Biomechanical characteristics of placement methods of the thoracic pedicle screw system / 中国组织工程研究

ABSTRACT

BACKGROUND:Studies have shown that placement, needling point, angle and length of pedicle screws for thoracic vertebral fractures have been unified. Many studies concerned axial pul-out force and biomechanical behavior of a single screw, but few reports addressed the biomechanical behavior after the replacement with three kinds of screw connecting to rods. OBJECTIVE:To further observe and compare biomechanical behavior after three kinds of thoracic screw placement connecting rod using biomechanical testing, to understand the strength of thoracic pedicle screw replacement connecting rods, and the effects of its puling out on the stress of the bone surrounding the placement site. METHODS:The fresh frozen specimens of thoracic vertebra were divided into three groups at random the pedicle fixation group, the transverse process-vertebral body fixation group, and modified rib transverse process fixation group. Thoracic pedicle screw system was inserted by the standard placement method in each group. The experiment was measured on the mechanical equipment. During puling out, the strength that bone bore was described with dynamic curve, folowed by statistical analysis. The difference in the gripping force on the thoracic vertebra among three kinds of screw placement method was compared. RESULTS AND CONCLUSION: Among three kinds of screw placement methods and among three kinds of screw placement methods on the injured vertebral body, the gripping force was significantly bigger in the pedicle fixation group than in the transverse process-vertebral body fixation group and modified rib transverse process fixation group (P < 0.01). No significant difference in the gripping force was detected between the transverse process-vertebral body fixation group and modified rib transverse process fixation group. Results verified that the stability of loading ability was apparently better in the pedicle fixation group compared with the transverse process-vertebral body fixation group and modified rib transverse process fixation group.