Computer-assisted design and rapid prototyping technology for the underlay of hemifacial atrophy / 中国组织工程研究

ABSTRACT

BACKGROUND: There are many methods for repairing the hemifacial atrophy, the most common is preparing plaster facial mold of the patient, with wax piled on the surface to restore the patient's facial shape, and wax pattern serves as a reference of surgical pad. However, the therapeutic effect for the correction and treatment is not satisfactory due to varied abnormality and difficult plans.OBJECTIVE: To discuss the feasibility of manufacturing underlay for the treatment of hemifacial atrophy using computer-assisted design and rapid prototyping technology. METHODS: Skull of the hemifacial atrophy patient was scanned with Picker 6000 SCT, and the data obtained were processed in Voxel Q image workstation for 3-D reconstruction with volume rendering technique. After the interval lamination, the images were downloaded at 0.4-mm interval in a BMP format using CuteFTP 4.0 software. Then the transaxial 2-D image data were converted into digitized 2-D contour data by using image processing software developed by experimental team through a series of processes, including filtering, screening, noise reduction, and distortion correction. The edges and contour of the images was extracted to obtain a vector diagram of facial cranial cortical bone contour line. The digitized data were inputted into image processing software of Surfacer 9.0 for vector superposing, thus the 3-D wire frame and solid images of skull could be reconstructed. According to mirror-image symmetry relation, the point-cloud data of facial bone on the normal side was duplicated to the atrophied side. Thus a 3-D model of the underlay was produced between the atrophied bone and the mirror image of normal side. In order to compensate the atrophy of soft tissues, the model was designed 1.5 mm thicker. After the three-dimensional Surfacer data on the CAD were re-stratified, the contour editing of the underlay and the supporting set of prototype were completed in RpDataRepare, forming RP files and creating underlay template through rapidly output of the processing file for rapid prototyping required, as a reference of surgical procedures.RESULTS AND CONCLUSION: The 3-D solid model of the patient skull bone surface contour was obtained and simulacrum of the underlay was prepared with computer assistance and rapid prototyping. According to the simulacrum, the operation was carried out and got a satisfactory result. The manufacture of underlay for the treatment of hemifacial atrophy could be accomplished by computer assisted design and rapid prototyping in a highly precise and rapid manner. It is a promising technique in the field of individualized underlay making in craniofacial surgery.