Musculoskeletal #15 – Flashcard

This is the third and last case of the musculoskeletal series. Check the first one and second one on this blog.

What do you see on the following images?

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Osteoblastoma: Osteoblastoma is histologically similar to osteoid osteoma but they are larger (usually accepted more than 1 cm), often involving the posterior column

Musculoskeletal #12 – Flashcard

43-year-old healthy patient:
– with fibromyalgia
– No other relevant medical history

What do you see on the following images?

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IMAGING FINDINGS:

Multiple focal sclerotic bone lesions clustered around joints in both knees and sacroiliac joints

DIAGNOSIS:

Osteopoikilosis

TEACHING POINTS:

Sclerosing bony dysplasia characterized by multiple enostoses
Typically clustered around joints, aligned parallel to trabeculae. Usually 1-3 mm, they can reach up to 20 mm
Rare condition; inherited; asymptomatic; incidental
Important to avoid misdiagnosis with other relevant pathologies such as metastasis

Musculoskeletal #11

68-year-old male:
* Presents with a mass around knee which has been present for seven years and has been enlarging since then

What do you see?

A sclerotic ill-defined soft tissue mass around the knee was present on radiographs.
The mass is located in the soft tissue around the knee with no apparent bone destruction.

Coronal fat-suppressed T2 WI (a) shows a hyperintense lobulated mass which was hypointense on T1 WI (b) and has peripheral heterogeneous enhancement on postcontrast T1 WI (c); cortical bone is preserved.

The mass encircles a pedunculated lesion which continues with cortical and medullary bone (arrows), consistent with an osteochondroma.
Histopathologic diagnosis of the mass is chondrosarcoma.

Osteochondromas

* Osteochondromas are developmental lesions rather than true neoplasms and are often referred to as an osteocartilaginous exostosis (or simply exostosis).
* An osteochondroma is composed of cortical and medullary bone protruding from and continuous with the underlying bone; cortical and medullary continuity between the osteochondroma and parent bone is well depicted on MRI.
* Malignant transformation, almost invariably due to chondrosarcoma arising in the cartilage cap of the lesion, occurs in approximately 1% of solitary osteochondromas.
* Lesions that grow or cause pain after skeletal maturity should be suspected of malignant transformation since osteochondromas only rarely enlarge after this time.

Musculoskeletal #10 – Flashcard

29-year-old long-distance athlete presenting with 3 weeks of sciatica associated with an increase of running training loads

What do you see?

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IMAGING FINDINGS:

Unilateral sacral bone edema T2W, STIR hyperintensity associated with hypointense fracture line

DIAGNOSIS:

Fatigue stress fracture

TEACHING POINTS:

The sacrum is a frequent site for stress fractures
They can be related to overload occurring in a healthy bone as in this case, or related to osteoporosis (insufficiency stress fractures) in which cases they tend to be bilateral and “h- shaped”

Musculoskeletal #9 – Flashcard

12-year-old boy, asymptomatic:

Radiograph a

Radiograph b

What do you see?

Lytic lesion on distal fibular metaphysis with well-defined sclerotic borders is seen on both anteroposterior (a) and oblique (b) radiographs

What do you see?

NOF: non ossifying fibroma

– Most common fibrous bone lesion
– Same as fibrous cortical defect but larger version
– If large enough, may cause pathological fractures
– One of DON’T TOUCH lesions

Musculoskeletal #8 – Flash card

What do you see on the following images?

CT scout view

CT soft tissue window

CT bone window

Click here to see the answer

Skull eosinophilic granuloma
Well defined lytic lesion with scalloped edges. It involves both the inner and outer table. Narrow zone of transition, no cortical breakthrough and no soft tissue component.

Musculoskeletal #7 – Long case

10-year-old male:

Axial CT brain bone windows

Non-enhanced axial CT brain soft tissue window

Where is the lesion?

Occipital bone within the medullary cavity

What is it like?

Moth-eaten destructive permeative lytic lesion with wide zone of transition.  There is cortical disruption of both the inner and outer table of the skull and a large soft tissue component.

An MRI is performed.
Axial T1Weighted

Axial T2Weighted
Axial Gadolinium enhanced T1Weighted
What does the MRI show?

Destructive bone lesion with a large soft tissue component which is low signal intensity on T1, heterogenous intermediate signal on T2, and heterogeneous intense enhancement in the post contrast image. It causes mass effect on the adjacent brain parenchyma with no gross invasion.

What is the differential diagnosis?

Given the age of the patient the differential diagnosis includes:

* Osteosarcoma: most common primary bone tumor in young adults. Usually involves the metaphyseal regions of long bones but can occur at other sites. Aggressive lesion with sunburst periosteal reaction and calcified osteoid matrix. 

* Ewing's sarcoma: second most common childhood bone tumor. Typically an aggressive permeative tumor which arises within the medullary cavity of the bone and has a large soft tissue component. 

* Metastasis.

What is the most likely diagnosis?

Ewing’s sarcoma

Musculoskeletal #6 – Flashcard

28 year-old male with a history of shoulder dislocation.

Regarding this image:

What do you see?

Hill-Sachs lesion
* Edema on posterolateral humeral head secondary to compression fracture, well-demonstrated on axial fat suppressed proton density Weighted image
* Secondary to anterior dislocation of shoulder

Regarding this image:

What do you see?

Bankart lesion
* Tear/injury of anteroinferior labrum, well-demonstrated on axial fat suppressed proton density Weighted image
* Secondary to anterior dislocation of shoulder
* May have associated bony component