The hydroxyapatite modified 3D printed poly L-lactic acid porous screw in reconstruction of anterior cruciate ligament of rabbit knee joint: a histological and biomechanical study

Abstract

Abstract Background 3D printing technology has become a research hotspot in the field of scientific research because of its personalized customization, maneuverability and the ability to achieve multiple material fabrication. The focus of this study is to use 3D printing technology to to customize personalized orthopedic endosseous implant porous screws and to explore its effect on tendon-bone healing after anterior cruciate ligament (ACL)reconstruction. Methods The poly L-lactic acid (PLLA) porous screws which meet the requirements of the experiment are prepared by 3D printing technology. The hydroxyapatite (HA) was adsorbed on porous screws by electrostatic layer-by-layer self-assembly (ELSA) technology, and PLLA-HA porous screws were prepared.Scanning electron microscope (SEM) was used to observe the surface morphology of scaffolds before and after modification. Determination of porosity of screw support by liquid replacement method. The PLLA group was fixed with PLLA porous screw and the PLLA-HA group was fixed with PLLA-HA porous screw. Histology, imaging and biomechanics were observed at 6 and 12 weeks after operation. Results The PLLA porous screws prepared by 3D printer meet the design requirements, and the voids in the stents are evenly distributed and connected with each other. After surface modification, HA was uniformly distributed in PLLA screw scaffolds. Histology showed that compared with PLLA group, mature bone trabeculae were integrated with grafted tendons in PLLA-HA group. Micro-CT showed that the bone formation index of PLLA-HA group was better than that of PLLA group. The new bone was uniformly distributed in the bone tunnel along the screw channel. Biomechanical experiments showed that the failure load and stiffness of PLLA-HA group were significantly higher than those of PLLA group. Conclusions HA modified 3D printed porous screw can not only fix the transplanted tendon, but also effectively increase the new bone mass in the bone tunnel and promote the bone integration at the tendon-bone interface by promoting the bone growth in the bone tunnel.3D printed PLLA-HA porous screws are likely to be used in clinic in the future.3D printed PLLA-HA porous screws are likely to be used in clinic in the future.