The designs and feasibility of clinical applications about a novel percutaneous pedicle screw system

Abstract

Objective To evaluate the rationality of the designs and the feasibility of applications about a novel percutaneous pedicle screw system. Methods Six human cadaver specimens were used to simulate operative procedures with the novel percutaneous pedicle screw system (group A), and Sextant sys-tem was served as a control group (group B). Compression fractured vertebral bodies harvested from fresh calf were distracted with novel percutaneous pedicle screw system to assess the distraction function of percuta-neous system and distraction effect of modified screw. Biomechanical properties of modified screw were as-sessed according to the fixation effects of three types of screw-rod systems for fractured segment. Results The mean operation time in group A [(38.2 6.20) min] and B [(56.4 12.8) min] had significant difference (P< 0.05). The excellent and good rate of screws position was 91.7% and 95.8% in group A and B, respectively, showed no significant difference. The novel percutaneous system had a good distraction function to three kinds of screws. Modified and monoaxial screws could distract mainly the anterior column of vertebral body and there was no significant difference. However, the polyaxial screws distracted mainly middle and posterior column, the distraction effect of the anterior column was not as good as previous screws (P<0.05). There were no significant differences in flexion and extension, lateral bending and rotation of all specimens in intact and fractured. Modified and monoaxial screws could provide similar three-dimensional stabilities to fractured specimens. Polyaxial screw provided poor stability in flexion and extension compared with the two previous of screws (P<0.05). There were no significant differences in lateral and rotation stability provided by three kinds of screws. Conclusion Through using novel percutaneous pedicle screw system, modified and monoaxial screws have similar distraction effect on anterior column of vertebral body, and can provide similar three-dimen-sional stability. The novel percutaneous pedicle screw system is well-designed and feasible in clinical practice. Key words: Spine; Biomechanics; Internal fixators; Bone screws