Site of predilection: The size of the osteoid osteoma is another characteristic of this lesion, which has been limited to 1 cm, but has also been reported to be 1.5 cm, and in general is not large in size. The preferred sites are mostly long tubular bones, especially in the lower extremities. Nearly 50% to 60% of the cases occurred in the femur and tibia. In a group of 661 cases of osteoid osteoma, the most frequent site was the femur, followed by the tibia. Both cases accounted for 57% of the total number of cases. In the hand, osteoid osteoma was often located in the proximal phalanges and metacarpals, while in the distal phalanges it was found in 71% of the total.
The distal phalanges are rare. The incidence of osteoid osteoma is high in the navicular bones of the wrist, and in the foot, it is mostly located in the talus and heel bone. In long tubular bones, osteoid osteoma is located in the diaphysis. Osteoma of the epiphysis and intra-articular bone is rare. In the proximal femur, they are often located in the neck and intertrochanteric region.
Osteoid osteoma of the spine often occurs in posterior spinal structures, such as the base of the transverse process, the vertebral plates, the pedicle, and vertebral body invasion is rare. In order of incidence, the lumbar, cervical, and thoracic vertebrae. Sacral spine is rare.
Osteoid osteoma occurs between the ages of 7 and 25. Pain is the main symptom. If there is no pain, the diagnosis is doubtful. The pain is characterized by nocturnal intensity and is relieved when a small amount of salicylic acid is administered. The nature of the pain is often dull or stabbing. It is mild and intermittent at first, so sometimes it is months to years before the patient comes to the clinic. Later the pain worsens and becomes persistent. It may also be accompanied by local soft tissue swelling or tenderness. The mechanism of the pain is not clear.
It is thought that the prostaglandin products produced within the tumor tissue can cause changes in vascular pressure and stimulate local nerve endings. This view is supported by the presence of unmyelinated nerve fibers found within the peripheral fibrous zone of the lesion core or in the core itself. Other clinical manifestations of osteoid osteoma can be related to the age of the patient at onset, and the site of the invaded bone. In immature bone, muscle atrophy and skeletal deformities may be present. If the osteoid osteoma is located in the spinal column, it may present with a sloping neck, spinal stiffness, and scoliosis. In the case of osteoid osteoma located in the joint, localized pressure pain, swelling of synovial membrane, and limitation of movement may occur. Osteoid osteoma can have various clinical manifestations, but laboratory tests are generally normal.
X-rays: The typical x-ray presentation is an oval or circular central x-ray transparency <1 cm in diameter, surrounded by a uniform sclerotic zone. In practice, this is not entirely typical, as osteoid osteoma of the spine, carpal bones, and foot bones may appear differently than osteoid osteoma on long tubular bones. The lesions can occur in the bone stem, in the medullary cavity or in the osteophytes, or in the subperiosteum, resulting in different x-ray signs.
1.Long tubular bone: Osteoid osteoma located in long tubular bone often occurs on the bone stem, and there is a radiolucent shadow in the bone cortex, which is called a nest, and there can be different degrees of calcification foci in the nest. The nest is surrounded by sclerotic bone and is accompanied by thickening of the bone cortex. This is due to subperiosteal and endosteal new bone formation. In rare cases, there can be several osteoid osteomas in the same bone, each with its own nest.
The presence and morphology of the nests should be determined by further examination with the aid of x-ray tomography or CT. Osteoid osteoma in the femoral neck often occurs on the medial aspect of the femoral neck, with the nests located subperiosteal or within the bone cortex. Under normal circumstances, the medial cortex of the femoral neck is thicker, thus making the diagnosis difficult if there is mild cortical thickening. In addition, in areas with thickened bone cortex and translucent areas, care should be taken to differentiate from stress fractures.
2. Carpal, tarsal and epiphysis: Osteoid osteoma in the carpal and tarsal bones and the epiphysis of long tubular bones often occurs in osteophytes, and the X-ray shows a round lesion with partial or complete calcification. The lack of peripheral reactive osteosclerosis makes this presentation completely different from that of supracortical osteoid osteoma, making it more difficult to diagnose. In children with immature bones, osteoid osteoma in the epiphysis can cause deformities in bone development.
3. Small bones of the hands and feet: osteoid osteoma in the metacarpals, metatarsals, and phalanges, if located in the bone cortex, has the same performance as that seen in long tubular bones. If it is located under the periosteum, “scallop”-like changes can be seen in the surrounding bone cortex. In the small bones of the hands and feet, osteoid osteoma is often accompanied by soft tissue swelling.
