Therefore, the investigators have developed an automated computer-based algorithm for PSI design (CAPSID). With the help of this tool, an accurate PSI and its corresponding mould can be calculated and designed based on the preoperative CT scan of the patient within 5-15 minutes and the corresponding mould can be printed. This step is automated and thus, independent of the neurosurgeons experience and skills in 3D processing software. The mould can be used for intraoperative fabrication of the implant under sterile conditions in the common way as described above. The possible advantages of the clinical establishment of this procedure would be a higher accuracy of the PSI compared to the conventional PSI fabrication method with better cosmetic results, lower costs and faster availability and production leading to shorter waiting time for the patient, and as a consequence of the higher accuracy leading to shorter operation time, with a reduction of risk of operative adverse events for the patient. Furthermore, the proof of practicability of this new method, could lead to new concepts in the field of Computer-based Patient Specific Implants in modern medicine in general. A clinical trial is necessary to proof the advantages and practicability of the investigators' concept of computer-based algorithm for PSI design (CAPSID) for patients with skull defects.