MSK: Random Trivia Flashcards
Liposclerosing myxofibroma
Note: Lucent lesion with sclerotic border in the intertrochanteric region.
Why is it important to follow liposclerosing myxofibroma?
10% undergo malignant degeneration (mostly to osteosarcoma)
What is the only benign skeletal tumor associated with radiation?
Osteochondroma
Osteochondroma
Can osteochondroma undergo malignant transformation?
Yes, to chondrosarcoma
How can you estimate the risk of an osteochondroma undergoing malignant degeneration?
Look at the size of the cartilage cap
Note: A cap > 1.5 cm is concerning for malignant transformation.
Osteochondromas of the posterior knee are associated with an increased risk of…
Popliteal artery pseudoaneurysm
How can you differentiate an osteochondroma from dysplasia epiphysealis hemimelica?
Osteochondromas are exostoses that point away from joints
Dysplasia epiphysealis hemimelica (AKA Trevor disease) involves exostoses that point into the joint, which is why they cause so many joint issues
Is there bone marrow within osteochondromas?
Yes, which is classically seen on T1 images
Multiple hereditary exostoses
An autosomal dominant condition with multiple osteochondromas (sessile and/or pedunculate)
Trevor disease
AKA dysplasia epiphysealis hemimelica: A disease characterized by the development of osteochondromas at the epiphysis which result in significant joint deformity (rather than pointing away from the joint like normal osteochondromas, these point into the joint and cause problems)
Treatment for dysplasia epiphysealis hemimelica (AKA Trevor disease)
Surgical excision of the epiphyseal osteochondromas that are causing joint problems
Think dysplasia epiphysealis hemimelica (AKA Trevor disease)
Note: Osteochondroma arising from an epiphysis (especially distal femur). These cause joint problems are are treated with surgical excision.
Dysplasia epiphysealis hemimelica (AKA Trevor disease)
Note: These cause joint problems are are treated with surgical excision.
Supracondylar spur (AKA Avian spur)
Note: This is a normal variant that can compress the median nerve. You know this is not an osteochondroma because it points towards the joint.
An Avian spur can lead to compression of the…
Median nerve (compression is by the ligament of Struthers, which attaches to the supracondylar spur)
Pediatric pt
Think periosteal chondroma (AKA junta-cortical chondroma)
8 y/o
Think osteofibrous dysplasia
Note: This looks like a nonossifying fibroma in the anterior tibia with associated tibial bowing in a pt under age 10. It occurs with Adamantinoma (cannot distinguish the two on imaging).
Cortical desmoid (AKA distal femoral metaphysis irregularity), a normal finding
Note: This is a lucency seen along the back of the posteromedial aspect of the distal femoral metaphysis. It is often bilateral. This is a normal finding (do not touch lesion, no MRI, no biopsy).
What is the most common location for hydroxyapatite deposition?
The shoulder (specifically the supraspinatus tendon)
Calcific tendonitis (calcium hydroxyapatite deposition disease)
Neck pain
Calcific tendonitis of the longus coli
What are the common causes of secondary calcific tendonitis?
- Chronic renal disease
- Collagen-vascular disease
- Tumoral calinosis
- Hypervitaminosis D
Osteopoikilosis (idiopathic or autosomal dominant development of numerous bone islands)
Note: Numerous bone islands centered around a joint (if bone islands are more randomly distributed, consider sclerotic metastases).
Pts with osteopoikilosis tend to be predisposed to ______ formation
Keloid
Osteopathia striata (linear parallel longitudinal lines in the metaphyses of long bones)
Note: This usually doesn’t mean anything but can be associated with pain.
Engelmann’s disease (AKA progressive diaphysial dysplasia)
Note: Fusiform bony enlargement and sclerosis of the long bone diaphyses. It is bilateral and symmetric.
Can Engelmann’s disease affect the skull?
Yes, where the bony enlargement/sclerosis can cause optic nerve compression
Bone scan
Engelmann’s disease (AKA progressive diaphysial dysplasia)
Note: Bilateral and symmetric fusiform sclerotic enlargement of the long bone diaphyses.
Thalassemia and sickle cell disease can both cause expansion of facial bones, but which one can actually obliterate the sinuses?
Thalassemia
Hair-on-end appearance of skull, which can be seen in thalassemia
Major causes of avascular necrosis of the femoral head
- Trauma
- Perthes (pediatrics)
- Sickle cell
- Gauchers
- Steroid use
Double line sign…
Avascular necrosis
Unstable avascular necrosis with osteochondral fragment
Note: This shows the “rim sign.”
Avascular necrosis
Note: This is the “crescent sign” that suggests imminent collapse.
What are the plain film stages of osteonecrosis?
