Osteoid osteoma

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Compiled from Yochum and Rowe here I discuss the radiological findings of osteoid osteoma

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Osteoid osteoma:

Osteoid osteoma Source: Yochum and Rowe Dr. Varun

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Henry Jaffe 1925. 11% of benign tumors 10-25 years. M:F = 2:1 Dr. Varun

SIGNS AND SYMPTOMS :

SIGNS AND SYMPTOMS Classic description – night pain relieved by aspirin Gradual onset of increasingly severe, deep, aching pain, a/w vasomotor disturbances, mainly profuse sweating and increased skin temperature in the affected region. Invariably referred to rheumatologist with pain being referred to nearby joint. Dr. Varun

SIGNS AND SYMPTOMS :

SIGNS AND SYMPTOMS Painful rigid scoliosis when seen on the concave side of the curve in thoracic or lumbar osteoid osteoma Torticollis and secondary contraction of sternomastoid in cervical osteoid osteoma . Spinous process lesions produce localized pain and spinal stiffness. Proximal femure or lumbar vertebrae may simulate a herniated disc Dr. Varun

LOCATION :

LOCATION Metaphyseal , diaphyseal 50% in femur and tibia. Upper femur, neck and trochanters . 10% in spine, most affecting neural arch (lamina>pedicle>facet> spinous process) Others: ribs, clavicle, humerus , fibula, mandible, skull, carpals and thumb. Dr. Varun

PATHOLOGIC FEATURES :

PATHOLOGIC FEATURES Soft, reddish brown vascularized nidus , usually <1cm diameter. Lucent on radiograph with a significant reactive sclerosis and cortical thickening (solid periosteal response surrounding the nidus ). Nidus usually uncalcified , may develop a fleck. Micro: small spherical nodules of highly vascularized fibrous connective tissue, with benign giant cells in an interlacing network of osteoid trabeculae (thin with variable mineralization) Dr. Varun

RADIOLOGICAL FEATURES :

RADIOLOGICAL FEATURES Lucent nidus with surrounding florid perifocal reactive sclerosis (cortical placed OO) Initially oval/round lucent nidus with surrounding increased bone density <1cm. The excess surrounding sclerosis may obscure the nidus . Occasionally central fleck of calcification is seen. When XRays are negative, plain CT identifies the lesion Dr. Varun

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Dr. Varun A. AP Tibia. Observe the radiolucent tumor nidus within the central medullary portion of the distal tibia ( arrow ). There is significant reactive sclerosis of bone surrounding the radiolucent nidus , some of which is periosteal new bone formation, assuming a solid pattern ( arrowheads ). B. Lateral Tibia. Note the significant cortical and periosteal new bone formation on the posterior surface of the distal tibia ( arrows ). The tumor nidus of the osteoid osteoma is not clearly visualized on this projection.

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Intramedullary lesions that are intracapsular are difficult to detect as the reactive sclerosis is minimal because of low bone production. Hence only the lucent nidus is seen making detection difficult Dr. Varun

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Dr. Varun Clavicle. Note the large, radiolucent tumor nidus in the mid- diaphysis of the clavicle ( arrow ). There is exuberant reactive sclerosis around the tumor nidus , creating bone expansion and enlargement of the clavicle ( arrowhead ). This is a rare location for osteoid osteoma .

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Dr. Varun AP Knee. Note the ill-defined area of increased cortical new bone in the medial metaphysis of the proximal tibia ( arrow ). B. Tomogram, AP Tibia. Observe that the previously noted reactive sclerosis in the medial cortical surface of the tibia is visualized. A small radiolucent tumor nidus is also seen ( arrow ). COMMENT: This patient presented with pain that was worse at night and that was dramatically relieved by the use of aspirin. This is the characteristic history of patients with both osteoid osteoma and Brodie’s abscess.

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Spinal lesions Usually produces pain before radiographic changes Neural arch – classical location. Detected in CT and increased uptake in bone scan Lumbar>cervical>thoracic>sacral Initial nidus undetected. Reactive sclerosis appears as dense/ivory pedicle or lamina, typically on concave side of a painful scoliosis. D/D: unilateral spondylolysis , congenital agenesis of contralateral pedicle, osteoblastoma , osteoblastic mets . Vertebral body lesions rare – ivory vertebra or focal sclerosis close to the end plate. Dr. Varun

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Dr. Varun Femoral Neck. Note the well-defined radiolucent tumor nidus within the neck of the proximal femur ( arrow ). A significant degree of reactive sclerosis of bone is seen adjacent to the tumor nidus ( arrowheads ), with the greatest changes seen caudal to the radiolucent nidus . This is a characteristic presentation for osteoid osteoma at this site.

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Angiography Intensely homogeneous vascular blush in the arterial phase and persisting late into venous phase. Distinguish from Brodie’s abscess, which shows no blush Plain radiograph provides diagnosis in >75% cases. Else plain CT. if negative, bone scan, then MRI Bone scan – regional increase in uptake with an intense focal zone of uptake superimposed (double density sign) MRI – marrow edema which increases the conspicuity of the nidus . Dr. Varun

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Observe the radiolucent nidus in the sub-endplate region ( arrow ). Reactive sclerosis extends into the vertebral body. Dr. Varun

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Proximal Femur. Observe the subtle radiolucent tumor nidus just inferior to the lesser trochanter ( arrow ). The minimal reactive sclerosis that surrounds this lesion is hard to perceive because of the confluence of the cortex at this anatomic site Dr. Varun

DIFFERENTIAL DIAGNOSIS :

DIFFERENTIAL DIAGNOSIS Garre’s chronic sclerosing osteomyelitis Disregarded as a distinct disease process as many previously described such conditions were in fact osteomas Brodie’s abscess Night pain relieved by aspirin Nidus >1cm Thicker irregular halo rim of sclerosis Angiographic vascular blush is absent Stress fracture Sequential studies over time and images demonstrate healing of the fracture Dr. Varun

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Observe the densely radiopaque pedicle of the L3 vertebra ( arrow ). This 12-year-old patient presented with pain that was worse at night and was dramatically alleviated by aspirin Dr. Varun

TREATMENT AND PROGNOSIS :

TREATMENT AND PROGNOSIS No treatment as it is self limiting. If pain beyond relief by NSAIDs then Radiotherapy and thermocoagulation Surgery: wide en bloc excision with removal of small portion of surrounding sclerotic bone. Recurrence is rare Spontaneous regression is reported, however patients usually don’t tolerate pain for that long Spinal lesions: excision, body lesions - RT Dr. Varun

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