Introduction: Titanium(Ti) is indispensable because of its high mechanical reliability and good osteoformation for spinal surgery. On the other hand, it also has demerits: it often produces artifacts in taking radiological imaging and causes breakage of surrounding bones.
With the advance of recent technology, Ti can be transformed into sponge-like, porous metallic materials having a three-dimensional network structure, which is called " Ti foam". The elasticity is close to those of the cancellous bone. Due to its extreme high porosity, the resolution of the demerits and developing of merits might be expected. Objective of this study is biomechanical, histological and radiological evaluation of the Ti foam in osteoformation.
Methods: Two types of Ti foams, of which porosity was 80% and 90%, and Ti with 0% porosity as a control, were embedded in the femurs of 11 rabbits. Five rabbits were sacrificed at 4 weeks and others at 12 weeks after surgery. These femurs containing the Ti implants were harvested for analysis in osteoformation.
Results: In the biomechanical analysis, 80% porosity group was more effective in osteoformation. Significant difference in the push-out strengths existed between the control group and 80% porosity group at 4 weeks (p=0.048) and at 12 weeks after implant (p=0.001). In the histopathological analysis, good osteoformation was confirmed in 80% porosity group, leading to the same result to the biomechanical analysis. In the radiological analysis, the findings of osteoformation obtained from micro-computed tomography proved to be quite similar to the actual histopathological findings.
Conclusions: It is considered that Ti foam with 80% porosity, which overcomes the demerits of Ti, is superior in osteoformation from both histological and biomechanical viewpoints. Moreover, it is not influenced by radiological artifact. It is suggested that Ti foam can be an excellent biomaterial.
Patient Care: Recently, polyether ether ketone (PEEK), a polymer with high radiation permeability, has often been applied to spinal implants, because it can decrease the artifact in CT scan or MR imaging. However, recently, a case of breakage of a lumber spine implant made of PEEK was reported in FDA. According to the present study, Ti foam with 80% porosity, which overcomes the demerits of Ti used in a spinal implant, i.e., high Young's modulus and artifacts occurring in radiological imaging, is superior in osteoformation and bone fusion from both histological and mechanical viewpoints. We believe its clinical application needs to be promoted as an excellent biomaterial.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) consider that Ti foams, which overcome the demerits of Ti, is superior in osteoformation and bone fusion from both histological and mechanical viewpoints.