After the introduction of Redon high-vacuum drainage, a considerable decrease in post-operative haematomas has been noted. But some of the complications could not be prevented by using the Redon system. They were in fact the result of it. The Redon system cannot be classified as a "closed" wound drainage. During bottle replacement, the system must be disconnected. An effective closed system must remain absolutely tight from application to removal of the drain so no possibility exists of contamination infection from the outside. After introduction of a continuously absolutely closed system in a prospective study with 3 different systems the influence after hip joint arthroplasty operations on wound healing was investigated. The wounds were drained with the Redon high-vacuum system or the newly developed, permanently closed drainage system with maximum obtainable low pressure of 80% vacuum and 50% vacuum. Here the maximum obtainable vacuum builds up slowly in relation to the accumulated amount of wound fluids. The loss of low pressure in Redon systems differs between the drains. In the intra-articular drains the mixture of air and blood results in a linear decrease and follows not a hyperbola like in subcutaneous drains. Because of the high suction at the beginning of the Redon drainage necrotic muscle cells adhere to the outside of the drain openings and clogs them up mechanically. The stronger the suction effect on the tissue, the more fatty live cells and small vessels enter the lumen of the drain in the Redon system and 80% vacuum. This mechanisms result in bleeding from the drain canal after removal of the drain and "secondary" haematomas. In the absolutely continuously closed system with maximum obtainable low pressure of 50% vacuum increased suction, lowered bleeding after removal of the drain and best healing results were observed. The 9.8% Cfu occurrence on Redon drains after removal found in the study is within the lower average figures given in literature while the 0.9% figure with both closed systems was never reached before.