Biomechanics of posterior mono-segmental fixation for thoracolumbar fractures: a three-dimensional finite element analysis / 中华创伤杂志

ABSTRACT

Objective To establish a three-dimensional finite element model of thoracolumbar fractures treated by mono-segmental instrumentation in the fractured part for testing effect of such fixation mode on adjacent segments.Methods CT scanning data of T10-L2 were used to build a normal model at T10-L2 region,a fracture model at T12 segment as well as a mono-segment fixation or short-segment fixation model.Stress of discs and vertebral body adjacent to the fixed vertebrae were tested in axial compression,anteflexion,extention,lateroflexion,and axial rotation.Results The fracture model presented significant increase concerning stress of nucleus pulposus and annular fibrosus at T10-T11 segments and annular fibrosus at L1-L2 segments in anteflexion,extention,and lateroflexion when compared with the normal model.General raise range of the stress reached around 75％,but was dropped to 23％ after short-segment fixation and to 18％ after mono-segmental fixation.And again,stress of nucleus pulposus at L1-L2 segments was increased by 46％ or so,which was declined to 12％ after short-segment fixation and to 8％ after mono-segmental fixation.Stress at lower endplate of T10 and at upper endplate of L2 in the fracture model group were increased by 24％ and 43％ respectively when compared to the normal model,but both presented a notable drop after internal fixation.The latter was decreased to a level slightly higher than that of model group,namely 8％ more after short-segmental fixation and 4％ more after mono-segmental fixation; the former was decreased to a level even lower than that of control group,namely 2％ less after short-segmental fixation and 8％ less after mono-segmental fixation.Conclusion Mono-segmental fixation reduces adjacent disc stress in contrast to conventional short-segmental fixation and hence is an effective alternative treatment of monosegmental thoracolumbar fractures.