The Customized Artificial Hip Cup: Design and Manufacturing of an Innovative Prosthesis

Abstract

The demand for customized products has increased in recent years and will become even more important in the future. This trend is mainly observed for the medical technology sector influenced by the increasing manufacturing of patient-individual prostheses. In particular the manufacturing of customized hip cups is gaining in importance. Over 800,000 total hip replacements are performed worldwide each year. Despite this experience, the migration and loosening of the hip prosthesis especially of the cup due to the bone resorption caused by stress shielding is a current problem. Patient-specific hip cups can be used to counteract this. However, individual hip cups are only implanted for the treatment of great deformations or tumours because of the cost-intensive manufacturing. Within this project the remodelling process is calculated with a conventional prosthesis via finite element method (FEM) coupled with multi-body simulation (MBS). A migration of the cup in the proximal direction can be suggested. Based on these results an innovative and economic concept for the design and production of patient-individual hip cups for primary surgery by means of sheet metal forming is developed. In this two-stage process first standardized titanium sheet metal components are produced. Then a true-size enlargement of these components is executed by a modified adaptive rubber-die forming process. The development is accompanied by an FE simulation-based planning as well as a metal forming adapted design method. In this study the first part of the design method is demonstrated, which contains the deduction of a universal acetabular geometry, necessary for the production of the standardized component. Furthermore, high pressure sheet metal forming (HPF) will be introduced for the manufacturing of standardized components. Therefore an FE-simulation of the process is carried out for the design of the forming tool.