Abstract
Introduction
Expandable anterolateral plates facilitate the reduction of posttraumatic deformities of thoracolumbar spine injuries and are commonly used in cases of unstable injuries or compromised bone quality. In this human cadaver study, the craniocaudal yield load of the bony fixation of an anterior angle stable plating system and the influence of Polymethyl Methacrylate (PMMA) augmentation on the primary stability of the screw–bone interface during kyphosis reduction was evaluated in twelve osteoporotic thoracolumbar vertebrae.
Material and Methods
The anterolateral stabilization device used for this study is comprised of two swiveling flanges and an expandable midsection. It facilitates the controlled reduction of kyphotic deformities in situ with a geared distractor. Single flanges were attached to twelve thoracolumbar vertebrae. Six specimens were augmented with PMMA by means of cannulated bone screws. The constructs were subjected to static, displacement controlled craniocaudal loading to failure in a servohydraulic testing machine.
Results
The uncemented screws cut out at a mean of 393 +/− 66 N, whereas the cemented screws demonstrated significantly higher yield load of 966 +/− 166 N (p < 0.02). No significant correlation between bone mineral density and yield load was detected in this setting.
Conclusion
The results of this study indicate that PMMA augmentation is an effective method to increase two- to 3-fold the primary stability of the screw–bone interface of an anterolateral spine stabilization system in osteoporotic bone. We recommend the system in cases of severely compromised bone quality to reduce the risk of screw loosening during initial kyphosis correction and to increase long-term construct stability.