Computer-aided manufacturing of implants for the repair of large cranial defects: an improvement of the stereolithography technique.

The objective of this study is to demonstrate the utility of geometric modeling in cranioplasty; in other words, to use geometric modeling to generate a prototype that will be used as the base structure of a composite prosthesis for covering cranial defects. This geometric model is easy to manipulate and can be modified. To achieve this goal, the top surface of a cranial bone flap is digitized using a portable coordinate measurement machine. Intentionally, a sub-surface of the bone flap, representing the skull defect, was not digitized. A geometric model of the bone flap is generated that includes the undigitized region. With the technique described in this paper the authors generated the geometric model of the undigitized region (the skull defect). The geometric model of the bone flap is further manipulated and a series of conical cavities are introduced. Prototypes of the geometric models are manufactured using stereolithography. The clinical implications of this technique are discussed.