Finite element analyses of unilateral and bilateral pedicle screw fixation plus interbody fusion in lumbar spine
WANG Peng， WANG Jian， HU Yong， CHENG Hai-feng， JIAO Pei-feng， ZHANG Mei-chao
Chinese Journal of Clinical Anatomy ›› 2016, Vol. 34 ›› Issue (3) : 331-337.
Finite element analyses of unilateral and bilateral pedicle screw fixation plus interbody fusion in lumbar spine
Objective To analyze biomechanical characteristics of pedicle screws and lumbar under different pressure loads between unilateral and bilateral pedicle screw fixation plus interbody fusion after discectomy by creating a normal L4~5 spinal segment finite element model. Methods A three-dimensional finite element model was created by using CT sectional images of an intact L4~5 segment of a healthy male and then model A and model B were established. Model A was unilateral pedicle screw fixation plus interbody fusion after lumbar discectomy, and model B was bilateral pedicle screw fixation plus interbody fusion after lumbar discectomy. The lumbar variation, the changes of lumbar stress and the apex stress of pedicle screw under flexion, extension, left/right lateral bending and left/right rotation were observed in the two models. Results The maximum displacement and stress of pedicle screws in model A reached max under the operating models of fixed-side flexion，and the maximum stress of lumbar reached max under extension. While in model B the maximum displacement reached max under extension,and the maximum stress of screws and lumbar reached max under rotation. There was significant difference between model A and B under fixed-side flexion and extension. Conclusion Compared with bilateral and unilateral fixation plus fusion, the possible potential risk of instability, screw loosening and metal breakage of unilateral fixation plus fusion was greatly increased. The movement of extension, fixed-side flexion and rotation should be reduced before bone union after unilateral fixation plus fusion.
Lumbar / Bilateral pedicle screw fixation / Unilateral pedicle screw fixation / Stress / Finite element model
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