Dr Dave McCreary Emergency Physician
Peer review: Dr Stephen Gilmartin
Welcome to Fast Fridays – a case-based, rapid review of a topic. The cases have been adapted from real patients but have been changed for anonymity and to emphasise key learning points.
A 60-year-old gentleman presents for assessment of a 2-week history of a swollen, erythematous left foot. His GP has been treating him for cellulitis with oral flucloxacillin, which has offered no improvement. He has a previous medical history of poorly-controlled type two diabetes with associated nephropathy and peripheral neuropathy. On assessment, he is afebrile, with normal observations and walked unaided from the waiting room for his assessment. The patient’s left foot is swollen compared to the right, is warm to touch, has no tracking redness, no skin breaches and looks like this:
Image courtesy of the BMJ(1)
What are your differentials for this presentation?
- Non-resolving cellulitis
- Foreign body
- Charcot foot
What is your interpretation of this X-ray?
What would your disposition be for this patient?
🥱 that’s not a very bloggable case, Dave…
One week later, the patient was referred back to the orthopaedic team by his podiatrist with the following X-ray:
Clearly no longer 'normal'; what's your interpretation of the X-ray this time?
So, What's the diagnosis?
What is Charcot foot?
What's the pathophysiology?
- Neurovascular theory:
- Nerve damage → increased local vascularity → osteoclastic activation → osteopenia, fractures, deformity
- Neurotraumatic theory:
- Microtrauma to insensate joints → progressive bony destruction → repeated partial healing & activation of pro-inflammatory junk cytokines → increased vascularity → osteoclasts again as above
- They reckon hyperglycaemia makes it worse too (increased advanced glycosylation end products, if you’re interested), so it’s more common in poorly controlled diabetics.
- Inflammatory (as in this case)
- Bit of warmth, swelling, redness ± pain
- Radiographically normal
- MRI helpful
- Joint and bone destruction
- Joint unstable
- Destructive phase slows, healing starts
- Bones and joints healed
- Residual instability and deformity may occur
How is it diagnosed?
It’s largely about pattern recognition (as with so many things in medicine). Think of it in any Diabetic patient presenting with swelling, redness and (sometimes) pain in the foot and ankle of short duration (within 4-6 weeks of symptoms)(2).
Probably not helpful in the early stages as can be normal, but they can help include or exclude the differentials
Imaging? The cruncher for this case.
- Plain films are often normal in the early stage and should not exclude Charcot foot
- MRI is the best option for detection of subtle, early changes and also has great sensitivity and specificity for osteomyelitis
- CT is better than plain film for osteomyelitis, but not reliable in early disease
How is it managed?
- Any suspected Charcot foot should be made immediately Non-Weight-Bearing and referred to orthotics for a Total Contact Cast (TCC).
- Off-loading can arrest disease progression by disrupting the inflammatory cycles mentioned above
- In the meantime, they can have a double tubigrip for swelling and pain.
- Urgent outpatient referral to podiatry, orthotics, and endocrinology to get their diabetes in order.
🔭 The Retrospectoscope – was that first X-ray really normal? 🔭
Let’s look at the AP view and, as I often like to do, let’s see what my Orthoflow App would say…
Images courtesy of Orthoflow
When assessing for midfoot injury we look (amongst other things) for disruption of the 1st metatarsal-medial cuneiform line, then for disruption of the 2nd metatarsal-middle cuneiform line. Disruption of these lines suggests disruption of the Lisfranc ligament.
I would suggest there is definitely a disruption in both of those lines in this case. If you were in any doubt, weight-bearing views may help or imaging of the unaffected foot will provide comparison.
🤓 Learning Points 🤓
- Not all reddness is cellulitis.
- Consider an exclude alternative diagnoses.
- Keep a high index of suspicion for Charcot foot in patients with peripheral neuropathy and diabetes in particular.
- Plain films aren’t helpful in the early stages of Charcot foot.
- If it’s at all a possibility, treat as Charcot foot, NWB the patient, consider advanced imaging and seek a podiatry/orthopaedic opinion.
He dislikes coriander, decaf coffee (“really, what’s the point?”) and dermatology.