Computer aided design of large-format prefabricated cranial plates

The authors' objective in this project was to replace current state-of-the-art manual methods for preoperative production (i.e., prefabrication) of large-format (>100 cm2) cranioplasties with a system for computer-aided design and direct computer-aided manufacture of the implant's shape. This system uses standard 3D CT data, requires no specialized training, and produces an accurately fitting cranioplasty that can be recast in the physician's material of choice (e.g., polymethylmethacrylate [PMMA] or pre-bent titanium plating). The authors begin by locating the cranial defect margin on a skull surface image generated from a 3D head CT-scan. A right-to-left mirrored or average 3D skull surface template image is then fit to the patient's skull surface image. The area around the defect is cut out and stitched to the previously isolated defect margin. This defect-filling surface is then tapered and 3D printed. The 3D printed implant model is then recast in a biocompatible material. Manually generated cranial implants produced for five patients were compared with implants resulting from this new computer-based method. All five computer-generated implants were better fitting and more cosmetically suitable than the manually generated skull plates received by these patients. These well-fitting implants are more likely to protect the brain from trauma and infection. Therefore, the authors conclude that their new production method provides a better result with less expense than current methods for preoperative or intraoperative fabrication of large-format cranioplasties.