Classification of frostbite injuries

Frostbite injuries can be classified into grades 1 to 4 depending on the clinical presentation after rewarming (1,2)

• grades 1 to 2 comprising superficial frostbite injuries
  • grade 1, cyanosis is absent, and the risk of amputation is minimal
  • grade 2 frostbite presents with cyanosis on the distal phalanx of fingers or toes, and is associated with a moderate risk of amputation
• grades 3 to 4 deep frostbite injuries
  • grade 3 frostbite injury
    • cyanosis up to the metacarpophalangeal joint (MCP; base of the fingers) or metatarsophalangeal joint (MTP; middle of the foot)
    • bears a high risk of amputation
  • grade 4 injuries
    • cyanosis is seen proximal to the MCP or MTP joint
    • the risk of amputation is almost 100%

Reference:

1. Sheridan RL, Goverman JM, Walker TG. Diagnosis and treatment of frostbite. N Engl J Med. 2022 Jun 9;386(23):2213-20.
2. McIntosh SE, Freer L, Grissom CK, et al. Wilderness Medical Society clinical practice guidelines for the prevention and treatment of frostbite: 2024 update. Wilderness Environ Med. 2024 Jun;35(2):183-97.