Total hip arthroplasty (THA) is a routine procedure for the treatment of advanced hip joint damage. The long-term result of the prosthesis is mainly determined by migration or aseptic loosening caused by bone remodelling. Especially the migration of the artificial hip cup as a consequence of the remodelling process is a major problem. Patient-specific hip cups can be used to counteract this. However, individual hip cups are currently only implanted for the treatment of great deformations or tumours in the hip joint due to the cost-intensive manufacturing. The aim of this project is the development and establishment of a concept for the economical production of patient-individual prosthetic hip cups out of titanium sheets. This process consists of two steps. First, undersized cups of a universal acetabulum geometry are produced. In the second step a true-to-size enlargement of the produced universal cup prothesis is carried out by means of a modified adaptive rubber-die forming process. The development of this process is accompanied by a simulationbased planning of the production process as well as by a realization of a metal forming adapted design method. For the examination of the feasibility of the concept, CT-data of canine pelvis geoemtries are used because of the large number of CT data, which were aviable for the project. Furthermore it is planned, that the first manufactured prototypes will be tested using canine cadaver. In this study the planning of the manufacturing of the standardized titanium sheet metal components is carried out. For this two methods of producing the standardized hip cup were compared. The first method is a hydraulic forming; the second is a normal pressing process with a bunch die and a binder. Pure titanium was introduced in the simulation, which shows the same mechnical properties like the in prosthetics normally used titanium alloy TiAl6V5. The results of the process simulation of both methods showed that the reducing of the blank thickness is a problem of the manufacturing of the prosthesis. Because of that an adaption of the tool geometry was executed and the influence of the increase of the forming temperature at 200 C was examined. These simulations indicated, that the hydraulic forming seems to be a convenient method to produce the prosthetic acetabulum. The first part of the metal forming adapted design method is the deduction of a universal acetabulum geometry, which has to be designed for the production of the standardized component. This deduction shall be realized by means of a superposition of 3D models of pelvis geometries. For this, two different superposition methods were compared and the Best Fit method was determined as the suitable method. By means of the Best fit method a first universal geometry was created.

608 adaptiven Knochenumbaus nach wie vor ein großes Problem dar. Patientenindividuelle Prothesen bieten eine mögliche Lösung für dieses Problem. Einzelne individualisierte Hüftpfannen werden jedoch nur für die Behandlung von massiven Deformitäten oder Tumoren eingesetzt. Ziel dieser Studie ist ein innovatives Konzept für die Herstellung von patientenspezifischen Hüftprothesen aus Titanblechen zu entwickeln. Methoden: Zur Realisierung des innovativen Konzepts, wurde eine reproduzierbare Designmethode basierend auf 13 ursprünglichen menschlichen Geometrien entwickelt. Mit Hilfe dieser Methode wurde eine standardisierte menschliche Hüftpfannenprothese erzeugt. Beruhend auf diesem Entwurf wurde eine Hüftpfanne mittels eines entwickelten Hochdruck-Blechumformungsverfahrens hergestellt. Die Entwicklung dieses Verfahrens wurde mit Hilfe der Finite-Elemente-Methode konzeptioniert. Ergebnisse: Der Vergleich der Simulationsergebnisse mit der geometrischen Vermessung der hergestellten Hüftpfannen führt zu einer Standardabweichung von 0,404 mm. Weiterhin zeigt die Implantation der Prothese in ein synthetisches Knochenmodell eine zufriedenstellende Passgenauigkeit am Rand des Acetabulum. Fazit: Das Hochdruckblechumformungsverfahren ist für die Herstellung der entworfenen, standardisierten Hüftpfannenprothesen geeignet. Jedoch ist eine weitere Optimierung weiterhin notwendig.

Abstract:The revision of an hip prosthesis can have diffrent reasons. One frequent cause, especialley after implantation of a conventional cup, is the so called stress-shielding effect which can lead to a migration or loosening. Patientspecific 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 a patient-specific hip cup prosthesis has to be developed and manufactured. Besides the numerical design by means of a coupling between multi-body simulation (MBS) and finite element method (FEM), an inovative concept for the production of patientindividual hip prosthesis out of titanium sheets is introduced in this study.Patient-individual hip cups, bone remodelling, reverse engineering, process planning, sheet metal forming

A new method is developed to map the prosthetic migration in the pelvis. Using mechanical relationships and remeshing regulations the finite-element-analysis (FEA) calculates the possible migration of the cup in pelvis. This method was applied to polyethylene cup and showed good results in comparison with a clinical study. In order to increase the accuracy of the numerical model, the difference in hip contact forces caused by the migration of the cup is calculated by multi body simulation and embedded in the FEA using online coupling software developed by our scientific group.