Principles of acetabular fixation in THR with special reference to the "press-fit cup".

The "press-fit cup" has been developed by the author according to the current well known principles of cementless fixation of acetabular cups in THR. Its concept is to achieve primary stability through press-fit, by flattening the dome of the hemispheric cup and by using a cup size 1.5 mm larger than the reamer used previously. The coating (Sulmesh) consists of a net shell of four layers of orderly oriented wire meshes with specific pore size and porosity volume. The pure titanium wires are bonded together. The histologies of retrieved cups shows extensive bony ingrowth both in animal experiments and in autopsy specimens. In a radiological follow-up of 100 consecutive primary total hip replacements, the press-fit cup showed complete radiological integration in all 3 zones in 97% of cases. Nonprogressive radiolucencies were found in zones I and III in only 3% of cases.