Trauma | SA/NT SAQ 2020.2 Q4

Brain Food is a project to drip feed clinical knowledge (in the form of mock SAQs) to satisfy those hungry neurons. Sources are SA/NT Trial Exam 2020.2 and Monash 2022.1. Answers are prone to ageing. Leave a comment if you don't understand or something doesn't seem right...
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PS we don't use the mock questions uploaded to ACEMs official mock

A 64 year old carpenter presents to your emergency department four days after an injury to the palmar aspect of his hand while he was repairing a window frame.

There is minimal swelling. You suspect there might be a retained foreign body and decide to use ultrasound to examine his hand.

1. What type of transducer would you use? (1 mark)

HF linear probe
Freq range > 12MHz

2. List three (3) parameters on the US machine you would adjust to optimise images. (3 marks)

MSK or soft tissue pre-set
Depth
Focus
​TGC or gain 

3. List four (4) advantages and four (4) disadvantages of ultrasound guided foreign body removal in ED. (8 marks)

Advantages: 

1. No radiation
2. Able to visualise location and assess size of FB: assess depth, plan procedure approach
3. Able to visualise adjacent structures (e.g. neurovascular) to assess injury and avoid inadvertent injury while attempt at removal
4. Possible to visualise non radio-opaque FB on USS (e.g. wood, plastic, glass)
5. Able to remove USS in real time to guide removal of FB and confirm 
6. Able to assess immediate post procedural complication associated with FB (e.g. granulation tissue formation, collections)

Disadvantages: 

1. Operator dependent: technique, choice of transducer, level of experience etc. 
2. Best time window: 24 hours post retained FB, late presentation with increased inflammation, scarring, induration makes visualisation of FB and removal of FB under USS guidance more difficult with more complications
3. Once skin incised, air may prevent visualisation
4. Visualisation depends on level of echogenicity of FB
5. Calcification in soft tissues may look like FB
6. Factors obscuring FB: large overlying haematoma, subcutaneous emphysema
7. Inability to obtain transducer contact (e.g. large laceration)
8. Ultrasound artefacts that may obscure FB 
9. Artefact from forceps.