radiology 2a

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radiology 2a
2013-02-23 16:34:09

spring 2013
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  1. 5 key things MRIs are good at
    • high contrast resolutino
    • soft tissue (tendon and ligament) detail and pathology -- better than CT
    • can detect occutlt fractures not seen on radiographs or CT
    • abnormal edema or fluid
    • structural abnormalities (gaps, discontinuity in tendons and ligs)
  2. main skill of CTs
    • high spatial resolution (can differentiate things close together, find tiny lesions)
    • better at this than both MRI and x-ray
  3. MRI standard planes
    planes for shoulder MRI
    obtain 3 planes: typically axial, sagital, and coronal

    • BUT for shoulder to optimize detection of rotator cuff tears get
    • coronal oblique (parallel to long aspect of supraspinatus),
    • sagital oblique (perpendicular to long axis of supraspinatus),
    • axial
  4. fat and fluid in T1
    fat is bright, fluid is dark
  5. fat and fluid in T2
    fat is bright, fluid is bright
  6. fat sat T2 aka STIR, how's the fat and fluid
    fat is dark, fluid is bright (reverse of T1)
  7. 8 things on your mental checklist when you're reading an x-ray
    • ID normal bones
    • look for cortical continuity
    • look at alignment
    • look for extra densities or lucencies within or outside bone
    • look at soft tissues (for swelling or effusions)
    • look at adjacent joints
    • compare with prior studies if there are any
    • if there's still concern, consider ordering CT or MRI
  8. 3 arcs to look for in a hand x-ray
    arc I: proximal articular surface of scaphoid, lunate, triquetrium
  9. carpals
    • scaphoid lunate triquetrium pisiform
    • trapezium trapezoid capitate hamate
  10. arc II in the hand x-ray
    distal articular surface of scaphoid, lunate, triquetrium
  11. arc III in hand x-ray
    proximal articular surface of capitate & hamate
  12. how does hook of hamate look in an x-ray?
    it's a circle inf to the 4th + 5th fingers, denser around the boarder of the circle
  13. hand x-ray lateral view, what 4 bones should line up?
    radius, lunate, capitate, third metacarpal
  14. 6 signs of fractures on a radiograph (starred slide)
    • cortical discontinuity or deformity
    • radiolucent fracture lines
    • abnormally white or dense areas representing overlapping bony fragments or impaction of bone
    • extra or unexplained fragments of bone
    • soft tissue swelling / joint effusions
    • callus formationin healing fracture
  15. gamekeeper's thumb aka rabbit hunter's thumb aka skier's thumb
    • disruption of UCL of first MCP joint
    • (the UCL holds the metacarpal to the first phalanx on the ulnar side)
  16. Stener lesion
    displacement of UCL superficial to aponeurosis of adductor pollicis
  17. mallet finger is due to what coming unattached?
    • avulsion of the lateral slips of the extensor digitorum
    • leads to extension of the DIP
  18. There's a high rate of AVN w scaphoid fracture. Why?
    blood supply to scaphoid begins distally and runs proximally, so the prox pole can get AVN

    (if high clinical supsicion of fracture (trauma w pain over snuff box) wrist should be cased and MRI or repeat x-rays taken in a week)
  19. anterior elbow x-ray
  20. lateral elbow x-ray
  21. fat pad sign in elbow
    • darkness surrounding joint (radiolucency ant and/or post) on a lateral radiograph of elbow bent 90 degrees
    • the ant fat paid is normally seen as a faint line that is more radiolucent than adjoacent muscle and is parallel to the anterior distal humerus. Posterior fat pad is normally pressed into the deep olecranon fossa by the triceps tendon and anconeus muscle is invisible
    • suggesting an occult fx and effusion
  22. how can you id olecranon bursitis in an x-ray?
    lateral view x-ray will show massive soft tissue swelling post/inf to olecranon
  23. essex lopresti fracture-dislocation
    fracure of radial head + dislocation of radio-ulnar joint (interosseous membrane disruption)
  24. monteggia fracture/dislocation
    • fracure of ulna and dilocation of prox radius (nightstick fracture)
    • if dislocation is missed can lead to AVN
    • Galeazi = fx of radius and dislocation of distal ulna (less common)
  25. Y-scapula x-ray thing
    • it's a side view, where the acromion is to the left, the coracoid is to the right, and the bottom of the scap contributes to make a Y
    • the humeral head should sit right in the center. If it is shifted toward acromion or coracoid you know it's post or ant dislocation
  26. axillary view of GH joint
    the corocoid looks high with the acromion low, and you can tell if it's ant/post dislocation based on where the head is rel. to those two
  27. Hill Sachs lesion
    fx of sup-lat hum head from collision w glenoid rim when hum is dislocated ant

    • supero-lateral aspect of humeral head
    • best seen in AP internal rotation plain film
  28. bankart lesion
    • inferior aspect of glenoid labrum is injured due to repeated ant shoulder dislocations
    • may req. CT to visualize
  29. for which bones would you typically get just 2 views of x-rays?
    • long bones (arm, leg, forearm, calf)
    • get 2 orthoganal views (90 degrees to each other)
    • AVP + lat
  30. x-rays, when would you typically get 3 views: AP, lat, oblique
    joints - wrist, hand foot, ankle, elbow, knee
  31. what 3 x-rays to typically get for trauma to shoulder
    • AP
    • Y-scap
    • axillary
  32. what 2 x-rays to typicaly get for non-traumatic shouulder
    AP views in IR & ER
  33. typical pelvis & hips 2 x-ray views?
    • AP
    • frog-leg lateral view
  34. if lunate is pushed anteriorly and angulated volarly (as in one of the slides) it can impinge on what nerve?
  35. what's happening in a "perilunate dislocation" (one of his slides)
    the lunate stays with the radius while the rest of the carpals sublux dorsally & proximally
  36. AP view of shoulder, how to know if the hum is IR or ER
    • in ER you can see the crest of the greater tub on the lateral side of the hum head
    • in IR the head just looks round
  37. in posterior dislocation of shoulder, what motion goes with the post mvmnt?
  38. what usually causes posterior dislocation (w/IR) of shoulder?
    convulsions, not trauma
  39. what hits when in post dislocation of humeral head?
    ant head -- post glenoid fossa
  40. why is it hard to diagnose post dislocation of hum head on x-ray?
    can mimic adhesive capsulitis or frozen shoulder ... need to get a CT or MRI to check
  41. what percent of shoulder dislocations are ant? post? inf/luxatio?
    • ant: 95-97%
    • post: 2-4%
    • luxatio/inf: 0.5%