after an injury. The formation of the cavity is accompanied by intense pain and progressive swelling of the affected area. Examination reveals local hyperthermia and dilation of subcutaneous veins. When localized in the bones of the lower extremities, there is a violation of the support. The disease is often accompanied by the development of contracture of the nearby joint. With bone cysts in the vertebrae, neurological disorders appear due to compression of the spinal roots.
There are two forms of aneurysmal bone cysts: central and eccentric. During the course of the disease, the same phases are distinguished as with solitary cysts. Clinical manifestations reach a maximum in the phase of osteolysis, gradually decrease in the phase of delineation and disappear in the recovery phase. Radiographs in the phase of osteolysis reveal a structureless focus with an extraosseous and intraosseous component, with eccentric cysts, the extraosseous part is larger than the intraosseous one. The periosteum is always preserved. In the phase of delineation between the intraosseous zone and healthy bone, a sclerosis site is formed, and the extraosseous zone is compacted and reduced in size. In the recovery phase, an area of hyperostosis or a residual cavity is detected on radiographs.
Treatment is carried out by pediatric orthopedists, in small settlements – traumatologists or pediatric surgeons. Even if there is no fracture, it is recommended to unload the limb using crutches (with a lesion of the lower limb) or hanging the arm on a kerchief bandage (with a lesion of the upper limb). In case of a pathological fracture, a plaster is applied for a period of 6 weeks. In order to accelerate the maturation of the tumor-like formation, punctures are performed.
The contents of the cyst are removed using special needles for intraosseous anesthesia. Then multiple perforation of the walls is carried out to reduce the pressure inside the cyst. The cavity is washed with distilled water or saline solution to remove cleavage products and enzymes. Then washing is performed with a 5% solution of e-aminocaproic acid to neutralize fibrinolysis. At the final stage, aprotinin is injected into the cavity. With a large cyst in patients older than 12 years, the administration of triamcinolone or hydrocortisone is possible. With active cysts, the procedure is repeated 1 time in 3 weeks, with closed cysts – 1 time in 4-5 weeks. Usually 6-10 punctures are required.
During treatment, X-ray monitoring is carried out regularly. If there are signs of a decrease in the patient’s cavity, they are directed to physical therapy. With the ineffectiveness of conservative therapy, the threat of compression of the spinal cord or the risk of significant bone destruction, surgical treatment is indicated – marginal resection of the affected area and alloplasty of the resulting defect. In the active phase, when the cyst is connected to the growth zone, operations are performed only in extreme cases, since the risk of damaging the growth zone increases, which is fraught with lagging limb growth in the long term. In addition, when the cavity comes into contact with the germ zone, the risk of relapses increases.
Prognosis and prevention
The prognosis is usually favorable. After the reduction of the cavity, recovery occurs, the ability to work is not limited. The long-term consequences of cysts may be due to the formation of contractures and massive destruction of bone tissue with shortening and deformity of the limb, however, with timely adequate treatment and compliance with the doctor’s recommendations, such an outcome is rarely observed.
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