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35 Cards in this Set

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Myositis ossificans is differentiated from osteogenic sarcoma by?
both look like calcified fluffy lesions but myositis ossificans has a circumferential nature.
If it is hard to tell if a lesion looking like myositis offisficans is circumferential what do you do?
CT or delayed repeat films 1 or 2 weeks
What can you do to determine if a lesion is an avulsion injury vs malignancy? (2)
Repeat films in several weeks. Also location is helpful (at ligament and tendon insertion sites)
two is a finding
What is a cortical desmoid?
a process on the medial supracondylar ridge of the distal femur that is considered to be an avulsion of adductor magnus muscle. It can simulate an aggresive lesion.
1. What is the characteristic radiographic findings of cortical desmoid?
2. What are other findings (history, p.e.)?
1. Occur only at the posteromedial epicondyle of the femur, might or might not have periosteal reaction, have increased radionuclide uptake on bone scan, Often found as incidental findings on MR of knee and have characteristic appearance.
2. might or might not be assoc with pain which should go away at rest. usually occur in young people.
1. three things
2. three things
What is the MR appearance of a cortical desmoid that is characteristic?
faint lytic leasion in the medial aspect of the distal femur more specifically in the medial supracondylar ridge.
Trauma lesion mimicking malignancy? (3 examples)
1. Geode's. biopsy does not, in this case, look like malignancy histologically. However this shouldn't occur because geode's always come with other radiographic findings that give away that it is benign (oa findings OR other instances having geode's such as ra, avn, CPPD - calcium pyrophosphate dihydrate deposition dz)
2. Fracture that is not immobilized can have extensive periostitis and osteosclerosis (lack of immobilization creates an exuberant callus)
3. Pseudo-dislocation of the humerus (from fracture and hemarthrosis causing inferior sublux but not dislocation)
Three of them.
Focal sclerosis of vertebrae in the region of the endplate in the setting of disk space narrowing and osteophytosis is what?
Discogenic Vertebral Sclerosis...should not be boipsied
Typical clinical setting of discogenic vertebral sclerosis?
Middle aged woman with chronic back pain
What can help in proving a vertebral sclerotic lesion is discogenic vertebral sclerosis?
clinical history, old films, and typical radiographic findings
Normal variants that can mimic aggressive lesions... (3 examples)
1. dorsal defect of the patella
2. pseudocyst of the humerus
3. os odontoideum
arm, knee, neck
Dorsal defect of the patella...describe it and what three things does it mimic?
"upper outer quadrant" lytic lesion. It can mimic focus of infection, osteochondritis dissecans or chondroblastoma
Pseudocyst of the humerus...describe and what three example things can it mimic?
area of increased cancellous bone in the region of the greater tuberosity of the humerus giving it more lucent appearance. Can mimic infection, chondroblastoma or mets.
What can occur to a pseudocyst of the humerus to trigger biopsy and excision?
hyperemia and increased uptake on bone scan secondary to a rotator cuff injury...biopsy looks like aggressive lesion.
Os odontoideum...what is it and what are the findings?
1. Non-union of dens to rest of C2. 2. Anterior sublux of C1 on flexion,
3. no neuro sx,
4. well corticated dens fragment,
5. hypertrophied, densely corticated anterior arch of C1.
Why is recognizing Os odontoideum important for the radiologist.
This is not an emergency and can be fixed electively...saved patient from the halo.
List 4 "obviously benign (don't touch) lesions"
Bone island
Unicameral bone cyst
Bone infarction
Non ossifying fibroma (NOF) vs fibrous cortical defect.
Same thing only NOF's are >2cm.
Describe findings of an NOF? (location, rad appearance)
1. lytic lesion in cortex of metaphysis of a long bone
2. well defined, often sclerotic, scalloped border
3. slight cortical expansion.
What age group do you find NOF's?
<30...natural history is involution/fill with new bone = sclerotic appearance after 30 and increased radionuclide activity.
What are NOF's mostly mistaken for?
infection, EG,fibrous dysplasia, abc.
Can NOF's degenerate into malignancy?
Do surgeon's advocate prophylactic curettage of NOF's?
No..this is unlike unicameral bone cysts.
Bone islands usual size...
1cm or smaller...but occasionally they grow to golf ball size or larger.
What can large bone islands mimic? List one way to differentiate them on physical exam.
Sclerotic mets...but they are always asymptomatic.
Two ways to distinguish large bone island radiographically...
1. usually oblong with long axis in the axis of stress on the bone
2. margins when examined closely show bony trabeculae extending from the lesion into the normal bone in a spiculated fashion
Unicameral bone do you treat?
often prophylactically curettaged and packed to prevent fracture unless in the calcaneus.
Why aren't unicameral bone cysts curettaged when in the calcaneus?
they are always anteroinferior where there is little stress.
Radiographic characteristics of unicameral bone cysts...(6 but 3 classic B and H)
1. ALWAYS central (only FEGNOMASHIC lesion that is always central)
3. One of the few lesions that does not occur most commonly around the knees. Can occur in any bone. Common site calcaneus. 2/3 to 3/4 occur in proximal humerus and femur.
4. Fallen fragment sign (post fracture)
5. Begin at physeal plate in long bones and grow into shaft. Can later grow into epiphysis but usually wont.
5. No periositis
6. Must be younger than 30.
Other names for unicameral bone cyst? three
simple bone cyst or solitary bone cyst are the same thing. unicameral = one compartment.
Radiographic appearance of bone infarcts...(2)
1. Early on they are patchy or mixed lytic-sclerotic pattern
2. Can also even have a permeative look...scary because looks like aggressive lesion then.
Bone can you differentiate from aggressive lesions?
1. multiple
2. diametaphyseal region of long bone
3. underlying disorder
4. MR
What does one see on MR with bone infarcts?
characteristic serpiginous border.
What underlying disorders would make you think of bone infarct? (2)
sickle cell, SLE
Where do you commonly get pseudo-cysts and why?
Pseudocysts are in areas of low stress...anteroinferior calcaneus...(this is also where you get unicameral bone cysts commonly), and humerus greater troch.