Computer Based Algorithm for Patient Specific Implants for Cranioplasty in Patients With Skull Defects

Patients with skull defects after craniotomy for example tumor resection, head trauma, stroke, need a reimplantation of the bone afterwards. For some circumstances, their own bone cannot be reimplanted due to infection, tumor infiltration, damage to the bone, or aseptic bone necrosis. In these cases a Patient Specific Implant (PSI) needs to be designed to fit into the patient's skull defect. The design of the PSI is based on the preoperative CT-scan of the patient's head with the skull defect, the imaging data set is uploaded and processed with IPlanNet software by BrainLab®. With the help of the software, a 3D model of a negative mould of the PSI is designed and printed. In the operation room, the PSI is fabricated under sterile conditions using the PSI mould. The design of the PSI mould with the help of IPlanNet is demanding and takes some few hours depending on the complexity of the case to be designed. In certain cases the accuracy of the fabricated PSI mould is not optimal, so that the surgeon intraoperatively has to adapt for the inaccuracy to achieve the best cosmetic and functional results at the expense of the operation duration, a known risk factor for postoperative wound infection and other perioperative complications. 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 cosme