The Effect of Temperature on Pedicle Screw Pullout Strength: A Biomechanical Analysis in a Validated Biomimetic Spine Model

- Robby Turk , Austin Allen, Rebecca DeCarlo


Pedicle screw loosening is a relatively common complication following posterior spinal fusion. The purpose of this study was to evaluate the impact of screw temperature at time of placement on pullout strength. The authors hypothesized that screws placed at chilled temperatures should undergo thermal expansion as they returned to room temperature and should subsequently have improved pullout strength. Screws were placed into a 3D printed biomimetic lumbar 4 pedicle in groups of ten at the Carolina Neurosurgery and Spine biomechanics lab. This study assessed screws placed at room temperature (20.72°C), heated screws (47.72°C), and chilled screws (2.91°C). All screws were allowed to return to room temperature and then forcibly removed under constant force and distance monitoring to assess break point. The mean insertional torque was 62.9Ncm, 90.95Ncm, 45.47Ncm for the control, frozen and heated screw groups, respectively (p<0.05). This suggest that pullout force of pedicle screws was not significantly impacted by temperature of screw insertion at the temperatures tested in this biomechanical model.