In Vivo Reconstruction of the Acetabular Bone Defect by the Individualized Three-Dimensional Printed Porous Augment in a Swine Model

Abstract

Background and Purpose. This study established an animal model of the acetabular bone defect in swine and evaluated the bone ingrowth, biomechanics, and matching degree of the individualized three-dimensional (3D) printed porous augment. Methods. As an acetabular bone defect model created in Bama miniswine, an augment individually fabricated by 3D print technique with Ti6Al4V powders was implanted to repair the defect. Nine swine were divided into three groups, including the immediate biomechanics group, 12-week biomechanics group, and 12-week histological group. The inner structural parameters of the 3D printed porous augment were measured by scanning electron microscopy (SEM), including porosity, pore size, and trabecular diameter. The matching degree between the postoperative augment and the designed augment was assessed by CT scanning and 3D reconstruction. In addition, biomechanical properties, such as stiffness, compressive strength, and the elastic modulus of the 3D printed porous augment, were measured by means of a mechanical testing machine. Moreover, bone ingrowth and implant osseointegration were histomorphometrically assessed. Results. In terms of the inner structural parameters of the 3D printed porous augment, the porosity was $55.48\pm 0.61\%$ , pore size $319.23\pm 25.05\mu \text{m}$ , and trabecular diameter $240.10\pm 23.50\mu \text{m}$ . Biomechanically, the stiffness was $21464.60\pm 1091.69\text{N}/\text{mm}$ , compressive strength $231.10\pm 11.77\text{MPa}$ , and elastic modulus $5.35\pm 0.23\text{GPa}$ , respectively. Furthermore, the matching extent between the postoperative augment and the designed one was up to $91.40\pm 2.83\%$ . Besides, the maximal shear strength of the 3D printed augment was $929.46\pm 295.99\text{N}$ immediately after implantation, whereas the strength was $1521.93\pm 98.38\text{N}$ 12 weeks after surgery ( $p=0.0302$ ). The bone mineral apposition rate (μm per day) 12 weeks post operation was $3.77\pm 0.93\mu \text{m}/\text{d}$ . The percentage bone volume of new bone was $22.30\pm 4.51\%$ 12 weeks after surgery. Conclusion. The 3D printed porous Ti6Al4V augment designed in this study was well biocompatible with bone tissue, possessed proper biomechanical features, and was anatomically well matched with the defect bone. Therefore, the 3D printed porous Ti6Al4V augment possesses great potential as an alternative for individualized treatment of severe acetabular bone defects.