HOW MUCH STABILITY DO WE NEED IN THE 1 MM PRESS-FIT IMPLANTATION OF A POROUS-COATED ACETABULAR COMPONENT WITHOUT SCREWS DURING SURGERY?

Abstract

Background: Press-fit implantation of a porous-coated acetabular component without screws can be used for total hip arthroplasty (THA). The purpose of this report is to determine adequate initial stability of the acetabular component by applying a novel method would allow us to avoid screw use and to evaluate the outcomes of an oversized hemispherical cup using the 1 mm press-fit technique. Methods: We retrospectively evaluated 119 consecutive patients who underwent THA from February 2011 to June 2015. The intra-operative stability of fixation was checked by trying to pull the metal shell out of the acetabulum using the shell holder (pull-out test). We confirmed these tests using a digital hand scale. When we reached 9 to 10 kg (1 kg = 9.81 N), we showed that the acetabular shell achieved good stability. Kaplan-Meier survivorship analysis was performed to calculate the survival rate of the acetabular component. Results: The mean follow-up was 6.9 years (5–10 years). No component was revised because of loosening, and all implants were radiologically stable within the observation period. One socket had been revised because of failure of dislocation, which had [Formula: see text] acetabular inclination. There was an acetabular fracture in one hip, which was operated on prior to THA. Conclusions: We used a new method to assess the initial stability gained using the press-fit technique, which may allow the surgeon to determine whether adequate initial stability is achieved. Cup position has a significant impact on the risk of revision of press-fit cementless acetabular component. The risk for early failure can be decreased by optimal cup positioning during primary implantation. In addition, while a stable bone-implant connection is desirable, fracture of the acetabulum can be avoided using the 1 mm press-fit technique.