Biomechanical evaluation of interbody devices by using mechanical compressive test: PEEK spacers versus PMMA cement spacers

Abstract

If spine degenerations are accompanied by osteoporosis, the traditional PEEK spacers can strongly subside into the irregularly deformed endplates and vertebrae following surgical stabilization. To avoid implant subsidence, a new technique is developed where bone cement is applied as interbody device along the vertebra-implant interface. In this study, the mechanical comparison of the traditional PEEK and the new PMMA cement spacers are presented based on uniaxial compression tests. It was concluded that in osteoporotic spine the cement spacers provide better contact along the irregularly deformed endplates, and stronger vertebra-implant interface leading to enhanced stability of lumbar interbody fixation. In the case of PMMA cages, the failure deformation of segments is almost the half of that of the PEEK spacers, while the stiffness of them is more than two times larger. In strongly osteoporotic cases, a more evenly distributed cement pattern results in smaller stress concentrations and greater strength which may decrease the risk of subsidence. DOI: 10.17489/biohun/2013/1/28