The objective is to show a better efficiency of Sorbact TM (trademark) dressings compared to Alginates that are standardized dressings after pilonidal sinus excision during a period of 75 days. The main objective is to show a difference of 20% of wounds completely healed in 75 days between the two types of dressing: 50% of wounds healed with Algosteril TM compared to 70% of wounds healed with Sorbact TM.