Cementless press-fit cup: principles, experimental data, and three-year follow-up study

The concept of the press-fit cup includes an operative defect as small as possible, achievement of intrinsic stability by press-fit, and surface coating by an orderly, oriented wire mesh coating. The design is a modified hemisphere with flattening in the pole area and oversized cup diameter. A first series of press-fit cups were fitted with titanium nitride-coated stainless steel mesh. The manufacturing of such chemically pure titanium has only recently become feasible. Animal experiments using mountain sheep have shown an increase in the stability of the press-fit cup within the acetabulum with time and progressive bony ingrowth; this was verified in cups retrieved at autopsy. Three hundred eighty-seven first-generation titanium nitride-coated stainless steel mesh implants have been reviewed with a follow-up time of 12 to 39 months (average, 16.6 months). There were no intraoperative complications related to the cup. The roentgenographic follow-up study of 330 (85.1%) hips showed only a single case with a radiolucent line in all zones (1-3) as a roentgenographic sign of loosening, i.e., fibrous ingrowth. Two cups had to be revised due to insufficient primary stability and tilting.