HIDE: a new hybrid environment for the design of custom-made hip prosthesis

This technical note describes a new software environment (HIPCOM design env ironment, HIDE) for the design of custom-made total hip replacements. These devices are frequently designed using general-purpose mechanical computer- aided design (CAD) programs using a set of bone contours extracted from the computer tomography (CT) images as anatomical reference. On the contrary, the HIDE system was developed to let the operator directly design the stem shape onto the CT images in a single-step operation. The operator can direc tly import CT data in DICOM format or use special functions to reconvert to a digital stack, the CT images printed on a radiological film. Once the st ack of CT images is loaded, the operator can design the implant shape by im posing control sections directly on the CT images. The interpolation of the se control sections produces the basic 3D shape of the custom-made stem. Th e shape is then exported to the CAD-computer-aided manufacturing (CAM) prog ram to refine the design and to generate the part program to manufacture th e implant with a CNC tooling machine. Using HIDE, the duration of design st eps it affected was reduced by more than 50% with respect to the standard m ethod in use at the manufacturer site. HIDE also improved the accuracy and the repeatability of the whole procedure. The learning curve became flat af ter only ten cases. These good results were achieved because of the integra tion of the vectorial description of the prosthetic component with the rast er description of the CT data that allowed the designer to use all details available in the CT images. (C) 2001 Elsevier Science Ireland Ltd. All righ ts reserved.