Development and first experience with an uncemented press-fit cup.

A new cup with a new concept of cementless fixation and new coating was designed to obtain primary stability by a press-fit mechanism. The press-fit mechanism is achieved by flattening the dome of the hemispheric cup and by using a cup size with an outer diameter 1.5 mm larger than the reamer used last. 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 advantages of the press-fit cup are the excellent adaptation with minimal resection and the preservation of the subchondral bone. The preparation of the acetabulum is easy (reaming only), no additional fixation by screws is necessary, and only a few instruments are needed. The results of 81 total hip arthoplasties using the press-fit cup and having an observation period ranging from 12 to 24 months show no clinical or roentgenographic loosening. No intraoperative or postoperative complications because of the press-fit cup were seen.