Osteoid osteoma
Updates to Article Attributes
Osteoid osteomas are benign bone tumours that typically occur in children (particularly adolescents). They have characteristic appearances and classically cause night-pain that is relieved by the use of salicylate analgesia, e.g. Aspirin.
Epidemiology
Osteoid osteomas are usually found in children and adolescents -, the vast majority of cases occur in patients between the ages of 10 and 35 years 2. They account for approximately 10% of all benign bone lesions and there is a male predilection (M:F 2-4:1) 2.
Clinical presentation
Classically patients present with nocturnal pain and is relieved by salicylates (e.g. Aspirin).
When in the spine they are a classic cause of a painful scoliosis. This typical presentation is seen in over 75% of cases 2.
Soft tissue swelling may occur (see case 4) and if close to a growth plate, accelerated growth may be evident 2 - presumably, presumably related to hyperaemia.
When the lesion is intra-capsular, presentation is more atypical, and more likely mimics and inflammatory arthropathy or synovitis. Joint effusion is often present 2,4.
Pathology
An osteoid osteoma is composed of three concentric parts 1:
- nidus
- meshwork of dilated vessels, osteoclasts, osteoid and woven bone
- may have a central region of mineralisation 2
- fibrovascular rim
- surrounding reactive sclerosis
The nidus releases protaglandins (via Cox-1 and Cox-2) which in turn result in pain 2.
Distribution
Most osteoid osteomas occur in long tubular bones of the limbs (especially proximal femur) but essentially any bone may be involved.
- long bones of the limbs:
~ 65~65-80% 1-2,8,7- femur most common (especially neck of femur)
- mid tibial diaphysis common also
- phalanges:
~ 20~20% - vertebrae:
~ 10~10%- lumbar: 59% 2
- cervical: 27%
- thoracic: 12%
- sacrum: 2%
Furthermore, osteoid osteomas can occur anywhere within the bone, including cortex, medulla or subperiosteal or even intra-capsular 2.
Radiographic features
It is important to remember that the sclerosis is reactive and does not represent the lesion itself. The nidus is usually less than 2 cm in diameter, and is typically ovoid. It may have a central region of mineralisation 2.
Plain film
May be normal or may show a diffuse periosteal reaction with cortical thickening. The nidus is sometimes visible as a well circumscribed lucent region, occasionally with a central sclerotic dot.
CT
Excellent at characterising the lesion and is the modality of choice. It typically shows a focally lucent nidus within surrounding sclerotic reactive bone. A central sclerotic dot may also be seen.
Scintigraphy
Will show typical focal uptake an at times will show a double density sign (also known as the less catchy hotter spot within hot area sign) which if present is highly specific. The central focus showing intense uptake within a surrounding lower, but nonetheless increased uptake, rim.
Ultrasound
On ultrasound, focal cortical irregularity with adjacent hypoechoic synovitis may be present at the site of intra articular lesions. The nidus can show hypoechogenecity with posterior acoustic enhancement. Ultrasoundmay may be able to identify the nidus as a hypervascular nidus on doppler examination 2.
MRI
Although MRI is certainly sensitive, it is non-specific often unable to identify the nidus. The hyperaemia and resultant bone marrow oedema pattern may result in the scans being misinterpreted as representing aggressive pathology 2.
The signal intensity of the nidus is variable on all sequences as is the degree of contrast enhancement 2.
Treatment and prognosis
The lesion is benign and treatment has traditionally been with surgical resection. Historically, this has, on occasion, been difficult because of the inherent inability to locate the nidus during surgery 3. However, percutanous radiofrequency ablation is being used under CT guidance is being used with increasing frequency 5.
There is growing evidence, that osteoid osteoma finally resolves spontaneously over time and can be treated conseratively with NSAIDs in certain groups of patients6. Average time to resolution is 33 months7
Differential diagnosis
General imaging differential considerations include:
- osteomyelitis (e.g Brodie abscess): bone scan demonstrates central area of reduced uptake representing an avascular area of purulent material.
