bubble_chart Overview

In 1935, Jaffe first reported osteoid osteoma, a benign osteogenic disorder characterized by well-defined focal lesions, typically less than 1 cm in diameter, often surrounded by a larger reactive bone area.

bubble_chart Etiology

Not entirely certain, but Jaffe believes it is a primary benign tumor based on the following: ① slow growth; ② normal tissue replaced by osteoid tissue; ③ surrounding bone tissue invariably shows uniformly structured sclerosis; ④ fixed size. These arguments are widely recognized. Other scholars suggest it may be inflammatory, possibly related to viral infection, while others propose a vascular origin or association with arteriovenous developmental abnormalities, or a compensatory process.

bubble_chart Pathological Changes

Gross examination: The lesion may be entirely within the cortex, on the medial aspect of the cortex, between the cortex and the bone membrane, or within the cancellous bone. Lesions in long bones are mostly within the cortex, while those in short bones are often in the cancellous bone, and spinal lesions are usually located in the vertebral arch or articular processes. The tumor always appears oval or round, with a clearly sclerotic boundary from the surrounding bone. Most are granulomatous, with a sandy density, homogeneous, and brownish-red.

Histological examination: Composed of a mixture of bone tissue, osteoid tissue, and new bone, with abundant vascular supporting tissue. The early stage is characterized by a predominance of osteoblasts, which are hyperplastic and densely arranged in a highly vascularized matrix. The intermediate stage [second stage] shows osteoid tissue deposition between osteoblasts, with varying degrees of calcification. The mature stage is characterized by the formation of dense, atypical trabeculae, which are neither lamellar nor woven.

bubble_chart Clinical Manifestations

It is most common in individuals aged 10 to 30, but can also occur in infants under 1 year old or elderly over 60 years of age. Males are more frequently affected than females, with an incidence ratio of 2:1. The incidence in the lower limbs is about three times that of the upper limbs, while occurrences in the trunk bones are relatively rare. The tibia and femur are the most commonly affected, accounting for approximately half of the cases, followed by the fibula, humerus, and spine, among others.

The course of the disease is characteristic, with pain appearing early, often months before abnormalities are visible on X-rays. Initially, the pain is intermittent, worsening at night, and can be alleviated with painkillers. In the late stage [third stage], the pain intensifies, becoming persistent and unresponsive to any medication. The pain is usually localized, and soft tissue swelling may occur, though the affected area is often limited. Some patients may not experience pain at all. When the lesion is small, the pain may be accompanied by vasomotor reactions such as increased skin temperature and profuse sweating. The pain is not necessarily confined to the affected area and may radiate to nearby joints.

X-ray Examination: The disease is most commonly found in the femoral neck and the upper end of the tibia but can involve any bone. The typical X-ray presentation shows a small lesion surrounded by dense bone, most with a diameter of less than 1 cm, featuring a central radiolucent area of lower density that may exhibit varying degrees of calcification. A minority of cases may have more than one lesion, though many lesions may differ from the above description, with no evidence linking them to the site of onset or disease stage. Differentiation from chronic bone abscesses, acute or chronic osteomyelitis, solitary enchondroma, aseptic necrosis, and osteochondritis can be achieved through stirred pulse imaging. Although osteomyelitis may present with congestion, the vascular morphology remains normal or slightly dilated, without the halo phenomenon seen in bone tumors. The necrotic centers of bone abscesses and aseptic necrosis appear as avascular areas.

(1) Cortical Bone Tumor: Features a small radiolucent area surrounded by dense bone, with the lesion located within the cortex and a more pronounced sclerotic ring. The bone membrane reaction may be either layered or homogeneous. In the late stage [third stage] of the disease, the lesion may become completely obscured.

(2) Cancellous Bone Tumor: Most commonly found in the femoral neck, followed by the small bones of the hands and feet and vertebral bodies. The lesion is often surrounded by minimal new bone formation but is encircled by a dense bone ring. Occasionally, reactive new bone formation may occur at distant sites.

(3) Subperiosteal Bone Tumor: Typically presents as a soft tissue mass near the bone, most commonly on the inner aspect of the femoral neck and in the hands and feet. The bone directly beneath the lesion may show a scalloped area due to pressure atrophy or bone resorption. When the lesion is close to a joint, there is no reactive bone formation, but joint swelling, congestion, and pain may occur, resembling acute synovitis. Apart from significant decalcification, no other changes are observed in the bones at both ends of the joint. There is evidence suggesting that the disease may resolve spontaneously, though this requires a prolonged period.

bubble_chart Diagnosis

The diagnosis can be established through clinical manifestations, histological, and radiological examinations. In some cases, prolonged pain may occur before characteristic X-ray findings appear, making the diagnosis more difficult. If unexplained persistent pain is present in young adults or children, the diagnosis of this disease should be considered.

bubble_chart Treatment Measures

The ideal treatment is en bloc resection, which includes the affected bone with the lesion. Complete removal of the lesion leads to rapid symptom resolution. Curettage is generally not recommended, as radiation and chemotherapy are considered ineffective. Locating the exact site during surgery can be challenging, but intraoperative X-ray-guided drilling aids in localization. Postoperative X-ray review is also necessary. Recurrence is rare after complete lesion removal, whereas incomplete curettage often results in recurrence, with varying time intervals. In some cases, the lesion cannot be identified during surgery. Interestingly, half of the patients experience symptom relief after the first surgery, one-quarter after the second, and three-quarters of the remaining patients after the third surgery. This may be the result of multiple partial resections.