369Fabrication of 3D gel-printed ß-tricalcium phosphate/titanium dioxide porous scaffolds for cancellous bone tissue engineering.

Human bone is composed of cortical bone and cancellous bone. The interior portion of natural bone is cancellous with a porosity of 50%-90%, but the outer layer is made of dense cortical bone, of which porosity was not higher than 10%. Porous ceramics were expected to be research hotspot in bone tissue engineering by virtue of their similarity to the mineral constituent and physiological structure of human bone. However, it is challenging to utilize conventional manufacturing methods to fabricate porous structures with precise shapes and pore sizes. Three-dimensional (3D) printing of ceramics is currently the latest research trend because it has many advantages in the fabrication of porous scaffolds, which can meet the requirements of cancellous bone strength, arbitrarily complex shapes, and individualized design. In this study, ß-tricalcium phosphate (ß-TCP)/titanium dioxide (TiO2) porous ceramics scaffolds were fabricated by 3D gel-printing sintering for the first time. The chemical constituent, microstructure, and mechanical properties of the 3D-printed scaffolds were characterized. After sintering, a uniform porous structure with appropriate porosity and pore sizes was observed. Besides, biological mineralization activity and biocompatibility were evaluated by in vitro cell assay. The results demonstrated that the incorporation of TiO2 (5 wt%) significantly improved the compressive strength of the scaffolds, with an increase of 283%. Additionally, the in vitro results showed that the ß-TCP/TiO2 scaffold had no toxicity. Meanwhile, the adhesion and proliferation of MC3T3-E1 cells on scaffolds were desirable, revealing that the ß-TCP/TiO2 scaffolds can be used as a promising candidate for repair scaffolding in orthopedics and traumatology.

Automatic recognition of pertrochanteric bone fractures in femur using level sets.

Femur fracture is one of the common diseases in the elderly. In this paper, an automatic and efficient classification method of femoral pertrochanteric fractures is proposed based on image segmentation techniques. The types of femoral pertrochanteric fracture are defined firstly according to the difference of fracture parts. To reduce the computational complexity, only four directions images are used in each 3D femur, i.e. the anterior, the anterolateral, the posterior and the posterolateral images of a femur. And then those fracture images are segmented from background using level set method. Considering the numerical errors and the instability of evolution in conventional level set formulations, a distance regularization term and an external energy constraint term are used, which are able to maintain a desired shape of the level set function and speed up the motion of the zero level contour in evolution process. After segmentation, the Canny edge detector is used to extract the fracture edges on femur. The types of femoral pertrochanteric fracture are classified by comparing the difference of edges between reference normal images and the testing images. Except the given four directions of 3D image, the classification is processed automatically. Experimental results illustrated the effectiveness of the proposed method.