4.Intra-articular: If osteoid osteoma occurs in the joint, it can cause pain, soft tissue swelling, joint effusion and limited joint movement. It is often misdiagnosed as a joint disorder. Special attention should be paid during the examination.
5.Spine: Due to the complex anatomy of the spine, the bone is often obscured by the surrounding soft tissues on ordinary X-rays, and the clinical manifestations can have different symptoms, thus making the diagnosis of osteoid osteoma in the spine very difficult. The clinical manifestations are often severe radiating pain, which is aggravated at night or when moving the spine. Most patients have scoliosis, which is called painful scoliosis. Therefore, in cases of scoliosis with significant pain, it is often considered an important clinical manifestation of supraspinal osteoid osteoma.
This symptom is, of course, not unique to osteoid osteoma of the spine. Osteoid osteoma of the cervical spine may present with a sloping neck. Neurologic symptoms are rare in supraspinal osteoid osteoma.
Supraspinal osteoid osteoma is characteristically located on the concave side of the scoliotic spine, near the apex of the scoliosis. It may be seen in the vertebral arch, lamina, articular eminence, and occasionally a sclerotic area on the transverse process. The detection of radiolucent nests on plain radiographs is very difficult and requires the help of tomography or CT. It should be emphasized that a sclerotic bone lesion found on the posterior structures of the spine is an important sign for the diagnosis of osteoid osteoma, but metastatic carcinoma of bone, infection, and spondylitis can also have this presentation, and attention should be paid to the differential diagnosis.
Frontal and lateral radiographs of the femur showed a round translucent area in the medial cortex of the left femoral stem with sclerosis of the surrounding bone.
Nuclear scan and gamma scintigraphy: Preoperative nuclear scan and gamma scintigraphy in patients with osteoid osteoma should be done as a routine examination. For osteoid osteoma of the spine, the X-ray diagnosis is inaccurate, while the nuclear scan is sensitive and reliable for the examination of the lesion. The application of nuclide scanning can result in a double density sign in osteoid osteoma: increased scintillation activity in the nests of osteoid osteoma and less radionuclide clustering in the surrounding sclerotic areas. This sign is helpful for the diagnosis of osteoid osteoma.
1. Gross examination In the complete specimen, the tumor is clearly demarcated from the surrounding bone tissue, round or oval in shape, small in size, usually about 1 cm in diameter, rarely more than 2 cm. the surrounding tissue undergoes reactive sclerosis and the tumor is located in its center. The color and firmness of the tumor varies with its constituent components. When bone-like tissue predominates, the core is brownish red, interspersed with yellow or white spots, granular or gravelly in texture, and a transparent area on X-ray. When the core is composed of dense bone trabeculae, it is reddish-white with hard and dense texture, and the X-ray is a dense area. The tumor is separated from the surrounding bone tissue by a narrow, ring-like congested band. The surrounding bone tissues generally have reactive osteosclerosis, especially if the tumor occurs in the bone cortex, which is most obvious.
2.Microscopic examination The nest of osteoid osteoma may have bone in different stages of maturation and rich vascular connective tissue stroma with different proportions of osteoid tissue and new bone trabeculae. While the core is dense and firm in appearance on visual examination, microscopically it appears as closely spaced atypical new bone trabeculae with enlarged blood sinuses between the trabeculae. The newly formed trabeculae are each overlaid with osteoblasts and often have a few osteoclasts.
It is worth noting that osteoid osteoma is very similar to osteoblastoma in histological examination, and the differential diagnosis should be made with reference to the size, location and clinical manifestations of the tumor.
Overview of treatment]
The principle of surgical treatment is accurate localization and complete excision, including the nest of osteoid osteoma and the surrounding reactive sclerotic bone. If the osteoid osteoma is not completely excised during surgery and the nest is not found during postoperative pathological examination, the clinical symptoms can disappear in this case, but it is easy to recur after surgery.
For accurate localization of osteoid osteoma during surgery and complete excision, a radionuclear technique can be used. A radionuclide can be administered to the patient 2h before surgery and a sterilized radionuclide probe can be used intraoperatively to detect the active area of the radionuclide. The specimen is placed at the probe after excision to confirm that it is the highest peak radionuclide and that the surrounding bone radionuclide reaches normal levels after excision. This ensures that the surgical excision is complete.
Osteoid osteoma is a benign tumor, and there have been no reports of malignancy or metastasis of osteoid osteoma.