 The investigators are proposing to conduct this study to compare the ultrasonographic appearance of the sciatic nerve with their corresponding histologic architecture. Patients that are scheduled to undergo above knee amputation due to complications associated with diabetes will be enrolled. We intend to do an ultrasound examination of the sciatic nerve at its bifurcation about 4 inches above the knee. The investigators would mark the area on the skin where the image is obtained. Following surgery we will conduct a histologic examination of the nerve at the same site. 