3D surface accuracy of CAD generated skull defect contour.

The creation of a satisfactory cosmetic outcome in the repair of cranial defects relies on manual skill. However, computer aided design is gaining acceptance in the creation of custom cranial implants. The purpose of this work is to demonstrate the accuracy of a CAD generated skull defect contours using 3D difference maps. 3D multi-slice CT scanning was carried out on a life size plastic skull. Surface models were generated of the original skull and of temporofrontal and parietal defects. Surface contours were interpolated towards the centre of the defect from the edges where it was blended. The CAD contour deviation ranged from 0.0 mm to 2.0 mm with 80% of the total defect area less than 0.66 mm as measured by difference maps. CAD techniques can be used to produce contours for the repair of cranial defects with minimum deviation from the original skull contour. This enables accurate design and production of cranial implants.