Reinforcement of thoracolumbar burst fractures with calcium phosphate cement - A biomechanical study

Study Design. A biomechanical study on the stabilization of thoracolumbar burst Fractures. Objective. To demonstrate that the addition of a calcium phosphate cement into the fractured vertebral body through a transpedicular approach is a feasible technique that improves the stiffness of a transpedicular screw construct. Summary of background Data. Short segment pedicle screw instrumentation is a commonly used method for reduction and stabilization of unstable burst fractures. Recent investigators, however, have reported a high rate of instrumentation failure and sagittal collapse when there is a loss of anterior column support. In this study, the ability of a new hydroxyapatite cement to augment anterior column support was investigated in a burst fracture model. Methods. A cadaveric L1 burst fracture model was stabilized using short segment pedicle screw instrumentation. Specially instrumented pedicle screws recorded screw-bending moments. The L1 vertebral body was reinforced with the hydroxyapatite cement through a transpedicular approach. Mechanical testing of the instrumented and instrumented-reinforced constructs were performed in flexion, extension, side bending, and torsion. Construct stiffness and screw-bending moments were recorded. Results. Transpedicular vertebral body reconstruction with hydroxyapatite cement reduced pedicle screw-bending moments by 59% in flexion and 38% in extension. Mean initial stiffness in the flexion, extension plane was increased by 40% (P<0.05). There were no statistically significant differences in these parameters with lateral bending to torsional movements. Conclusions. This hydroxyapatite cement compound augments anterior column stability in a burst fracture model. This technique may improve outcomes in burst fracture patients without the need for a secondary anterior approach.