Skeletal "Dont touch" lesions

Question 1

posttraumatic lesion that should not undergo biospy because its aggressive histologic appearance can often mimic a sarcoma

Answer 1

myositis ossificans

Question 2

typical radiographic appearance of myositis ossificans

Answer 2

circumferential peripheral calcification with a lucent center

Question 3

occassionally, the peripheral calcification of myositis ossificans can be too faint to appreciate; in these cases a CT scan should help or else delayed radiographs ____ weeks later are recommended

Answer 3

1 to 2 weeks

Question 4

characteristic location of avulsion injuries

Answer 4

ligament and tendon insertion sites

Question 5

process on the medial supracondylar ridge of the distal femur that is considered by many to be the result of an avulsion of the adductor magnus muscle

Answer 5

cortical desmoid

Question 6

cortical desmoids occur only on the

Answer 6

posteromedial condyle of femur

Question 7

true or false: trauma can lead to large, cystic geodes or subchondral cysts near joints and can be mistaken for other lesions, resulting in a biopsy being ordered

Answer 7

true

Question 8

variant of Schmorl node. usually seen in middle-aged woman with chronic low back pain

Answer 8

discogenic vertebral sclerosis

Question 9

pathognomonic for myositis ossificans

Answer 9

peripheral calcification

Question 10

this results from fracture with hemarthrosis, which causes distention of the joint and migration of humeral head inferiorly

Answer 10

pseudodislocation of humerus

Question 11

lytic defect in the upper outer quadrant of patella

Answer 11

dorsal defect of patella (normal variant)

Question 12

caused by increase cancellous bone in the region of the greater tuberosity of the humerus that gives this region a more lucent appearance on radiographs

Answer 12

pseudocyst of humerus

Question 13

normal varinat of cervical spine that may, infact be posttraumatic is an_____. it is an unfused dens that may move anterior to the C2 body with flexion and can mimic a fractured dens

Answer 13

os odontoideum

Question 14

radiologic signs for recognizing an os odontoideum are

Answer 14

smooth, often well-corticated, inferior border of the dens and the hypertrophied, densely corticated anterior arch of C1

Question 15

identifcal to fibrous cortical defect, but the rem is usually reserved for defects larger than 2 cm. they are classically lucent lesions located in the cortex of metaphysis of a longe bone and have a well-defined, often sclerotic, scallpoed border with slight cortical expansion

Answer 15

nonossifying fibroma

Question 16

nonossifying fibroma is almost exclusively found in what age

Answer 16

younger than 30

Question 17

bone islands are usually of what size

Answer 17

1 cm or less

Question 18

what differentiates a bone island from sclerotic metastasis

Answer 18

bone islands are oblong with their long axis in the axis of stress on the bone, bony trabeculae is spiculated

Question 19

characteristic appearance of early bone infarcts

Answer 19

patchy demineralization or mixed sclerotic-lytic pattern

Question 20

unicameral bone cysts are often prophylactically curettaged and packed so as to prevent fracture with subsequent deformity. when these cysts occur in the _____, they should be left alone, because it is an area that does not receive undue stress

Answer 20

calcaneus

Question 21

characteristic MR appearance of a bone infarct

Answer 21

has serpiginous border