ABSTRACT
BACKGROUND: Treatment strategy for vertebral burst fracture remains controversial because of its complex morphological changes. There is a lack of knowledge concerning the fixation of thoracolumbar burst fracture (A3.3 by AO classification). OBJECTIVE: To investigate the biomechanical characteristics of thoracolumbar burst fracture (A3.3 by AO classification) after screw fixation, thereby providing reference for choosing an appropriate placement method. METHODS: (1) Three-dimensional motion test: the samples were divided into complete set (group A), L1burst fracture (A3.3 by AO classification) (group B), trans-vertebral fixation (group C), screw fixation at the unilateral fracture level (group D), screw fixation at the bilateral fracture levels (group E), and screw fixation at the bilateral upper fracture levels (F). Several swine spinal specimens served as group A, L1was modeled into A3.3 by AO classification fracture after three-dimensional motion. (2) The compressive stiffness test: one fresh specimen served as complete group (group A), B, C, D, E, and F groups underwent compressive stiffness test. RESULTS AND CONCLUSION: (1) Three-dimensional motion tests: the range of motion in the group B was significantly decreased after C, D, E, and F fixations (P < 0.05). Compared with groups C, D and E, the range of motion at the directions of anteflexion, left flexion, right flexion, left and right rotation in the group F was significantly increased in the group F (P < 0.05); the range of motion in the groups E and D was significantly smaller than that in the groups C and F (P< 0.05); there was no significant difference between groups D and E (P > 0.05). (2) The stiffness in the other groups was significantly higher than that in the group B, especially group E, and the groups D and A did not differ significantly. (3) These results indicate that the fixation at the unilateral fracture level and bilateral fracture levels both can significantly improve the stability of thoracolumbar burst fracture (A3.3 by AO classification), and the former can reduce the economical burden and placement complications.