Bones and Arthritis Flashcards
Normal bone in plain radiography
When viewed in tangent, the cortex is seen as a smooth, white line, varying in thickness in different parts of the bone ( white arrows ).
The medullary cavity lies within the cortical shell and contains an interlacing network of trabeculae ( white circle).
The corticomedullary junction is the interface between the inner margin of the cortex and the medullary cavity ( solid black arrow ) .
Diagram, x-ray, and CT of the knee joint
Avascular necrosis of the femoral head
Avascular necrosis of the humeral head
What is going on in this patient’s femur?
This patient had an old medullary infarct
These appear as dense, amorphous deposits of bone within the medullary cavities of long bones, frequently marginated by a thin, sclerotic membrane
What is going on in this patient’s pelvic radiograph?
This is Paget’s disease of bone
Note the accentuation and coarsening of the trabeculae and the thickening of the cortex
Pattern of bone loss in hyperparathyroidism
Predominately subperiosteal and asymmetric in distribution, as shown in this image, with relative sparing of the interior bone.
This is in contrast to osteoporosis, which is diffuse and symmetric.
Signs of hyperparathyroidism on radiography
- Subperiosteal bone erosion
- Distal clavicular resorption (shown)
- Brown tumors (aka osteoclastomas, well circumscribed lytic lesions within bone)
What is happening with this bone?
This is a geographic lytic bone lesion, suggestive of malignancy
What is happening with this bone?
This appearance is described as “moth-eaten”, and is suggestive of numerous tiny lytic lesions within bone, suggestive of aggressive malignancy
What is happening with this bone?
This pattern of erosion is described as “permeative”
Sometimes called “Round cell” lesions for the shape of cells that produce them
Often due to: Ewing’s sarcoma, myeloma, leukemia
What is happening with this bone?
This is multiple myeloma
Note the “punched out” appearance to the skull with very well marginated lytic lesions, as well as the diffuse distribution (not focal like scant metastasis)
What is happening with this bone?
This is osteomyelitis
Note the focal cortical destruction of bone .
Often accompanied by new periosteal bone formation and inflammatory changes (swelling, focal osteoporosis, hyperemia)
Joint space narrowing in osteoarthritis vs rheumatoid arthritis
Rheumatoid: uniform
Osteo: Patchy/nonuniform
In RA, you see subchondral __.
In osteoarthritis, you see subchondral __.
In RA, you see subchondral erosion.
In osteoarthritis, you see subchondral cysts.
Common indications for bone density scans
- Female over age 65
- Male over age 75
- Younger individuals with risk factors:
- Hx of osteoporosis-associated fracture with minor trauma
- Low BMI (<23)
- Premature menopause
- Testosterone deficiency in men
- Chronic glucocorticoid therapy
Causes of osteopenia
Osteoporosis vs osteomalacia (vitamin D related)
DEXA scan t scores
Z score
Takes into account patient demographics
NOT used for DEXA grading (we use the t score, which is basically compared against healthy 20 somethings)
Imaging in osteomyelitis
Start with a plain radiograph
If this is negative but there is still clinical suspicion, or if more information is required, MRI is indicated
Timing of findings in osteomyelitis plain radiography
-
After 3-5 days, early signs become visible:
- Focal loss of the white cortical line
- Subchondral lucency
- Periosteal retraction (fluffy calcification next to cortex)
-
After 2-3 weeks, late signs become visible:
- Periosteal elevation
- Cortical/medullary lucency
Differentiating osteomyelitis from Charcot joint
Done via nuclear medicine by comparing a 3-phase bone scan plus a WBC scan
3-phase bone scan should be positive in both, but WBV scan will be positive in osteomyelitis but negative in Charcot joint.
When is vertebroplasty indicated?
- Spinal fracture with poor alignment
- Spinal fracture with neural impingement
- Failure of conservative management
- Uncontrolled pain leading to hospitalization or inability to tolerate pain medications
- Inability to tolerate bed rest (high risk for DVT, decubitus ulcer, permanent incapacitation)
- Respiratory compromise due to thoracic back pain (in case of thoracic vertebra)
Posterior shoulder dislocation
Note the “lightbulb sign”
CT in MSK imaging
Best at looking at the cortex and for calcifications
Allows you to localize in 3d, unlike x-ray
Also excellent for detecting air in soft tissue
What is the difference in how coronal, saggittal, and axial images are acquired on CT and MRI?
In CT, if you take an axial you can reconstruct saggittal and coronal
On MRI, you need to do all views individually, so it takes 3x as long!
Utility of bone scintigraphy
Tells you where bone mets are
Infective osteitis vs osteomyelitis
Infetive osteitis is infection of just the bone cortex
If the marrow is involved, it is osteomyelitis
Loss of cortical white line
Suggestive of bone destructive process, potentially osteomyelitis
May have a mottled appearance if there is air produced by the infection
Managing suspected septic arthritis
- Arthrotcentesis with gram stain/culture for dx
- Surgical debridement and drainage of the joint to clear infection and prevent sepsis/joint destruction
Calcific tendinitis
Deposition of hydroxyapatite in tendons/bursae
If you see an osteophyte, . . .
. . . there is 100% osteoarthritis
There may be more going on, but the patient also has osteoarthritis
Osteoarthritis joint space narrowing is ___
Rheumatoid arthritis joint space narrowing is ___
Osteoarthritis joint space narrowing is asymmetric
Rheumatoid arthritis joint space narrowing is symmetric
Rheumatoid arthritis leading to osteoarthritis
RA can destroy the cartilage, leading to formation of osteophytes and development of osteoarthritis!
Types of osteonecrosis
Just involving bone marrow: Bone infarct
Involving cortical bone and extending to joint space: Avascular necrosis
Most common primary bone tumor
Multiple myeloma
