Design, production and biomechanical characterization of trabecular intervertical fusion cage from TI6AL4V alloy by additive manufacturing

The spine, which starts from the bottom of the head bones called cranium and continues until the coccyx, is composed of soft tissues and vertebrae, is an important part of the functional and complex body of the human body. The intervertebral disc which is part of the spine with a large mechanical and functional importance is subject to complex loads, with the combination of compression, bending and torsion during the daily activities. This structure has critical functions such as load distribution, load bearing and preventing excessive movement. Therefore, possible pathological changes in the intervertebral disc may cause dysfunction of the spine. In the treatment of spinal disorders and degenerative disc diseases, fusion surgery has become the standard treatment method. Intervertebral fusion cages are widely used in spinal surgery to restore disc space and maintain height and to provide fusion after discectomy. Parameters that to have high osseointegrasyon ability, good mechanical properties, high corrosion resistance and high wear resistance are important to select material of interbody fusion cages. In this thesis, additive manufacturing method, also known as three-dimensional printing, which is a new production technique and which has been widely used recently, has been used to increase osseointegrasyon, since bone o osseointegrasyon increases more bone implant interaction and stronger mechanical strength. The aim is to manufacture a porous intervertebral fusion cage, to reduce the elasticity modulus of titanium cages and to make the elastic properties closer to the natural bone tissue. In accordance with this purpose design, manufacturing and biomechanical characterization of the trabecular intervertebral fusion cage from Ti-6Al-4V alloy were performed by the additive manufacturing method in this thesis. A literature search was conducted to determine the optimum production parameters. As a result of the literature review, studies evaluating fatigue performance were not observed. The optimum production parameters of the intervertebral fusion cages to be produced by the additive manufacturing method were determined as a result of the mechanical, clinical studies and analysis. Direct metal laser sintering (DMLS) was chosen as the production technique. After production, heat treatment will be done. Different designs were created. The selected parameters were sent to the manufacturer to produce different designs. The static and dynamic performance of the intervertebral fusion cages with different designs are evaluated with biomechanical tests performed according to the relevant standards of ASTM. As a result, Ti-6Al-4V trabecular intervertebral fusion cage which has high biomechanical performance and osseointegrasyon capability has been developed with additive manufacturing method.