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


BACKGROUND
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 or 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.
Mermelstein
L E
LE
Department of Orthopaedic Surgery, University of California, Davis, Sacramento, USA.
McLain
R F
RF
Yerby
S A
SA
D001672:Biocompatible Materials / Q000627:therapeutic use*; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use*; D001863:Bone Screws; D002102:Cadaver; D017886:Durapatite / Q000627:therapeutic use*; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D016103:Spinal Fractures / Q000601:surgery*; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000601:surgery*
D001672:Biocompatible Materials; D001843:Bone Cements; D017886:Durapatite