Clinical Case 121: Supracondylar Sono Subtlety

Another quick case from the Paeds files…

Simple story – 5 year old boy playing with his 6 year old sister on bunk beds.  Mum heard a thud then a scream and found him on the floor – he has fallen about 1 metre onto his outstretched arm.  No other injury seen.

On arrival to the ED he is holding his arm by his side in 90 degrees flexion, when asked – he points to his antecubital fossa to show where he is sore.

He has good pulses distally, there is some localised swelling but no deformity of the elbow.

So what is going on?  Well as usual it is 3 AM and there is no Xray available…  but as I said at SMACC Chicago: “No Xray, No Problem.”

So lets pull out the US machine and have a gander:

First view is a transverse of the posterior humeral condyles and fat pad.  The is abnormal – usually the fat pad lies beneath a line, convex down between the condyles – this pad is billowing up – this is a sonographic “sail sign” the tell tale for an elbow haemarthrosis.posterior fat pad

The second image is a long view of the posterior humerus with triceps tendon overlying.  There is  a subtle cortical break evident (can you see it?)  These can be tricky as they look a lot like normal growth plates in little kids – so luckily he has 2 arms and we can scan the other one to compare.  Asymmetry suggests a fracture – you can also use the probe to illicit tenderness to check fracture vs. growth plate.triceps

The third image is a long view of the proximal radius – checking for a fracture of the radial head – this was normal.  The other side looked the same and there was no tenderness over the radial neck.  The elbow was enlocated on further scanning.radial head

So we have a good story for a supracondylar fracture, a definite haemarthrosis, a subtle crack in the distal humerus and a normal looking radial head/neck.

So he got a long arm plaster and returned for review and an Xray to be sure…

Here are the plain film images:

So the subtle signs are seen – but I reckon they are more obvious on the US. What do you think?supra latsuprAP?

So a few controversial questions….

(1) Do we really need to Xray this kid?  It is a subtle undisplayed fracture which will always be managed conservatively.

(2) If the plain film had been reported as “Normal” or “non-diagnostic” what would you do given these US images?

Let me know your thoughts

And go check out the Sonowars podcast from Mike & Matt over at USPodcast for a more in depth look at how to do this scan. Fast forward tot he 20 minute mark for “fat pad sign”

And here is the 2012 paper by Rabiner et al [Crit US Journal ] that showed a 98% sensitivity for detecting elbow fractures.  The specificity was only 70%, against Xray as a god standard.  So beware of overcalling these?





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