BIOMECHANICAL STUDY ON ADJACENT UPPER AND LOWER AND UNILATERAL FRACTURED VERTEBRAL PEDICLE SCREW FIXATION IN TREATMENT OF THORACOLUMBAR FRACTURE

Abstract

To investigate the stability of unilateral fractured vertebral pedicle screw fixation in the treatment of thoracolumbar fracture. Eighteen fresh calf thoracolumbar spine specimens (T11-L3) were obtained to establish the L1 burst fracture models with Panjabi's high speed trauma apparatus, and were divided into 3 groups:pedicle fixation for adjacent upper and lower vertebrae of fractured vertebra (4 pedicle screws in group A), combined with pedicle screw fixation for unilateral fractured vertebrae (5 pedicle screws in group B), and three-level 6 pedicle fixation (group C). Under normal, fractured, and reconstructed conditions, the range of motion (ROM) of adjacent upper and lower vertebrae of fractured vertebra were measured in flexion, extension, bilateral bending, and axial rotation. Axial stiffness under flexion-compression was measured on the MTS-858 testing system. There was no significant difference in ROM and axial stiffness under normal and fractured conditions in all directions among groups (P<0.05), indicating load balance in the groups. ROM of groups B and C were significantly less than that of group A under reconstructed condition in all directions (P<0.05), but no significant difference was found between group B and group C (P>0.05). Biomechanical test showed that group B was significantly higher than group A in the axial stiffness value (P<0.05), but difference was not significant between group B and group C (P>0.05). Transpedicular fixation of fractured vertebrae can enhance the stability of the spine. Both unilateral and bilateral fractured vertebral pedicle screw fixations have the same stability.