Objective To study the generating algorithm of personalized external fixation model based on STL file, so as to realize the fabrication of personalized external fixation through 3D scanning, model generation and 3D printing. Compared with the traditional plaster fixation, the external fixation obtained by the proposed method has the advantages of good adhesion to the external surface of the limb, good gas permeability and light weight. Methods In order to generate a personalized external fixation model, the key generating algorithms of the model were studied. The point cloud file of the residual limb was obtained by a 3D scanner, and then was converted into an STL format file. The triangular patches were processed by cutting, offsetting, triangulating and hollowing to create an external fixation model with good gas permeability and conformable surface that is fully fitted with the body surface. Finally, the external fixation was fabricated by 3D printing. Results Using the improved point offset algorithm, the problem of severe distortion of the point offset at the plane and sharp corners was solved. Using the tangent sort method, the points on the contour ring were sorted clockwise to obtain a triangular profile. The hollowing of the model was achieved by using the typical three-dimensional "cutting tool" mathematical model and the STL file space intersection method. Conclusions The improved model generating algorithm was validated based on a wrist case, and the personalized external fixed fixation model with conformable surface was obtained. It is proved that the proposed model generating algorithm is effective and practical.

3D printing technology has unique advantages and broad application prospect in biomedicine field. In recent years, cell printing, tissue printing, and organ printing technologies h have appeared successively, and drug printing and medical device printing have been realized. For complex surgical cases, surgeons and researchers have explored a surgical program that involves 3D printing technology, and completed many clinical applications including case discussions, surgical simulations and implantation surgeries. These efforts promoted the application and development of 3D printing technology in medical field. The purpose of this paper is to describe the application and research status of 3D printing technology in medical field from the aspects of medical teaching, orthopedic surgery, stomatology, bioprinting, drug printing, medical device manufacturing, etc., and put forward the prospects for future development.