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
  • Osteomyelitis
  • Charcot foot
  • Gout
  • DVT
The following X-ray was taken:
What is your interpretation of this X-ray?
The X-ray was interpreted in the department and formally reported as normal.
What would your disposition be for this patient?
As the patient reported that the erythema was improving, he was discharged to continue the flucloxacillin his GP has prescribed and follow up with his podiatrist.
🥱  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?
“Homolateral Lisfranc’s dislocation. Widening of the joint spaces between the cuneiforms and also the cuneiform-cuboid articulation, with medial subluxation of the medial cuneiform, lateral subluxation of the lateral cuneiform.”
So, What's the diagnosis?
This was Charcot foot all along.

What is Charcot foot?
A non-infectious destruction of bone and joint associated with neuropathy and characterised by inflammation in the earliest phase. It was classically described by Jean-Martin Charcot (Off-of all things Charcot – he really did love to stick his name on things) in 1883. It can be caused by any condition resulting in loss of protective sensory innervation or autonomic neuropathy.  Think diabetes, alcohol, spinal injury etc.
What's the pathophysiology?
There are a couple of theories as to what is going on here:

  • 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.
Stages
  1. Inflammatory (as in this case)
  • Bit of warmth, swelling, redness ± pain
  • Radiographically normal
  • MRI helpful
  1. Developmental
  • Joint and bone destruction
  • Joint unstable
  1. Coalescence
  • Destructive phase slows, healing starts
  1. Remodelling
  • 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).

Bloods?

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.

References and Further Reading:

  1. Baglioni P, Malik M, Okosieme OE. Acute Charcot foot. Bmj. 2012;344(mar14 1):e1397. Doi: 1136/bmj.e1397
  2. Yousaf S, Dawe EJC, Saleh A, Gill IR, Wee A. The acute Charcot foot in diabetics. EFORT Open Rev. 2018;3(10):568–73. Doi: 1302/2058-5241.3.180003

Dave McCreary

Dave McCreary

Emergency Physician

Dave is an Emergency Physician and project lead for our FOAMed content. He completed training between the UK and Australia and completed an MSc in Trauma Science with QMUL. His clinical interests include trauma, critical care, orthopaedics, evidence-based medicine and human factors. Dave is a regular contributor the RCEMLearning podcast with a regular evidence-based medicine segment “New in EM” and is a FOAMed editor for RCEMLearning.

He dislikes coriander, decaf coffee (“really, what’s the point?”) and dermatology.