MSK US Flashcards
Skin & subcutaneous tissue
- high freq* linear probe
- only need a shallow depth of penetration & high detail
- use B-mode & Colour Doppler
- watch yr probe pressure
- use a good layer of gel or a water bath (glove filled w water)
Abscess formation
- often starts w separation of fatty areas, like cellulitis
- maybe be hypoechoic but may not be
- will have increased vascularisation with time
- May swirl or appear to move in increased fluid, but not always if more solid contents
Benign masses US
- anechoic - true cyst is benign
- thin walled
- well defined
- wider than tall
- a vascular/minimally vascular
- hyperechoic non-shadowing
- does not cross tissue layers
Benign soft tissue masses
- well defined
- avascular
- variable echogenicity from hypo/hyper or mixed
- rare to be in muscle
Epithelial inclusion/sebaceous cyst
- sebaceous cells push into deeper layers
- typically not anechoic
- may have edge shadowing
- may be at varied depths
- Check: sinus, leaking and adjacent structures
Pilonidal cyst
- abscess
- sinus
- hair
- often hypoechoic compared to surrounding
- white evidence of hair within cyst
- can be quite large so ensure U define its entire extension under the skin
Malignant masses US
- cannot diagnose precisely from ultrasound alone
Suggestive if:
- large
- not from synovial space (bursa or tendon sheath)
- hyperechoic & hypervascular
- Ill-define & solid
- posterior shadowing
- invading tissue planes/destructive (very suspicious!!)
- thick walled
Vascular subcut* masses
Haemangiomas
Arteriovenous malformations
Bone shaft & Joints
- highest freq* probe possible
- excellent for joints, not so great for bone shafts (except for stress #s)
- scan in two planes: if u can’t see it in both planes, it’s not real
- use colour to ensure it’s not a nutrient channel
- lots of gel/stand off pad/bath
- move & stress joints: to get movement to move fluid/items to show things better
- be aware of heating: esp in smaller places (esp hands)
- talk to the Pt, esp when looking for stress #s, they’ll be quite tender & a Pt’s response shows if neurological Vs MSK
Normal adult bone Appearance
- echogenic
- linear
- reverberation artifacts: mirror images
- nutrient channels present: vessels going thru periosteum
Normal child bone Appearance
- echogenic
- linear
- reverb* artifacts
- periosteum
- Sharpeys fibres - thicker cortical bone layer (creates hypo echoic line on cortical surface.
Normal Adult joint appear*
- echogenic
- reverb* artifact
- articulate/hyaline cartilage: hypoechoic layer between joint capsule & bone
- joint capsule
Normal child joint Appear*
- echogenic
- growth plate/physis
- reverb* artifact
- articular/hyaline cartilage: thicker than Adults, still quite dark (not joint effusions, compare to collateral side!!)
Abnormal bone appearance
Fractures:
- stress #s in kids - bone bruising (bony bruising, wider sharpeys fibres, along the cortex)
- trauma
- pathological
Adult #s:
- step deformity & adjacent soft tissue inflammation/haematoma
Aged #s:
- loss of normal tissue planes & raised cortical surface with healing
Shoulders:
- # humeral head may be found, not just a torn tendon!
Pubic symphysis:
- erosive changes possible
- bowing out of the joint capsule indicates underlying changes
Pathological #s:
- normal cortical margin that gets lost
- adjacent soft tissue mass, normal tissue planes have been disrupted
- cloud like appearances around bone
- loss of smooth cortical surfaces
Exostosis:
- benign, bony outgrowth if cartilaginous tissue
- bursitis around bony outgrowth
Abnormal joint appearance
Traumatic:
- simple effusion: twisted knee
- complex effusion: rheumatoid/septic arthritis
- can be hypoechoic or echogenic region
Infective: septic Arthritis
Degenerative:
- erosions: deterioration in cortical surface, fluid & swelling around joint region
- osteophytes: loss of smoothness of bone surface, loss of volume of joint space,
Vascularity:
- bowing out of joint capsules
- colour: vasc*
- no colour: synovial hypertrophy
Cartilage:
- articular: hard cartilage, graded changes, 0-3 (often involves osteophyte formation: grades 0-3)
- fibrocartilage: spongy cart*, meniscus can protrude w trauma/degenerative changes (MRI better at detecting)
