In this article, research trend of biomaterials for spinal fusion was summarized with an emphasis on hydroxyapatite (HA), titanium(Ti), and polyetheretherketone (PEEK) as representatives of ceramics, metals, and polymers, respectively. Ceramic materials represented by HA are highly biocompatible but have low strength and fracture toughness, so there has been much effort to improve these mechanical properties. Metals such as titanium, Ti, are mechanically strong but have a drawback of stress shielding effect, which can be avoided by fabricating into porous body. Also there have been many researches to improve the biocompatibility of PEEK, which has been widely used recently as a substitute to Ti.
