BACKGROUND:Transforaminal lumbar interbody fusion(TLIF)can be applied in any lumbar segment,and retain integrity of lateral vertebral plate and zygapophysiai joints.However,few studies have been conducted about the biomechanical performance.OBJECTIVE:To explore the stability of lumbar intervertebral segment following TLIF appHed bilateral and unilateral transpedicular screws fixation.DESIGN,TIME AND SETTING:Biomechanical test was performed at the Institute of Biomechanics,Shanghai University and Nantong University between August 2005 and April 2006.MATERIALS:Twenty samples of fresh one-month-old calf lumbar vertebra.METHODS:Twenty samples of calf lumbar vertebra underwent TLIF alone,TLIF in combination with bilateral or unilateral transpedicular screws fixation.Biomechanical test was performed on spinal three dimensional motion testing machine.MAIN OUTCOME MEASURES:Stress,displacement.strain and torsion angle were recorded.RESULTS:After TLIF without fixation.no obvious changes were found in mean stress and strain,but the axes stiffness and rotational stiffness were significantly decreased,indicating TLIF could produce immediate lumbar stability.After TLIF with unilateral or bilateral transpedicular screws fixation,the lumbar stability was significantly enhanced compared with TLIF alone,especially bilateral transpedicular screws fixadon.Although the lumbar stability following unilateral transpedicular screws fixation was inferior to bilateral fixation,it was still greatly enhanced,even bxceeded normal sample,indicating TLIF with unilateral transpedicular screws fixation could produce enough initiallumbar stability.CONCLUSION:TLIF alone cannot support sufficient initial stability,but TLIF with bilateral and unilateral transpedicular screws fixation can enhance lumbar initial stability.