A Hot Red Foot With a Negative X-ray

Differential, in order of urgency

1. Acute Charcot neuroarthropathy - the leading candidate. Unilateral warmth (a 3.5 °C difference is well past the ~2 °C threshold), erythema, and edema in a long-standing neuropathic foot, with a sudden change in shoe fit, is the classic presentation. The foot is red and hot without an ulcer or portal of entry.
2. Cellulitis - plausible but weaker: temperature is 37.1 °C and WBC is normal. Cellulitis of this apparent severity would usually show systemic signs, and there is no wound on that foot to serve as a source.
3. Deep infection/osteomyelitis - keep on the list. Probe-to-bone is negative, which lowers but does not exclude it; the test has good positive predictive value and poor negative predictive value.
4. DVT - unilateral swelling, less likely to produce this degree of calor, but not excludable clinically.

Next 24 hours

• Urgent podiatry/orthopedic and vascular referral. Charcot is a time-critical diagnosis; delay causes rocker-bottom deformity and amputation.
• Do not accept the 10-day-old X-ray as the answer. Early Charcot films are frequently normal. Request repeat imaging or, better, MRI.
• Do not reflexively start antibiotics. With a normal WBC, no fever, and no wound on the affected foot, antibiotics treat the wrong problem and delay the right one. If the picture is genuinely ambiguous, obtain imaging and cultures and let the team decide.
• Take the weight off the foot now - non-weight-bearing, immobilize, and elevate as ordered.
• Check the other foot, both pulses, and skin temperature again as a baseline for comparison.

What the evidence supports in principle: an irremovable knee-high total contact cast is first-line for a plantar neuropathic ulcer at the metatarsal head when there is no contraindication, because it is the only device that reliably enforces adherence.

Why this patient is not a TCC candidate today

• Possible active infection or acute Charcot in the same limb. Active infection and osteomyelitis are standard contraindications to casting - a cast over an unrecognized infection is a route to limb loss.
• Documented nonadherence (walking barefoot "to let it breathe") makes an irremovable device a poor fit until that behavior is addressed and understood.
• Uncontrolled edema and an unresolved differential mean the limb is still changing, and a cast made today may be wrong within days.

Plan

1. Immediate: strict non-weight-bearing on the left; a removable knee-high walker with a rigid rocker sole for transfers, with the foot enclosed at all times - including in bed and at night.
2. Resolve the diagnosis first (imaging and specialist input). Once infection and acute Charcot are excluded or controlled, convert to an irremovable device or a Charcot restraint orthotic walker as the deformity is defined.
3. Add a total-contact insole and accommodative footwear for the contralateral foot - the contralateral limb is at high risk and is currently unprotected.
4. Recheck the device at every visit for fit, rubbing, and skin integrity under the edges.

Adherence is the active ingredient. A walker he takes off is worth less than a cast he cannot remove - but only once the limb is safe to cast.

1. 'Barefoot at home' is the single most damaging behavior here. He believes air is therapeutic; explain that a neuropathic foot cannot feel injury, so the floor is a source of wounds, not a treatment. Concrete rule: no weight on the foot without the boot, including nighttime bathroom trips. Ask what makes the boot hard to keep on (heat, fit, habit) and solve that specifically - a rule without a workaround fails.

2. Daily foot inspection with a mirror, and temperature checking. Teach him to look at the sole and between the toes, and to feel both feet for warmth difference. Given the current 3.5 °C asymmetry, he needs to understand that heat and swelling mean "call today," not "wait and see."

3. Glucose control reframed as wound care. A1c 10.4% is not a background number - hyperglycemia impairs collagen synthesis, neutrophil function, and perfusion, and it is the reason his 2 cm ulcer is not closing. Coordinate with his diabetes team rather than delivering a lecture at a wound visit.

Also cover, but as reinforcement rather than lead messages: shoe fit and when to be measured (feet change with neuropathy and deformity), the reason his shoe suddenly stopped fitting, and who to call - with a name and number.

Teach-back: have him show you how he will check his foot tonight and state the rule for the boot. If he cannot, the visit is not finished.