A data processing method performed by a computer (2) for determining the structure of a medical implant (12 18 20 22) which is to replace removed tissue in a patients body, comprising the steps of:—acquiring a 3D dataset which represents remaining tissue (10 17) which at least partly surrounded the removed tissue before the latter was removed—determining the required contour of the implant (12 18 20 22) from the 3D dataset—simulating forces exerted by the remaining tissue (10 17) on the contour of the implant (12 18 2022) and—determining a structure dataset which represents the structure of the implant (12 18 20 22) such that the implant (12 18 20 22) has the required contour and can absorb the simulated forces.
