Comparison of titanium and stainless steel, Greenfield vena caval filters.

The standard stainless steel Greenfield filter (SGF) requires a 24F-sized carrier system, and its insertion percutaneously has been associated with local venous thrombosis. To facilitate both percutaneous and operative insertion, a titanium model of the Greenfield filter (TGF) has been developed that allows use of a 12F-sized carrier system. Mechanical comparison of the SGF and TGF devices shows that both withstand extensive flexion stress, but the TGF has greater endurance (52 gm at 20 mm travel) than the SGF (48 gm at 5 mm travel). Measurement of lateral forces for fixation shows comparable force (4.5 gm) at 22 mm for each device but greater force for the TGF at diameters more than 22 mm to its resting diameter of 38 mm. The TGF also withstands crevice corrosion in hydrochloric acid and ferric chloride better than the SGF. Animal studies in 20 sheep show comparable fixation of both devices with no added thrombogenicity of the TGF. Thrombus capture and resolution studies after 14 days in dogs show comparable effectiveness, and histologic examination of the venae cavae show similar inflammatory cell reaction and fibrosis with no foreign body reaction for either metal. Both the SGF and the TGF demonstrate durability and effective filtration of thrombi, with the TGF having the added advantages of ease of insertion and potential improved fixation in larger cavae.