Konsentrasi Hypoxia-Inducible Factor 1-Alpha, Ekspresi Vascular Endothelial Growth Factor, dan Kepadatan Vaskularisasi Jaringan di Kaki Luka Diabetik yang Menjalani Amputasi dan Non-Amputasi = Hypoxia-Inducible Factor 1-Alpha Concentration, Vascular Endothelial Growth Factor Expression, and Tissue Vascularization Density of Amputated and Non-amputated Diabetic Foot Ulcer