Summary

Charcot Neuroarthropathy (CN) is a progressive, destructive, non-infectious arthritis associated with loss of sensory innervation (neuropathy). It most commonly affects the midfoot of diabetic patients. The condition begins with an acute inflammatory phase (Active Charcot) characterised by a red, hot, swollen foot, often triggered by minor trauma. This unregulated inflammation leads to aggressive osteolysis (bone soaking away), fractures, and joint dislocation. If weight-bearing continues during this phase, the foot collapses into a "Rocker Bottom" deformity. Management relies on early recognition and immediate offloading (Total Contact Cast) to arrest bone destruction and preserve architecture. Surgery is reserved for chronic deformities causing unmanageable ulcers.

Key Facts

• Target Group: Diabetics with dense neuropathy (>10 years disease).
• Trigger: Minor trauma (sprain/trip) in a numb foot.
• Sign: Temperature difference >2°C compared to the contralateral foot.
• Misdiagnosis: Often treated as "Cellulitis" or "Gout" for weeks. This delay is catastrophic.
• Deformity: Midfoot collapse (Lisfranc joint) -> Rocker Bottom Foot.
• Treatment: TOTAL CONTACT CAST (TCC) until the "fire goes out" (temperature normalises).

Clinical Pearls

"It's not Infection": If a diabetic presents with a red, hot, swollen foot but has NO PORT OF ENTRY (no ulcer, no cut) and is SYSTEMICALLY WELL (normal WCC/CRP), it is Charcot, not Cellulitis. Elevate the leg for 5 mins - Charcot redness fades (dependent rubor); Cellulitis redness stays.

"The Painless Fracture": Patients often present walking on a foot with multiple fractures and dislocations because they simply cannot feel it. "I just noticed my foot changed shape."

"The Race Against Gravity": Once the midfoot collapses (arch reverses), the cuboid/navicular become the lowest point of the foot. The skin here cannot take weight. It ulcerates -> Osteomyelitis -> Amputation. We treat Charcot to prevent the Ulcer.

The natural history of Charcot follows a predictable cycle.

          RED HOT DIABETIC FOOT
                   ↓
      IS THERE AN ULCER / ENTRY POINT?
       │                    │
      YES                   NO
       │                    │
    INFECTION?         CHARCOT?
    (Check CRP)       (Check Temp Diff)
       ↓                    ↓
    ANTIBIOTICS        IMMEDIATE OFFLOADING
    + IMAGING          (Total Contact Cast)
                            ↓
                    SERIAL X-RAYS / TEMP
                    (Weekly/Biweekly)
                            ↓
                    Wait for Quiescence
                    (Stage II/III)
                            ↓
                    CUSTOM FOOTWEAR (CROW)
                            ↓
                    If Ulcer/Unstable
                            ↓
                    RECONSTRUCTION SURGERY

1. Offloading (The Non-Negotiable)

• Goal: Stop the bone crumbling while it is soft. Convert a "fluid" situation into a stable fusion.
• Gold Standard: Total Contact Cast (TCC).
  • A fibreglass cast moulded intimately to the leg.
  • Ideally non-weight bearing (crutches/wheelchair).
  • Changed weekly (as swelling reduces, cast becomes loose).
• Duration: Typically 4-9 months. Until temperature is within 1°C of contralateral side and X-rays show consolidation.
• Compliance: The hardest part. TCC forces compliance because the patient cannot remove it.

2. Medical Therapy

• Bisphosphonates (Pamidronate/Zoledronate):
  • Inhibit osteoclasts.
  • Evidence is mixed. May reduce temperature quicker but does not provenly change deformity outcomes. Used by some specialists.

Surgery is NOT done in the acute inflammatory phase (Stage I) – "Operating on Charcot in the active phase is like operating on cheese". Hardware will fail. Surgery is reserved for Stage III (Chronic) if deformity is unmanageable.

Indications

1. Recurrent Ulceration: Despite custom shoes, the bony lump causes ulcers.
2. Unbraceable Deformity: Foot so twisted it won't fit in a shoe.
3. Severe Instability.

Procedures

1. Exostectomy:
   • Simply shaving off the bony prominence (e.g., plantar cuboid).
   • Simple, low risk.
2. Arthrodesis (Fusion):
   • Realigning the arch and fusing the joints.
   • Superconstructs: Because the bone is poor quality, we use "Superconstructs":
     • Fusion beyond the zone of injury.
     • strongest implants (locking plates, beams).
     • Intramedullary beaming (bolts down the metatarsals).

Charcot can hit different zones (Sanders & Frykberg):

• Zone I (Forefoot): MTPJs / IPs. (15%). Good prognosis.
• Zone II (Midfoot): Lisfranc / Chopart joints (40%). Most common. High risk of Rocker Bottom.
• Zone III (Hindfoot): Subtalar / Calcaneus (30%). High instability. Varus/Valgus tilt. Hard to brace.
• Zone IV (Ankle): (10%). Disastrous. Often needs amputation.
• Zone V (Calcaneus): Avulsion fracture of Achilles.

Key Guidelines

1. NICE NG19: Recommend MRI if X-ray normal but Charcot suspected. TCC as first line.
2. IWGDF: Guidelines on Charcot.

Prognosis

• Once Charcot develops in one foot, the other foot is at high risk.
• If deformity is prevented (early casting), prognosis is fair.
• If Rocker Bottom develops -> Ulcer risk -> Amputation risk.

What is Charcot Foot?

Charcot (pronounced "Shark-oh") is a condition that affects the bones and joints in people who have lost feeling in their feet (neuropathy). Because you can't feel pain, you might twist your foot or walk on it too hard without knowing. This triggers a huge inflammation reaction. The bones become soft and can break or crumble.

Why is my foot hot?

The heat comes from the inflammation and increased blood flow trying to heal the damage. It is the most important sign.

Why do I need a cast?

Your bones are currently soft, like wet cement. If you walk on them, your foot will collapse and change shape permanently (Rocker Bottom). The cast holds the foot in the perfect shape while the bones harden again. This takes months, but it saves your foot from amputation later.

Can it be fixed with surgery?

Usually, we wait until the "fire is out" (the inflammation settles). We prefer to treat with casts and special shoes. Surgery involves major reconstruction with bolts and plates and is only done if necessary.