Young Kim
The Journal of Mechanical Science and Technology, vol. 23, no. 1, pp.36-44, 2009

Abstract : Cage subsidence and loosening increase with a decrease of bone density. Thus, the stabilization of spinal segments may be dependent on density of cancellous bone. The aim of this study was to investigate the effects of bone density on the biomechanical behavior of the ALIF with cylindrical cages and PSF. Nonlinear numerical analysis was carried out by means of finite element method, and various Young’s moduli those have been described by the bone density were employed for the calculation. The range of motion was increased by 120% with decreasing of the density. Relative slip distance increased by 810% at the bone-cage interface and by 1750% at the bone-screw interface with a decrease of the density. Continuous cage subsidence, cage loosening, screw loosening and screw failure would occur particularly during an excessive flexion and/or an excessive axial rotation. The excessive low density would mainly cause pediclescrew loosening due to the remarkable screw slip. In the case of excessively reduced density, therefore, further study is required in order to investigate how to improve the current PSF for the segmental stability.

Keyword : ALIF; PSF; Cylindrical cage; Bone stress; Relative slip