Cause:

1. cellular injury + necrosis from freezing process
2. cessation of circulation ← cellular aggregates and thrombi forming as a result of exposure to low temperatures below –13° C (usually cold air)

• firm white numb areas in cutis (separation of epidermal-dermal interface)

Location: feet, hands (thumb commonly spared ← protection by clenched fist)

Early changes:

• soft-tissue swelling + loss of tissue at tips of digits

CHILD

• fragmentation / premature fusion / destruction of distal phalangeal epiphyses
• secondary infection, articular cartilage injury, joint space narrowing, sclerosis, osteophytosis of DIP
• shortening + deviation / deformity of fingers

ADULT

• osteoporosis (4–10 weeks after injury)
• periostitis
• acromutilation ← osteomyelitis + surgical removal + tuftal resorption ← soft-tissue loss
• small round punched-out areas near edge of joint
• interphalangeal joint abnormalities (simulating osteoarthritis)
• calcification / ossification of pinna

Angio:

• vasospasm, stenosis, occlusion
• proliferation of arterial + venous collaterals (in recovery phase)

Bone scintigraphy:

• persistent absence of uptake (= lack of vascular perfusion) indicates nonviable tissue

Rx: selective angiography with intraarterial reserpine