Charcot Foot

Aka: Charcot Foot, Charcot Ankle

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II. Epidemiology

  1. Bilateral in 9 to 35%
  2. Age typically over 40 years old
  3. Most common in Diabetes Mellitus with Peripheral Neuropathy
    1. Type I Diabetes patients are younger but with longer standing diabetes at diagnosis of Charcot Foot

III. Pathophysiology

  1. Progressive deterioration of weight bearing joint as a complication of Peripheral Neuropathy
  2. Sites of Neuroarthropathy
    1. Medial tarsometatarsal joint (most common site)
    2. Midfoot involvement accounts for 70% of cases
  3. Theories of pathogenesis in Diabetes Mellitus
    1. Neurotraumatic injury
      1. Repetitive minor Trauma to foot
      2. Loss of proprioception and Pain Sensation
    2. Neurovascular injury
      1. Repetitive minor Trauma to foot
      2. Autonomic vascular reflex
        1. Hyperemia
        2. Periarticular Osteopenia

IV. Risk Factors

  1. Diabetic Neuropathy (Diabetes Mellitus)
    1. Lifetime Prevalence of Neuroarthropathy in Diabetes Mellitus: 0.8 to 7.5%
    2. Lifetime Prevalence of Neuroarthropathy in Diabetes Mellitus with Neuropathy: 29-35%
    3. Associated with poor Diabetes control (Hemoglobin A1C >9) >15 years
  2. Alcoholic Neuropathy
  3. Sensory loss
    1. Cerebral Palsy
    2. Leprosy
    3. Congenital insensitivity to pain
  4. Other contributing factors
    1. Obesity
    2. Chemotherapy
    3. Trauma
    4. Iron Deficiency Anemia
    5. Rheumatoid Arthritis
  5. Other markers of significant Diabetic Neuropathy
    1. Foot Ulceration
    2. Retinopathy
    3. Nephropathy, Renal Failure or Renal Transplantation

V. Types

  1. Atrophic Neuroarthropathy
    1. Localized to forefoot
    2. Osteolysis of Metatarsal heads
  2. Hypertrophic Neuroarthropathy
    1. Affects midfoot, rearfoot and ankle)
    2. Sanders and Frykberg System (anatomical classification 1 to 5)
    3. Eichenholtz Classification (clinical and radiographic criteria)
      1. Stage 0: Clinical (acute inflammatory)
        1. Erythema, edema, and warm foot
        2. No fever or skin break, normal XRay, normal CBC
        3. Often associated with minor Trauma History
        4. Early diagnosis critical to prevent progression
      2. Stage 1 Fragmentation (Acute Charcot)
        1. Periarticular Fractures and joint dislocations
        2. Unstable and deformed foot
      3. Stage 2 Coalescence (Subacute Charcot)
        1. Bone debris resorbed
      4. Stage 3 Reparative (Chronic Charcot)
        1. Fragments fuse, resulting in re-stabilization
        2. Stable, but deformed foot

VI. Findings: Presentation

  1. Peripheral Neuropathy (esp Diabetes Mellitus) and Obesity in age over 40 years old AND
  2. Unilateral swollen limb
  3. Loss of plantar arch
  4. Minimal pain
    1. Painless in up to half of patients
  5. Low mechanism injury (e.g. minor overuse or sprain)
    1. No known preceding Trauma in up to half of patients

VII. Signs

  1. Warm, swollen, erythematous lower extremity (esp. over affected joints)
    1. Erythema improves with elevation above heart level for 5-10 min (distinguish from infection)
  2. Normal features that distinguish from other diagnoses
    1. No fever
    2. No open wound (unless complicated by Skin Ulcers)
    3. Normal pulses

VIII. Diagnosis

  1. Identify Peripheral Neuropathy
    1. Loss of Achilles Reflex
    2. Monofilament Foot Sensation Test abnormal (poor Test Sensitivity)
  2. Differentiate Osteomyelitis
    1. See Suspected Osteomyelitis in Diabetes Mellitus
    2. Probe To Bone Test (Described in Osteomyelitis)
  3. Brodsky Test
    1. Differentiates Charcot Stage 0 from Cellulitis
    2. Technique
      1. Patient supine with involved leg raised 10 minutes
    3. Interpretation
      1. Charcot Process: Swelling and erythema dissipate
      2. Infection: Swelling and erythema persist

IX. Differential Diagnosis

  1. Infectious conditions
    1. Cellulitis or Erysipelas
    2. Osteomyelitis
    3. Septic Arthritis
  2. Rheumatologic Conditions
    1. Gout
    2. Pseudogout
    3. Rheumatoid Arthritis
    4. Acute monoarthropathy
  3. Musculoskeletal conditions
    1. Plantar Fasciitis
    2. Ankle Sprain
    3. Foot Fracture
    4. Tumor
  4. Vascular conditions
    1. Deep Vein Thrombosis
    2. Venous Insufficiency

