Press-fit versus threaded acetabular cups in total hip arthroplasty: Functional and radiological results after five years.

Prospectively the outcome after total hip replacement with a new threaded acetabular cup design was compared to an established press-fit cup.After 1, 2 and 5 years, the 36-item Short Form Health Survey, Western Ontario and McMaster University Osteoarthritis Index and Harris Hip Score revealed no significant differences between the two groups (each group: n=42 patients), except for a higher Harris Hip Score in the threaded cup group after five years (p=0.02). After five years, one threaded cup had a mild radiolucent line without further signs of loosening. All other cups of both groups (98.6%) showed a full osseous integration. The cup inclination angle ranged from 41–58° (threaded cups) to 39–77° (press-fit cups).The new threaded cup provides equivalent clinical outcomes and osseous integration but more precise implant positioning compared to the press-fit design. No complications typically ascribed to threaded cups (acetabular fractures, bone resorption, nerve impairment) occurred