Anatomical Background for the Development of Preformed Cranioplasty Implants

Preformed cranioplasty implants form a new concept of implants to repair relatively large-sized calvarial defects. They could offer an alternative treatment to manually molded cranioplasty, and to flat or patient specific implants, while still achieving a satisfactory clinical result. We report on 3D statistical modeling and analysis performed in 80 clinical CT data of adult European Whites with unaffected calvarial bones to establish an anatomical background for the development of preformed alloplastic cranioplasty implants. Most size and shape (=form) variation was observed bilateral symmetrically in the central temporal region, showing up to 26.8 mm variation and 9.4 mm standard deviation from the mean form. Large deviation was also observed in the central lower forehead, in the central occipital region at the protuberantia occipitalis externa and laterally to it. An intermediate variation was detected at the transition area from the temporal to other regions, as well as in the frontal and occipital area. The cranial roof, the temporal fossa, and the nuchal region exhibited the lowest variability with a standard deviation of about 4 mm. Principal components analysis revealed no relevant shape but a significant size difference between genders. Size contributed to 24.4% of the overall form variability. The mean surface area difference between genders was 67 cm(2). The size and number of implant forms required have to be referred to the relatively large anatomical variation experienced, and also to considerations related to implant location, design, and material. A rigid material is considered to significantly increase the number of implants forms, especially when repairing relatively large-sized defects.