MIGRATION PATTERN OF PRESS FIT CUPS IN THE PRESENCE OF STABILIZING SCREWS

Abstract

Introduction: The use of screw fixation for cementless porous-coated acetabular components for primary total hip arthroplasty (THA) remains controversial. Aim of this study was to evaluate initial acetabular implant stability and late acetabular implant migration with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary THA.

Methods: In a prospective study, 102 patients (107 hips) were available for follow up after primary THA using a cementless, porous-coated acetabular component. Patients were followed up at 6 and 12 weeks, 6 and 12 months and annually thereafter to an average of 2.6 ± 1.7 years. A total of 428 standardized radiographs were analyzed by the Einzel-Bild-Röntgen-Analyse (EBRA)-digital method. Additionally, the Harris Hip Score (HHS, 0–100) was assessed at the latest follow-up.

Results: 101 (94.4 %) implants did not show significant migration of more than 1 mm of the acetabular component. Six (5.6%) implants showed a migration of more than 1 mm: in 3 cases (2.8%), migration was progressive during follow-up and led to a revision surgery due to aseptic loosening. In 3 cases, migration came to a halt and cups were claimed stable. Individuals without cup migration had an average HHS of 78.4 ± 22.9, whereas patients who showed a cup migration of > 1 mm had 53.3 ± 24.2. Statistical analysis did not reveal preoperative patterns that would identify future migration.

Discussion: and Conclusion: Our findings show that the use of screw fixation for cementless porous-coated acetabular components for primary THA does not prevent cup migration.