Homogenous scaffold-based cranial/skull implant modelling and structural analysis—unit cell algorithm-meshless approach

Research on a novel flexible bionic artificial anal sphincter

BACKGROUND

Artificial anal sphincter is a novel method for the treatment of fecal incontinence. Aiming at the problems of complex mechanical structure, high mechanical failure rate, large volume and poor biocompatibility of existing artificial anal sphincters, this article proposes a novel flexible artificial anal sphincter with bionic structure.

METHODS

A novel flexible artificial anal sphincter was proposed with bionic structure by analogy with the puborectalis, flexible transmission by flexible tendons, good biocompatibility by using thermoplastic urethane and medical silicone, small size and lightweight. The interaction between the rectum and the artificial anal sphincter is simulated by the finite element analysis, and the changes of the anorectal angle and the stress during the traction process of the rectum are analyzed.

RESULTS

The results suggest that the formed anorectal angle of <90° may effectively control defecation, so the effectiveness of the artificial anal sphincter is preliminarily verified. When the traction angle was 71° and the intestinal tube was basically closed, the maximum equivalent stress was 148.45 kPa, the maximum and minimum principal stress were 88.37 and 82.74 kPa, which were all below the safety pressure that initially verified the safety of the artificial anal sphincter.

CONCLUSION

The novel flexible artificial anal sphincter may effectively reduce the stress between the device and the rectum and improve the biomechanical compatibility.

3D-Printed Flat-Bone-Mimetic Bioceramic Scaffolds for Cranial Restoration

The limitations of autologous bone grafts necessitate the development of advanced biomimetic biomaterials for efficient cranial defect restoration. The cranial bones are typical flat bones with sandwich structures, consisting of a diploe in the middle region and 2 outer compact tables. In this study, we originally developed 2 types of flat-bone-mimetic β-tricalcium phosphate bioceramic scaffolds (Gyr-Comp and Gyr-Tub) by high-precision vat-photopolymerization-based 3-dimensional printing. Both scaffolds had 2 outer layers and an inner layer with gyroid pores mimicking the diploe structure. The outer layers of Gyr-Comp scaffolds simulated the low porosity of outer tables, while those of Gyr-Tub scaffolds mimicked the tubular pore structure in the tables of flat bones. The Gyr-Comp and Gyr-Tub scaffolds possessed higher compressive strength and noticeably promoted in vitro cell proliferation, osteogenic differentiation, and angiogenic activities compared with conventional scaffolds with cross-hatch structures. After implantation into rabbit cranial defects for 12 weeks, Gyr-Tub achieved the best repairing effects by accelerating the generation of bone tissues and blood vessels. This work provides an advanced strategy to prepare biomimetic biomaterials that fit the structural and functional needs of efficacious bone regeneration.