Development of a new operative 3D printed template-cranioplasty-concept for performing craniotomy in the posterior cranial fossa and validation of the system using a 3D printed simulation model: a preclinical feasibility study

BACKGROUND: The retrosigmoid approach is a standard surgical route used for the treatment of various tumors and vascular lesions in the cerebellopontine angle. However, postoperative reconstruction of the surgical defect could remain challenging, particularly in cases requiring intraoperative extension. For this reason, a novel concept was developed to define the surgical approach and enable precise defect coverage using a patient-specific implant. This concept was designed to be patient-specific and realized through 3D printing. METHODS: The developed 3D printed template-implant concept was designed to facilitate precise craniotomy. The template is used as a stencil and a surgical marker is applied to delineate the implant contours directly on the patient's skull. This outline subsequently serves as a guide for where to perform the craniotomy and defines its boundaries. The custom-fit implant replicates the template design and ensures complete coverage of the craniotomy defect, while allowing intraoperative adjustment if required. Preclinical testing was conducted on a 3D printed simulation model representing the posterior cranial fossa (surgical area). The novel concept was tested by nine senior and attending neurosurgeons from the University Hospital Leipzig. Bilateral craniotomies were performed using the template and subsequently closed with the implant. The fit of the implant was evaluated using CT scans. The time required for preparation, including craniotomy, as well as for post-procedure handling, including implant placement, was recorded. RESULTS: The average gap of the new concept was 2.11 mm, which was significantly smaller than that of the current standard approach (5.52 mm) and showed lower variability. The entire procedure, including craniotomy and implant placement, took an average of 13 min and 20 s. CONCLUSION: The novel template-implant concept for retrosigmoid approaches improves defect coverage and reduces gap sizes. Furthermore, it demonstrates the potential of 3D printed patient-specific implants for more precise and predictable surgical procedures, although further studies are required to validate efficiency and clinical safety.