A biomechanical study of effects of anterior cervical screw sagittal angle on adjacent segments
LU Zhao-hua
ZHAO Feng
SU Wei-cheng
ZHAO Xiao-yong
ZHAO Yan-tao
LI Zhong-hai
Abstract：Objective To analyze effects of different screw sagittal angles ( SSA ) on the stress of adjacent levels, and determine whether SSA is a risk factor of adjacent segment disease ( ASD ).Methods A three-dimensional ifnite element ( FE ) model of intact C3-7 segments was developed and validated based on healthy males. C5 anterior corpectomy and allograft interbody fusion with a rigid anterior screw-plate construction was created from C4 to C6. Three additional FE models were developed from the fusion model corresponding to 3 different combinations of SSA: ( 0°, 0° ), ( 5°, 5° ), and ( 10°, 10° ). Von Mises stress on the C4 superior end-plate, C6 inferior end-plate and screw-plate were analyzed.Results The largest stress appeared when the superior end-plate of C4 was in lfexion position in the front area. With the increase of SSA, the peak stress was gradually reduced. When the SSA was increased by 10°, the peak stress was reduced by 12.67%. The largest stress appeared when the lower end-plate of C6 was in lfexion position in the front area. With the increase of SSA, the peak stress was gradually reduced. When the SSA was increased by 10°, the peak stress was reduced by 7.99%. The peak stress was noticed in the middle area when the plate was in lfexion and extension position, which was signiifcantly larger than that in the upper and lower area. With the increase of SSA, the stress would be gradually raised.Conclusions Larger SSA produces greater stress of the screw plate and lower stress of the end-plate in adjacent segments, reducing the incidence of ASD.
Keywords：Cervical vertebraeInternal ifxatorsFinite element analysisBiomechanicsSagittal screw angle
Publication Date：2015-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：5( 617-621 )