Introduction of New Acetabular Designs Does Not Influence Risk of Early Failure in Hip Arthroplasty

Master thesis, Programme in Medicine, TITLE: Introduction of New Acetabular Designs Does Not Influence Risk of Early Failure in Hip Arthroplasty. Introduction According to a recent study there is an increased risk of early revision surgery when new implants are introduced in Finnish hospitals. Aim/Objective To investigate if the introduction of new primary or revision cups was associated with a temporary early risk of revision or re-revision when introduced in Swedish hospitals. Materials and Methods All primary total hip arthroplasties and first-time cup revisions recorded in The Swedish Hip Arthroplasty Register performed during years 1993-2011 were primarily included. Selection was based on a countrywide usage of at least 374 cases. The cup should not represent minimal modifications of a previously used design on the Swedish market. Further, only hospitals that had reported use of more than 50 cups of at least one of the designs selected were included. These selection criteria resulted in a total amount of 52,903 cups being analysed. All cups were given an order number based on the order in which the cup had been inserted in each hospital. The influence of order number of the cups was analysed in a regression model. Adjustments were made for potentially confounding covariates. Splines were applied to establish changes in risk of early revisions based on the order number. Revision within 2 years (n=902) was used as endpoint. Results The adjusted logistic regression analysis showed no increased risk of early revision surgery within 2 years during the implementation phase of new cups (p=0.97). According to the splines there was an increased risk of the first 120 cups and in cups being inserted with order numbers 281-600. Using the aforementioned numbers as cut off values did not change the risk of revision within two years (p≥0.14). Conclusion We were not able to demonstrate an increased risk of early revision when new cup designs are being introduced in Swedish hospitals. Keywords Swedish Hip Arthroplasty Register, total hip arthroplasty, implant introduction, implementation phase