Is there still a role for threaded acetabular cups?

Introduction: Total hip arthroplasty (THA) is 1 of the most common procedures in orthopaedic surgery. Different options and implants are currently available. Uncemented hip cups need primary stability for bone ingrowth, the use of screws is required when the desired stability is not achieved. Another option is the use of a hemispherical threaded cup with enhanced primary stability. The purpose of our study was to compare the results of a 3rd-generation threaded cup versus a press-fit cup with a long track record. Materials and methods: A consecutive series of 300 THAs performed by 2 surgeons was retrospectively reviewed, 150 press-fit cups and 150 screwed cups. Minimum follow-up 27 months; maximum 78 months (mean 52.5 months). The primary endpoint was a stable and painless THA, secondary endpoints included Hip disability and Osteoarthritis Outcome Score, Junior and radiographic evaluation. Results: Preliminary results showed no statistically significant differences between the 2 groups for all the evaluated parameters, the number of early mechanical loosening was higher for press-fit cups, but this value was not statistically significant. At a mean follow-up of 52.5 months 1 cup revision (0.3%) was seen in the screwed cup group and 2 (0.6%) in the press-fit cup; these results were not statistically significant. Discussion and conclusion: The main concern for screwed cups is the greater bone loss and possible removal difficulties during revision surgery. This study has some limitations, in particular regarding follow-up, but is still ongoing. Our results showed no difference between the 2 systems.