-
osteoblastoma: >
; 2;2 cm in size - stress fracture
- cortical desmoid
- osteochondroma
- osteosarcoma
- enostosis
-<p><strong>Osteoid osteomas</strong> are <a href="/articles/benign-bone-tumours">benign bone tumours</a> that typically occur in children (particularly adolescents). They have characteristic appearances and classically cause night-pain that is relieved by the use of salicylate analgesia, e.g. Aspirin.</p><h4>Epidemiology</h4><p>Osteoid osteomas are usually found in children and adolescents - the vast majority of cases occur in patients between the ages of 10 and 35 years <sup>2</sup>. They account for approximately 10% of all <a href="/articles/benign-bone-lesions">benign bone lesions</a> and there is a male predilection (M:F 2-4:1) <sup>2</sup>.</p><h4>Clinical presentation</h4><p>Classically patients present with nocturnal pain and is relieved by salicylates (e.g. Aspirin).</p><p>When in the spine they are a classic cause of a painful scoliosis. This typical presentation is seen in over 75% of cases <sup>2</sup>.</p><p>Soft tissue swelling may occur (see case 4) and if close to a growth plate, accelerated growth may be evident <sup>2</sup> - presumably related to hyperaemia.</p><p>When the lesion is intra-capsular, presentation is more atypical, and more likely mimics and inflammatory arthropathy or synovitis. Joint effusion is often present <sup>2,4</sup>.</p><h4>Pathology</h4><p>An osteoid osteoma is composed of three concentric parts <sup>1</sup>:</p><ol>- +<p><strong>Osteoid osteomas</strong> are <a href="/articles/benign-bone-tumours">benign bone tumours</a> that typically occur in children (particularly adolescents). They have characteristic appearances and classically cause night-pain that is relieved by the use of salicylate analgesia, e.g. Aspirin.</p><h4>Epidemiology</h4><p>Osteoid osteomas are usually found in children and adolescents, the vast majority of cases occur in patients between the ages of 10 and 35 years <sup>2</sup>. They account for approximately 10% of all <a href="/articles/benign-bone-lesions">benign bone lesions</a> and there is a male predilection (M:F 2-4:1) <sup>2</sup>.</p><h4>Clinical presentation</h4><p>Classically patients present with nocturnal pain and is relieved by salicylates (e.g. Aspirin).</p><p>When in the spine they are a classic cause of a painful scoliosis. This typical presentation is seen in over 75% of cases <sup>2</sup>.</p><p>Soft tissue swelling may occur (see case 4) and if close to a growth plate, accelerated growth may be evident <sup>2</sup>, presumably related to hyperaemia.</p><p>When the lesion is intra-capsular, presentation is more atypical, and more likely mimics and inflammatory arthropathy or synovitis. Joint effusion is often present <sup>2,4</sup>.</p><h4>Pathology</h4><p>An osteoid osteoma is composed of three concentric parts <sup>1</sup>:</p><ol>
-<li>long bones of the limbs: ~ 65-80% <sup>1-2,8</sup><ul>- +<li>long bones of the limbs: ~65-80% <sup>1-2,7</sup><ul>
-<li>phalanges: ~ 20%</li>-<li>vertebrae: ~ 10%<ul>- +<li>phalanges: ~20%</li>
- +<li>vertebrae: ~10%<ul>
-</ul><p>Furthermore, osteoid osteomas can occur anywhere within the bone, including cortex, medulla or subperiosteal or even intra-capsular <sup>2</sup>.</p><h4>Radiographic features</h4><p>It is important to remember that the sclerosis is reactive and does not represent the lesion itself. The nidus is usually less than 2 cm in diameter, and is typically ovoid. It may have a central region of mineralisation <sup>2</sup>.</p><h5>Plain film</h5><p>May be normal or may show a diffuse periosteal reaction with cortical thickening. The nidus is sometimes visible as a well circumscribed lucent region, occasionally with a central sclerotic dot.</p><h5>CT</h5><p>Excellent at characterising the lesion and is the modality of choice. It typically shows a focally lucent nidus within surrounding sclerotic reactive bone. A central sclerotic dot may also be seen.</p><h5>Scintigraphy</h5><p>Will show typical focal uptake an at times will show a <a href="/articles/double-density-sign-of-osteoid-osteoma">double density sign</a> (also known as the less catchy <a href="/articles/hotter-spot-within-hot-area-sign">hotter spot within hot area sign</a>) which if present is highly specific. The central focus showing intense uptake within a surrounding lower, but nonetheless increased uptake, rim.</p><h5>Ultrasound</h5><p>On ultrasound, focal cortical irregularity with adjacent hypoechoic synovitis may be present at the site of intra articular lesions. The nidus can show hypoechogenecity with posterior acoustic enhancement. Ultrasound <span style="line-height:1.6em">may be able to identify the nidus as a hypervascular nidus on doppler examination </span><sup style="line-height:1.6em">2</sup><span style="line-height:1.6em">.