Nowadays the need for faster development cycle can be found all over in the industry. Rapid prototyping has become a common tool in product development, but available materials in these technologies can not always substitute the materials needed for product. Rapid tooling makes it possible to produce a small series of a product with the same technology and materials as that of the final product. In our work we have used the Polyjet technology (Objet Geometries Ltd.) to produce mold for the injection molding of biodegradable interference screws. Our goal was to produce enough quantity of interference screws for biomechanical measurements, with a technology that is more cost efficient than selective laser sintering (SLS). Two types of mold materials were tested. The first mold was prepared from Fullcure720, an acrylic based, UV curing resin on an Object ALARIS machine. The second mold was prepared with resin casting from AH-12/T-58 (100:40) epoxy resin filled with 25 m% Al2O3 powder. For injection molding Natureworks 3051D polylactide (PLA) was used. After injection molding the weight and the geometry of the screws were measured. The results showed that the molds can withstand 5-10 injection cycles, and the screws manufactured meet the requirements for biomechanical tests on porcine knees.
Multiple techniques for the reconstruction of anterior cruciate ligament (ACL) are available, most of which use implant made from metallic or bioabsorbable materials. Currently one of the most widely used fi xation methods for anterior cruciate ligament reconstruction with bone tendonbone graft is the interference screw. The aim of our work was to test custom design screw geometry, whether it is appropriate for ACL reconstruction. New screw was designed geometry for the work, so that screws with the same geometry could be produced for later work, from different materials. In this study injection molded biodegradable interference screws were tested on porcine femurs, with bone-patellar tendon-bone (BPTB) graft fi xation. The average failure load and the stiffness (772 ± 225 N and 109 ± 33.9 N/mm respectively) of the fi xation was higher than literature average, although within standard deviation. Test results showed that the designed screw geometry is adequate for BPTB graft fi xation.
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