1. To explore the pathology of nerve, vascular, and skin in the amputated leg
2. To diagnose small-fiber sensory neuropathy of the contralateral leg by investigating the skin intervention
3. To search for (1) mechanisms of amputation and (2) prevention measures for further amputation in the currently healthy-looking limb

Diabetic foot occurs in 15% of diabetic population (3) and 15% of the diabetic foot patients end up with lower limb amputation. Peripheral neuropathy (sensory, motor and autonomic), peripheral vascular disease, trauma, infection and poor wound healing all contribute to diabetic foot problem.

Peripheral neuropathy could be evaluated in a variety of ways, including vibratory thresholds, thermal thresholds, pressure perception thresholds, muscle strength. All these predict foot ulceration to some degree(1). Motor nerve conduction velocity is an independent predictor for the development of new foot ulcer in diabetic population.

For more detailed structural study of neuropathy in diabetic patient, we could use skin biopsy method. Skin biopsy with PGP9.5 immunohistochemistry has been demonstrated by ultrastructural studies to label the terminal portions of both small myelinated and unmyelinated nerve in the epidermis . Intra-epidermal nerve fiber (IENF) density is reduced in patient with impaired glucose tolerance and clinically overt diabetes . Previous IENF density study was performed in diabetic patients with sensory symptom but no foot ulcer. Now we tried to evaluate IENF density in severe diabetic foot patient who received below knee amputation. Skin biopsy willl be performed at amputated leg. The skin biopsy area will be located at lateral side of distal leg, 10 cm above the lateral malleolus as previous protocol of our group . Underlying sural nerve and posterior tibial nerve will be also harvested for further ultra-structural study. The result will be compared to the control group which were recruited from a previously described cohort matched by gender and age.

Inclusion Criteria:

• Diabetic foot wound patient who underwent below-knee amputation

Exclusion Criteria:

• Diabetic foot wound patient who couldn't receive below-knee amputation due to severe heart disease, high anesthetic risk.

Diabetic foot wound patient who underwent below-knee amputation due to poor wound healing and severe infection condition. The patient population often receives leg revasculariztion surgery but poor response for wound healing.