0: Normal
1: Normal radiograph, edema on MRI
2: Mixed lytic/sclerotic
3: Crescent sign, articular collapse, joint space is preserved
4: Secondary osteoarthritis
What is the pattern of disease progression in Paget Disease (AKA osteitis deformans)?
Lytic -> mixed -> sclerotic
Note: The sclerotic phase is latent and inactive.
Wide bones with thick trabecula…
Think Paget disease
What are the two types of Paget disease?
- Polyostotic (90%)
- Monostotic
Clinical manifestations of the lytic phase of Paget disease
Usually asymptomatic
Clinical manifestations of the mixed (reparative) phase of Paget disease
- Elevated alkaline phosphatase
- Fractures
Clinical manifestations of the sclerotic (latent inactive) phase of Paget disease
- Elevated hydroxyproline
- Fracture (highest risk of all phases)
- Sarcomas may develop
Think Paget disease (lytic phase)
Note: This is the “blade of grass sign” (a Lucent leading edge in a long bone).
Osteoporosis circumscripta, suspicious for the lytic phase of Paget disease
Picture frame vertebrae, suggestive of the mixed phase of Paget disease (sclerotic border with Lucent center)
Rugger jersey vertebrae, suggestive of hyperparathyroidism (e.g. renal osteodystrophy)
Note: This is similar to sandwich vertebrae seen in osteopetrosis.
Cotton wool appearance, suggestive of the mixed phase of Paget disease
Note: This is due to thick, disorganized trabecula.
Banana fracture (insufficiency fracture in a bowed soft bone, usually femur or tibia), suggestive of Paget disease
Pagets disease
Note: Cotton wool appearance and “Tam O’Shanter sign” (frontal bone thickening that appears to fall over the facial bones, like a Tam O’Shanter hat).
Pages disease
Note: Saber shin (expansile bowing of the tibia).
Ivory vertebra, suggestive of Paget disease or sclerotic metastasis
Note: Pagets is usually expansile.
What is the most common complication of Pagets
Deafness
Common complications of Paget disease
- Deafness (most common)
- Spinal stenosis
- Cortical stress fracture
- Cranial nerve paresis
- High output CHF
- Secondary hyperparathyroidism
- Osteosarcoma
Paget disease increases the risk of what malignancy?
Osteosarcoma (occurs in 1% of cases)
Note: Osteosarcoma in the setting of Pagets is usually highly resistant to treatment.
Is Pagetoid bone more or less vascular than normal bone?
More vascular (an up to 5 degrees hotter) than normal bone
How can you differentiate Pagets from fibrous dysplasia in the setting of an expanded skull
Pagets has a cotton wool appearance and tends to involve both the inner and outer tables
Fibrous dysplasia is more ground glass and favors the outer table
What is the most common bone involved in Pagets?
Pelvis (always involving the iliopectineal line on the pelvic brim)
Note: This often leads to advanced arthritis and acetabular protrusio.
Major risk factor for Pagets
Age (4% prevalence at age 40 and 8% prevalence at age 80)
Osteopetrosis
A genetic disease with impaired osteoclastic resorption (resulting in thick cortical bone with diminished marrow)
Rugger Jersey spine with loss of the normal T1 marrow signal on MRI…
Think osteopetrosis
Note: Hyperparathyroidism in renal osteodystrophy will have the Rugger Jersey spine, but bone marrow signal should be normal.
H-shaped vertebrae, suggestive of sickle cell disease (due to microvascular endplate infarctions)
Note: Gauchers can also create this appearance.
Widening of the disc spaces…
Think sickle cell disease (this is another way to say H-shaped vertebrae)
Note: Gauchers can also have H-shaped vertebrae.
What is the MRI marrow pattern for Pagets disease in the lytic/early mixed phase?
- T1 isointense to muscle with a speckled appearance
- T2 heterogeneous
What is the MRI marrow pattern for Pagets disease in the late mixed phase?
Maintained fatty high T1 and T2 signal
What is the MRI marrow pattern for Pagets disease in the sclerotic phase?
Low signal on T1 and T2
Best sequence to differentiate active Paget disease from Paget malignant transformation
T1 pre contrast (malignant transformation should appear darker on T1 than active Paget disease)
Note: Both will enhance and both will appear bright on T2.
How does Paget disease appear on bone scan?
Usually 3 phase hot and involving the entire bones (e.g. if vertebral body is involved the posterior elements are usually also involved)
Note: Uptake may be normal/decreased in the late sclerotic phase.
18 m/o
Physiologic genu varum
Note: This is normal in pts 18 months to 2 years (should be smooth and bilateral).
Tibial bowing and fibular pseudoarthrosis, consistent with NF-1
Tibial bowing with wide growth plates and fraying of the metaphyses, consistent with Rickets
Blount disease (tibia vara)
Note: Growth disturbance of the posteromedial tibial physes. This is commonly seen in obese toddlers that start walking early.
