Biomechanical properties of a novel pourable cement pedicle screw and its application to osteoporotic lumbar degeneration

Liu Yang; Liu Dan; Xiao Yun-xiang; Chen Hai-dan; Zhao Hong-wei

doi:10.3969/j.issn.2095-4344.2016.31.016

Abstract：BACKGROUND:Fragile bone in senile osteoporosis patients easily weakened pedicle screw fixation capacity. Therefore, bone cement leakage and screw removal cannot be solved during pedicle screw repair in osteoporotic patients with degenerative lumbar spine. OBJECTIVE:To investigate the biomechanical properties of novel pourable pedicle screws and bone cement application effect in osteoporotic patients with degenerative lumbar spine. METHODS:Six lumbar specimens (T11-L5) at the mean age of (72.9±4.2) years were selected, total y 42 vertebrae. The average bone density was 0.696 g/cm2. Any side of al vertebrae was inserted with pourable pedicle screws. 2 mL of bone cement was perfused under the X-ray fluoroscopy with cement push rod and fil ing cylinder. The same number of conventional screws was inserted into the opposite side of the samples. Three-point bending test was performed in two kinds of screws. The maximum vertebral axial pul out force test and the maximum spin torque test were conducted in vertebra to observe the destruction of the vertebral body and implanted effect. RESULTS AND CONCLUSION:(1) The ultimate strength and yield load of novel pourable cement pedicle screws were significantly more than conventional screws (P<0.05). Ultimate displacement and yield displacement were significantly less in novel pourable cement pedicle screws than in conventional screws (P<0.05). (2) The maximum vertebral axial pul out force and the maximum spin torque were significantly higher in novel pourable pedicle screws than in conventional screws (P<0.05). (3) In summary, novel pourable cement pedicle screw is simple to operate, can effectively control bone cement penetration, and improve screw stability in osteoporotic vertebrae. Moreover, after treatment, the removal of screws is convenient, cannot evidently destroy vertebral body or screw channel, and promote early recovery.