Vertebrae, artificial

The cardiac pump theory states that the active compression of the heart between the sternum and vertebrae creates an artificial systole in which intraventricular pressure increases, the atrioventricular valves... 

The cardiac pump theory states that the active compression of the heart between the sternum and vertebrae creates an artificial systole in which intraventricular pressure increases, the atrioventricular valves close, the aortic valve opens, and blood is forced out of the ventricles. When ventricular compression ends, the decline in intraventricular pressure causes the mitral and tricuspid valves to open, and ventricular fining begins. 

The concept for artificial discs first appeared in the 1960s (Femstrom 1966) with the use of steel and vitallium balls implanted in intervertebral spaces. Unfortunately, this design was not successful because these balls penetrated through the endplates and the vertebrae eventually fused. Despite this undesirable consequence, research and development in the area of TDRs has continued since then. 

FIGURE 14.1.9 X-ray photograph of artificial vertebra of glass-ceramic A-W which substituted for a lumbar vertebra of a sheep and bonded to the surrounding cancellous bone (2 years after implantation photograph courtesy of Professor T. Yamamuro, Kyoto University, Japan). 

The advantages provided by the combination of bioactivity and specific mechanical properties (Table 4-13), such as compressive strength and fracture toughness, are evidenced by the successful application of glass-ceramics as artificial vertebrae (Fig. 4-26). The CERABONE A-W (1992) brochure presents a particularly effective example of how the material is used. The broken lumbar 2 vertebra in a 57-year-old patient was replaced by an implant made of CERABONE A-W glass-ceramic. The implant was held in place with a Kaneda device. The X-ray examinations conducted three and six years... 

Rgure 4-26 Artificial vertebrae, spacers, and fillers of CERABONE A-W. 

Due to its good properties of biocompatibility, bioactivity and mechanical properties glass-ceramics A/W is used from the Eighties, for the reconstructions of the iliac crests, artificial vertebrae, intervertebral discs. Glass-ceramics A/W can easily machined into various shapes using discs and reels of diamond, even into screws and in powder form can be used to repair and fill bone defects. 

Denozie G, David N. (2006) Biomechanical comparison between fusion of two vertebrae and implantation of an artificial intervertebral disc. Journal of Biomechanics 39 (2006) 766-775... 

A/W glass ceramic 1080 MPa Artificial vertebrae, Bone fillers, Intervertebral discs 129,130... 

Polymers have fonnd application in medical devices due to a combination of mechanical properties, ability to withstand the environment of the body, and also inertness relative to the body. Polymers and composites have been used as heart stents and valves, artificial joints, replacement vertebrae, bones, and so on. 

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