抄録
Lumbar interbody spacers used in posterior interbody fusion are made of titanium alloy which has a much higher elastic modulus than bone. Therefore, the induction of stress shielding may become a problem. In an effort to increase mechanical stimulus to the lumbar spine we propose changing the material of the spinal interbody fusion implant from a titanium alloy to plastic (PEEK - polyetheretherketone). We proposed using a spacer and casing rod made of PEEK and we conducted the following experiments to determine on effective design of spacer and casing rod. CAD data of the lumber spine (L4, L5) consisting of cortical bone and spongy bone, and the lumbar implant were created. FEM analyses were performed by varying the thickness of the spacer and the inner diameter of the casing rod with a load of 700N to simulate a standing position. We found a large amount of strain is applied to the interbody with the casing rod of 4mm inner diameter. Also excessive stress is observed in the spacer that has 2mm thickness. Therefore, a 2.5mm or 3mm spacer is advised. A future study will analyze flexed spinal positions.