X. Labs

  1. Consider labs obtained in Osteomyelitis
  2. Normal labs that distinguish from other diagnoses
    1. Normal Complete Blood Count
    2. Normal acute phase reactants (C-RP, ESR) unless infection (e.g. Osteomyelitis)

XI. Imaging: Foot XRay

  1. Precautions
    1. Bony destruction may not be visible on xray for 6-12 months
  2. Comparison bilateral weight bearing XRays
    1. Evaluate for instability
      1. May appear as ligamentous avulsion Fractures (small avulsed bone fragments)
    2. Evaluate for Osteomyelitis
  3. Atrophic Neuroarthropathy (esp. midfoot)
    1. Metatarsal heads have pencil point appearance
    2. Midfoot Fractures are often missed
  4. Consider additional testing for Osteomyelitis
    1. See Suspected Osteomyelitis in Diabetes Mellitus

XII. Imaging: Foot MRI

  1. CT Foot is an alternative, if MRI is contraindicated
  2. MRI or CT are preferred over bone scan
  3. Findings suggestive of Charcot Joint
    1. Periarticular Bone Marrow edema
      1. Progresses to cortical Fractures (and secondary deformity) if weight bearing continues
    2. Soft tissue edema
    3. Joint effusions
    4. Stress Fractures

XIII. Imaging: Normal studies that distinguish from other diagnoses

  1. Venous Duplex Ultrasound

XIV. Precautions

  1. Charcot Foot is often misdiagnosed as an alternative condition with delayed diagnosis on average, 7 months
    1. Consider in patients with recurrent "Cellulitis" (often improves transiently with bed rest)
  2. Delayed diagnosis is a risk for rigid foot deformities with significant amputation risk (RR 15-40)
  3. Involve specialty care early in course

XV. Management: General

  1. Step 1 Immobilization
    1. Total Contact Cast (TCC) or
    2. Prefabricated pneumatic walking brace (PPWB)
  2. Immobilize for 4 months until stable
    1. Erythema and edema resolved
    2. Affect limb with same Temperature as other limb
    3. Stabilization by XRay (repeat every 4-6 weeks)
  3. Step 2: Immobilize 6 to 24 months until foot stable
    1. Charcot Restraint Orthotic Walker (CROW)
      1. Indicated for anterior edema
    2. Ankle foot Orthosis
    3. Patellar tendon-bearing brace
  4. Step 3: Supportive Footwear
    1. Extra-deep shoes with custom insoles
  5. Additional treatment options
    1. Exostosectomy
      1. Stable chronic Charcot Foot with exostosis or ulcer
    2. TENS
    3. Low intensity Ultrasound
    4. Intranasal Calcitonin 200 IU (experimental)
      1. Bem (2006) Diabetes Care 29(6): 1392-4 [PubMed]
  6. Other measures that are ineffective
    1. Bisphosphonates
      1. Richard (2012) Diabetologia 55(5): 1258-64 +PMID:22361982 [PubMed]

XVI. Management: Total Contact Cast

  1. Contraindications
    1. Wagner Grade 3 Foot Ulcer (abscess or Osteomyelitis)
  2. Technique
    1. Tubular stockinette
    2. One quarter inch felt
    3. Three layer inner plastic shell
    4. Fiberglass outer shell
  3. Protocol
    1. Crutch walking only
    2. Initially change cast after first week (due to edema)
    3. Later change cast every 2-4 weeks

XVII. Management: Prefabricated pneumatic walking brace (PPWB)

  1. Indications
    1. Alternative to Total Contact Cast (above)
    2. Neuropathic plantar ulcer
  2. Contraindications
    1. Severe foot deformity
    2. Noncompliance

XVIII. Complications

  1. Rigid foot deformity
  2. Below the knee Amputation
  3. Foot Ulcer or plantar ulcer
    1. High risk for infection and Osteomyelitis
    2. Optimize foot wear to prevent Skin Ulcers
    3. Chronic ulcers are associated with a 5 year mortality >50%
      1. Yammire (2022) Foot Ankle Surg 28(8): 1170-6 [PubMed]
  4. Osteomyelitis
    1. Surgical Debridement AND
    2. Surgical correction of joint alignment and stability (Internal or external fixation)

XIX. References

  1. Augusta (2023) Crit Dec Emerg Med 37(1): 16-7
  2. Caputo (1997) Am Fam Physician 55(2):605-11 [PubMed]
  3. Marmolejo (2018) Am Fam Physician 97(9): 594-9 [PubMed]
  4. Myerson (1992) J Bone Joint Surg 74:261-9 [PubMed]
  5. Sommer (2001) Am Fam Physician 64(9):1591-8 [PubMed]
  6. Schon (1998) Clin Orthop 349:116-31 [PubMed]

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