</span></p><h5>MRI</h5><p>Although MRI is certainly sensitive, it is non-specific often unable to identify the nidus. The hyperaemia and resultant bone marrow oedema pattern may result in the scans being misinterpreted as representing aggressive pathology <sup>2</sup>.</p><p>The signal intensity of the nidus is variable on all sequences as is the degree of contrast enhancement <sup>2</sup>.</p><h4>Treatment and prognosis</h4><p>The lesion is benign and treatment has traditionally been with surgical resection. Historically, this has, on occasion, been difficult because of the inherent inability to locate the nidus during surgery <sup>3</sup>. However, percutanous <a href="/articles/radiofrequency-ablation">radiofrequency ablation</a> is being used under CT guidance is being used with increasing frequency <sup>5</sup>.</p><p>There is growing evidence, that osteoid osteoma finally resolves spontaneously over time and can be treated conseratively with NSAIDs in certain groups of patients<sup>6</sup>. Average time to resolution is 33 months<sup>7</sup>.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include</p><ul>- +</ul><p>Furthermore, osteoid osteomas can occur anywhere within the bone, including cortex, medulla or subperiosteal or even intra-capsular <sup>2</sup>.</p><h4>Radiographic features</h4><p>It is important to remember that the sclerosis is reactive and does not represent the lesion itself. The nidus is usually less than 2 cm in diameter, and is typically ovoid. It may have a central region of mineralisation <sup>2</sup>.</p><h5>Plain film</h5><p>May be normal or may show a diffuse periosteal reaction with cortical thickening. The nidus is sometimes visible as a well circumscribed lucent region, occasionally with a central sclerotic dot.</p><h5>CT</h5><p>Excellent at characterising the lesion and is the modality of choice. It typically shows a focally lucent nidus within surrounding sclerotic reactive bone. A central sclerotic dot may also be seen.</p><h5>Scintigraphy</h5><p>Will show typical focal uptake an at times will show a <a href="/articles/double-density-sign-of-osteoid-osteoma">double density sign</a> (also known as the less catchy <a href="/articles/hotter-spot-within-hot-area-sign">hotter spot within hot area sign</a>) which if present is highly specific. The central focus showing intense uptake within a surrounding lower, but nonetheless increased uptake, rim.</p><h5>Ultrasound</h5><p>On ultrasound, focal cortical irregularity with adjacent hypoechoic synovitis may be present at the site of intra articular lesions. The nidus can show hypoechogenecity with posterior acoustic enhancement. Ultrasound may be able to identify the nidus as a hypervascular nidus on doppler examination <sup>2</sup>.</p><h5>MRI</h5><p>Although MRI is certainly sensitive, it is non-specific often unable to identify the nidus. The hyperaemia and resultant bone marrow oedema pattern may result in the scans being misinterpreted as representing aggressive pathology <sup>2</sup>.</p><p>The signal intensity of the nidus is variable on all sequences as is the degree of contrast enhancement <sup>2</sup>.</p><h4>Treatment and prognosis</h4><p>The lesion is benign and treatment has traditionally been with surgical resection. Historically, this has, on occasion, been difficult because of the inherent inability to locate the nidus during surgery <sup>3</sup>. However, percutanous <a href="/articles/radiofrequency-ablation">radiofrequency ablation</a> is being used under CT guidance is being used with increasing frequency <sup>5</sup>.</p><p>There is growing evidence, that osteoid osteoma finally resolves spontaneously over time and can be treated conseratively with NSAIDs in certain groups of patients <sup>6</sup>. Average time to resolution is 33 months.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>
-<a href="/articles/osteoblastoma">osteoblastoma</a>: > 2 cm in size</li>- +<a href="/articles/osteoblastoma">osteoblastoma</a>: >2 cm in size</li>
References changed:
- 7. K. Krishnan Unni, Carrie Y. Inwards. Dahlin's Bone Tumors. (2010) ISBN: 9780781762427 - <a href="http://books.google.com/books?vid=ISBN9780781762427">Google Books</a>
- 7. Article from bonetumor.org <a href="http://www.bonetumor.org/tumors-bone/osteoid-osteoma">Bonetumor.org</a>
- 8. Unni KK, Inwards CY, Research MF. Dahlin's bone tumors, general aspects and data on 10,165 cases. Lippincott Williams & Wilkins. (2009) ISBN:0781762421. <a href="http://books.google.com/books?vid=ISBN0781762421">Read it at Google Books</a> - <a href="http://www.amazon.com/gp/product/0781762421?ie=UTF8&tag=radiopaediaor-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=0781762421">Find it at Amazon</a><div class="ref_v2"></div>
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