Autologous Skin Substitute for leg ulcers

INTERVENTION: Application of skin substitute or acellulair dermis at week 0 and week 1. CONDITION: Chronic (arterio) venous leg ulcers ; ; PRIMARY OUTCOME: 1. Efficacy (Time to heal: time point of healing, Number and percentage of closed ulcers at week 12 and 26);; ; 2. Ulcer size: Percentage of reduction;; ; 3. Safety. SECONDARY OUTCOME: 1. Recurrence (Number and percentage of recurred ulcers at 3 and 6); ; ; 2. Duration of closure; ; ; 3. Quality of the healed skin; ; ; 4. Quality of life will; ; ; 5. Take rate of skin substitute. INCLUSION CRITERIA: 1. Presence of confirmed venous, arterio‐venous ulcer; 2. Patients age over 18 years and under age of 90 years; 3. Ulcer duration over 12 weeks and less than 5 years consecutively; 4. <15% ulcer size reduction in 4 weeks prior to inclusion; 5. Ulcer is between 1‐40 cm2 in size; 6. ABPI = 0.7 and < 1.2; 7. Ulcer depth < 1 cm; 8. Mobile, at least able to walk with medical walker, and able to return for required treatments and study evaluations; 9. (Legally) capable to give informed consent; 10. Able to understand and comply with requirements of study protocol.