The Evaluation of a Novel Three-Dimensional Printed Expandable Pedicle Screw Sleeve Insert

When used in combination with decompression, spinal fusion is a successful procedure for treating patients with spinal stenosis and degenerative spondylolisthesis. While a number of auxiliary devices have been proposed to enhance the fixation of the screw within the pedicle and vertebral body, there is conflicting information regarding the efficacy of their use. Therefore, the aim of this study was to determine the ability of a novel expandable pedicle screw to improve the fixation of the pedicle screw within the pedicle and vertebral body. A three-dimensional (3D) printed, screw sleeve was designed that expanded within the pedicle and vertebral body when a standard pedicle screw was inserted into it. The left and right pedicle of ten (N = 10) cadaveric lumbar spine specimens (L3-L5) were randomly assigned to be instrumented with either a pedicle screw and the sleeve or a pedicle screw only. Following instrumentation, the screws were exposed to tensile load at 5 mm/min until failure. The failure force, failure deformation, and area under the force-deformation curve were determined and compared between screw conditions. There were no significant differences between the screws and sleeve, and the screw only conditions for the failure force (p = 0.24), failure displacement (p = 0.10), and area under the curve (p =038). While the novel screw sleeve presented here performed as well as a screw without a sleeve, it was better than other screw augmentation devices reported previously. In addition, it is likely that this device would prove useful as an enhancement to revision.