A Prospective, Randomized, Controlled Trial of Autologous Platelet-Rich Plasma Gel to treat refractory dermal ulcer

INTERVENTION: Experimental group:Based on standard treatment, Platelet‐rich plasma;Control group:Standard treatment consists of daily topical washing, cleaning, debridement and dressing changing of the wounds.; CONDITION: refractory dermal ulcer PRIMARY OUTCOME: variation of ulcer area and volume; SECONDARY OUTCOME: Blood and urine routine examination, blood glucose; INCLUSION CRITERIA: 1. After standard therapy of dermal ulcer for 2‐6 weeks, it is ineffective; 2. ABI>=0.6 or good blood supply to the ulcer. If ABI<0.6, blood supply is improved after interventional or surgery therapy; 3. Fasting blood glucose<=8mmol/L, Postprandial blood glucose<=11mmol/L; 4. Infection or osteomyelitis are well controlled; 5. Blood pressure<=160/90mmHg; 6. Immunosuppressor is not used or its dosage is maintained in recent three weeks; 7. No severe heart, lung, liver and renal dysfunctions or blood disease; 8. No psychological disease. The patient can understand the aims and potential adverse events of this clinical trial completely and sign the information consent form.