MSK: Osteoporosis, Osteopenia, and AVN Flashcards
Osteomalacia
Soft bone due to excessive unmineralized osteoid, usually related to vitamin D issues (e.g. renal failure, liver disease, etc.)
Imaging findings of osteomalacia
- Ill-defined trabeculae
- Ill-definted corticomedullary junction
- Bowing of the bones
- Looser zones (a subtype of insufficiency fracture)
Looser zones (lucent bands that run perpendicular to the cortex with surrounding sclerosis)
Note: These are a type of insufficiency fracture commonly seen at the femoral neck and pubic rami.
Looser zones (a type of insufficiency fracture)
Differential for looser zones
- Osteomalacea
- Rickets
- Osteogenesis imperfecta (rare)
Imaging findings of osteoporosis
- Thin sharp cortex
- Prominent trabecular bars
- Lucent metaphyseal bands
- Spotty lucencies
What are the most common fractures in the setting of osteoporosis?
- Spine (most common)
- Hip (2nd)
- Wrist (3rd)
What is the DEXA T score relative to?
A young adult
What is the T score that defines osteoporosis?
T score less than -2.5
Note: T score of -1.0 to -2.5 is osteopenia.
What should a normal DEXA T score be?
Above -1.0
What is the DEXA Z score relative to?
An age-matched database
Common cause of a false positive DEXA
Absence of normal structures (e.g. laminectomies)
Common causes of false negatives on DEXA
- Including high density things that shouldn’t be included (e.g. Sclerosis, osteophytes, dermal calcifications, metal objects, etc.)
- Including too much of the femoral shaft while measuring the hip
What does the FRAX tool estimate?
10-year probability of a major fracture
Note: Pts with an elevated FRAX might benefit from therapy even if they are only osteopenic.
What is considered an elevated FRAX score (meaning treatment should be considered even though they aren’t osteoporotic)?
> 3% risk of hip fracture
Or
> 20% risk of major fracture
What are the most common sites involved in reflex sympathetic dystrophy (AKA complex regional pain syndrome)?
Hands and shoulders
Chronic right hand pain following a remote fracture…
Reflex sympathetic dystrophy (AKA complex regional pain syndrome)
Note: Periarticular osteopenia distal to a right radial fracture.
Chronic left wrist pain
Reflex sympathetic dystrophy (AKA complex regional pain syndrome)
Imaging findings of reflex sympathetic dystrophy (AKA chronic regional pain syndrome)
- Regional severe osteopenia with preserved joint spaces
- 3 phase hot region on bone scan (intraarticular uptake is classic due to increased vascularity of the synovial membrane)
What are the two major types of transient osteoporosis?
- Transient osteoporosis of the hip
- Regional migratory osteoporosis
30 y/o F with third trimester pregnancy
Transient osteoporosis of the hip
Note: This will resolve in a few months.
Third trimester pregnancy
Transient osteoporosis of the hip
Note: This will resolve in a few months.
Third trimester pregnancy
Transient osteoporosis of the hip
Note: This will resolve in a few months.
50 y/o M with joint pain associated with focal osteoporosis that gets better, but then shows up again in a different joint…
Regional migratory osteoporosis
Note: This is self-limiting and more common in males than females.
Avascular necrosis of the right femoral head
Avascular necrosis of the left femoral head
Subchondral insufficiency fracture
Note: Avascular necrosis should have a more serpiginous dark line that doesn’t parallel the subchondral bone.
Post contrast
Malignant vertebral compression fracture
Note: Avid enhancement that extends beyond the deformed bone with an expanded posterior convex border. Osteoporotic compression fractures typically result in a more band-like appearance.
Benign vertebral compression fracture
Note: There is a linear, horizontal fracture line. If there were nonlinear abnormal marrow signal with involvement of the posterior margin, then you should think about malignancy.
Think malignant replacement of bone marrow
Note: Normally the vertebral body bone marrow should be brighter than adjacent intervertebral discs on TI.
Next step:
Image the entire spine (looking for other metastases)
Osteochondritis dissscans
Aseptic separation of an osteochondral fragment from the underlying bone that can lead to gradual fragmentation of the articular surface and secondary osteoarthritis
Note: Most of the time this is secondary to trauma or avascular necrosis.
Osteochondritis dissecans is most common in what pt population?
Males under age 18
What is the most classic location for osteochondritis dissecans?
- Femoral condyle
- Patella
- Talus
- Capitellum
What is the staging system for osteochondritis dissecans?
Stage 1: Stable (covered by intact cartilage, continuous with host bone)
Stage 2: Stable on probing, partial discontinuity with host bone
Stage 3: Unstable on probing, complete discontinuity of lesion
Stage 4: Dislocated fragment
What imaging feature should you look for to suggest that an osteochondral lesion is unstable?
High T2 signal between the osteochondral fragment and underlying bone
Note: Edema can cause a false positive.
What is a common location for osteochondritis dissecans in pitchers?
The capitellum of the dominant arm (specifically the anterior convex margin)
Note: Image shows osteochondral dissecans (yellow arrow) and loose body formation (red arrow).
Pseudo-defect of the posterior capitellum
Note: The posterior capitellum can appear to have an osteochrondral defect on coronal images when you are actually just seeing the non-articular portion of the capitellum (look at sagittal images to confirm).
Panner disease
Osteochondrosis of the capitellum (developmental disorder of the growing capitellum epiphysis)
Note: This occurs in younger males (7-12 y/o) compared to osteochondritis dissecans, which usually occurs in males age 12-16.
9 y/o male pitcher with lateral elbow pain
Panner’s disease (developmental disorder of the growing capitellum epiphysis)
Note: This involves the entire capitellum and occurs in younger males (7-12 y/o) compared to osteochondritis dissecans, which usually occurs in males age 12-16.
Osteochondroses
Developmental disorders of a growing epiphysis/apophysis with findings of collapse, sclerosis, and fragmentation (suggesting avascular necrosis)
Note: These are seen in childhood.
Male 4-6 y/o
Kohl’s disease (osteochondrosis of the taller navicular)
Note: Treatment is not surgical.
Adolescent female
Freiberg infraction (osteochondrosis of the second metatarsal head)
Note: This can lead to secondary osteoarthritis.
Sever’s disease (AKA calcaneal apophysitis)
Note: This represents osteochondrosis of the calcaneal apophysis. Some people think this is a normal finding.
Pediatric pt age 4-8
Legg-Calve-Perthes disease (osteochondrosis os the femoral head)
Adults age 20-40
Kienbock disease (osteochondrosis of the lunate)
Note: This is associated with negative ulnar variance.
Scheuermann disease (osteochondrosis of the thoracic spine leading to wedging of 3 adjacent levels and exaggerated thoracic kyphosis)
Pediatric pt age 10-15
Osgood-Schlatter disease (osteochondrosis of the tibial tubercle)
Note: This is commonly seen in kids who jump and kick a lot.
Pediatric pt age 10-15
Sinding-Larsen-Johansson disease (osteochondrosis of the inferior patella)
Note: This is commonly seen in kids who jump a lot.
