We improved the geometrical modeling procedure for fast and accurate reconstruction of orthopedic structures. This procedure consists of medical image segmentation, three-dimensional geometrical reconstruction, and assignment of material properties. The patient-specific orthopedic structures reconstructed by this improved procedure can be used in the virtual surgical planning, 3D printing of real orthopedic structures and finite element analysis. A conventional modeling consists of: image segmentation, geometrical reconstruction, mesh generation, and assignment of material properties. The present study modified the conventional method to enhance software operating procedures. Patient's CT images of different bones were acquired and subsequently reconstructed to give models. The reconstruction procedures were three-dimensional image segmentation, modification of the edge length and quantity of meshes, and the assignment of material properties according to the intensity of gravy value. We compared the performance of our procedures to the conventional procedures modeling in terms of software operating time, success rate and mesh quality. Our proposed framework has the following improvements in the geometrical modeling: (1) processing time: (femur: 87.16 ± 5.90 %; pelvis: 80.16 ± 7.67 %; thoracic vertebra: 17.81 ± 4.36 %; P < 0.05); (2) least volume reduction (femur: 0.26 ± 0.06 %; pelvis: 0.70 ± 0.47, thoracic vertebra: 3.70 ± 1.75 %; P < 0.01) and (3) mesh quality in terms of aspect ratio (femur: 8.00 ± 7.38 %; pelvis: 17.70 ± 9.82 %; thoracic vertebra: 13.93 ± 9.79 %; P < 0.05) and maximum angle (femur: 4.90 ± 5.28 %; pelvis: 17.20 ± 19.29 %; thoracic vertebra: 3.86 ± 3.82 %; P < 0.05). Our proposed patient-specific geometrical modeling requires less operating time and workload, but the orthopedic structures were generated at a higher rate of success as compared with the conventional method. It is expected to benefit the surgical planning of orthopedic structures with less operating time and high accuracy of modeling.

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This study was aimed to compare the biomechanical characteristics between the personalized plate system and the existing plate system in the internal fixation of tibial plateau fractures, and to explore the biomechanical advantages of the personalized plate system with matching plate and optimized screw trajectories in the internal fixation of tibial plateau fractures. Schatzker classification I tibial plateau fractures were reconstructed using Unigraphics NX 8.5 software. Four groups of finite element models of Schatzker classification I tibial plateau fractures were simulated. Four kinds of implants were instrumented into the models, including the locking plate with mismatched anatomical shape and non-optimized screw trajectories (group A), the locking plate with mismatched anatomical shape but optimized screw trajectories (group B), the locking plate with matched anatomical shape but non-optimized screw trajectories (group C), and the locking plate with matched anatomical shape and optimized screw trajectories (group D). Loads of compression, rotation and varus-valgus were applied to a reference point coupled of the articular surface of tibial plateau. The biomechanical properties of different fixation methods contain deformation and stress index were compared to explore the influence of matching plate and optimized screw trajectories. As shown in the results, the three improved internal fixation groups (Group B, C and D) can effectively reduce the displacement of internal fixation and fracture end. Compared with group A, the reduction rates of deformation comprehensive index in group B, group C and group D were 0.94%, 0.22%, and 3.23%, respectively, the effect of reducing displacement in group D was the most obvious. On the contrary, the change rates of stress comprehensive index in the improved groups(Group B, C and D) were higher than group A, but the stresses increase were within the safe range. Compared with group A, the increase rates of stress comprehensive index in group B, group C and group D were 115.27%%, 32.77%, and 58.89%, respectively. The stress increase rate of group C was the lowest, followed by Group D. Base on the above results, we believe that matched plate and optimized screw trajectories group can obtain better fixation effect. Combined with the comprehensive stress and deformation index, it can be seen that the fixation effect is the best when plate matching and screw trajectories optimization for the Schatzker classification I tibial plateau fractures. And the influence of screw factor is more important than anatomical matching plate.