Finite element analysis of thoracolumbar fracture following varying fixations

Yuanjin SONG; Jinfang CAI

ABSTRACT

BACKGROUND:

A selection of treatment for thoracolumbar fracture is very important.

OBJECTIVE:

To develop and validate three-dimensional finite element models of human thoracolumbar fracture using varying fixation methods,and to compare biomechanical characteristics of fixation method.DESIGN TIME AND

SETTING:

A contrast observation was performed at the Mechanical Experiment Center of Tongji University from August to October 2008.MATERIALS64-slice spiral CT (Siemens,Germany) was used to scan T_(11)-L_1 segments of an adult male,and the slice thickness was 0.6 mm.based on Boolean operation,the lower half of T_(12) segment was resected,and the structure of posterior part was reserved to establish finite element model of thoracolumbar fracture.

METHODS:

There were five groups in this study,including 4 pedicle screws+2 rods (group 1),5 pedicle screws+2 rods at one side (group 2),6 pedicle screws+2 rods at both sides (group 3),anterior fixation (group 4),and anterior plus posterior fixation (group 5).Forces of axial compressive,anterior bending,posterior extension,left bending,and right rotation were loaded to compare the biochemical characteristics.MAIN OUTCOM

MEASURES:

vonMises stress and displacement at different directions.

RESULTS:

The stresses of all the fixation screws increased from the anterior part to posterior part in all movement tests,and the strongest stress was measured in the joint position.The stress of proximal screw was stronger than that of the distal screw.Additionally,the stress in group 1 was significantly stronger than in groups 2,3,and 5 (P<0.01).The group 5 was the most stable,but the group 1 was the poorest.

CONCLUSION:

T_(12) bursting fracture models were established using varying fixation methods,and the results verified that short segment plus fracture vertebral segmental fixation has more superior biomechanics.