It’s a wonderful rag-bag term, ‘scan’. Both a noun and a verb, it’s somehow become interchangeable with the word ‘diagnostic’, and each year, some new miracle machine is invented.
My Mother’s bloodhound’s nose is an excellent scanner.
It’s swiftly able to detect the alluring waft of a child’s unguarded ice cream from the opposite side of her local park, but as with other mis-uses of ‘scanning’, it can lead to confusion, distress and unnecessary costs (typically around £1.85 to replace the slobbered-on Mr Whippy – no flake).
We can be forgiven for confusion when it comes to deciding on imaging, as there are many variables, and some of them aren’t even clinical.
One of the biggest challenges you may be facing, is not some much which imaging process to use to help with a patient’s diagnostic work-up, but when to go ahead and image.
There are some occasions when you really need to get some imaging done because something really bad might happen if something isn’t spotted and taken care of quickly – e.g. when you suspect cauda equina.
Then there are occasions when something is obviously busted, and you need to be able to confirm it, so that you can plan for a procedure – e.g. a femoral neck fracture.
Other times, might have get an ominous sensation that something ‘dodgy’ might be going on, and you need to swiftly get to the bottom of what’s behind their red flags/antalgic limp/ptosis etc.
Occasionally, you might experience the feeling that time is passing by and the patient’s recovery trajectory is taking a nose-dive, and you need to find what’s holding them back.
And finally, you may need take the patient on a potentially lengthy journey of recovery, and you ‘re looking for ‘diagnostic evidence’ to enable the patient to ‘buy into’ that journey.
Whilst it is true that there is a tendency for clinicians (particularly hospital doctors) to over-utilise diagnostic testing, there may be the odd occasion when we are holding a patient’s progress back by delaying imaging.
So when should we be imaging earlier?
In our MSK world, I think there are few ‘usual suspects’ in the scenario of ‘should have imaged sooner rather than later’.
I’m going to jump up on my soap box (forgive me) and riff a little here on some of my recent imaging experiences.
The initial management of severe ankle sprains:
We’ve all seen patients who finally get round to having an MRI months after their initial injury that they’ve failed to cover from conservatively. They’re told that that they need surgery to repair the syndesmosis /ATFL/CFL tearing, and it’s going to be another six months before they’re back to sport. The unhappy camper situation could have been avoided if the diagnosis was clarified earlier.
How do you know an ankle sprain needs imaging? It might be worth considering the following:
If the patient can fully weight bear and walk comfortably, and they have a negative Ottawa’s screen, then you’ll have ruled out most fractures… or rather the ones that matter initially…
But if they have pain on trying to hop or can’t tip toe or plantar flex, it’s a syndesmosis injury till proven otherwise, so offload them, boot them, and MRI them.
Some fibular injuries like to ‘hide’, and you may have a patient who presents with lateral calf pain or ankle pain, e.g after catching an edge on the ski slopes, or twisting their ankle in high heels. You’ll want to pick up that cheeky little fib fracture that fails to show on x-ray, but shows up nicely on MRI, so have a low threshold for imaging these patients, so you can offload them and get the patient better quickly.
Navicular and fifth metatarsal stress fractures:
These run a risk of non-union, and deserve respect – so if we suspect them, surely it’s our duty to confirm and treat them?X-rays and ultrasound won’t cut it here – so early MRI is key.
Traumatic shoulder labral (or SLAP) tears:
Think of these when your skiers and snowboarders report a juicy wipeout that’s left them with pain on elevating their arm overhead and a positive crank test. Some traumatic labral tears warrant early surgical repair, but you’ll need a 3T MRI to spot one, and imaging done on a 1.5 or 2Tesla scanner won’t be sufficient to rule it out, unless you add in an arthrogram – expensive and invasive. Some talented ultrasonographers may be able to spot a SLAP, but it’s highly operator dependant. MRI will additionally rule out your skier’s undisplaced greater tuberosity fracture – often undetectable on x-ray, and not the injury you want to be tickling up with your favourite rotator cuff theraband exercises.
Pars stress fractures:
Not uncommon in younger tennis players and golfers who have pain into extension and rotation that waxes and wanes according to loading.
Pars symptoms may be confused with facet joint pain, or (dare I say it) ‘bad posture’, and until you’ve pinned it down with an MRI, you and your patient could be going through very protracted rehab process.
The flip side of imaging is that we have to remember there may be side effects or potential risks.
SPECT CT, for instance, is a great imaging tool but it comes with a small radiation tariff. We must also remember that there’s a chance that we get results that aren’t ‘accurate’, as imaging reporting is, afterall, subjective. Are you confident in your ability to be able to differentiate between expected age related or degenerative changes and true ‘pathology’? Do you have a way of further ‘proving’ that your imaging findings are truly your patient’s pain generator, and have you the skills to be able to convey these sometimes complicated concepts to patients? There is nothing worse than the helpless feeling of having ended a consultant with a patient, and leaving them in ‘diagnosis limbo’, because you didn’t know how to act on the findings. In other words, surprises aside, when ordering imaging, you should be thinking of exactly what you’re expecting to confirm or rule out, and know from the outset how it will influence your treatment management decisions.
If you learn to order imaging correctly, and in a timely fashion, you can avoid what may be a potentially costly and even an anxiety inducing process for patients.
This gets them quickly back out on the ski slopes, and you’ll be ready to patch them up again when they return…