Article
PMMA-augmented SI screw: a biomechanical analysis of stiffness and pull-out force in a matched paired human cadaver model
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Published: | October 5, 2015 |
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Background: Recent studies showed the potential advantage of cement-augmented SI screws compared to conventional non-augmented once with regard to pain relief and earlier recurrence of mobility.
The aim of this study was to assess the biomechanical performance of cement-augmented versus non-augmented SI screws in a human cadaveric pelvis model. We hypothesized that a cemented SI screw can carry higher loads than a non-augmented SI screw giving the patient the opportunity to start with full weight bearing sooner after the operationes. This is the first biomechanical study where cement-augmented SI screws were tested on human cadaver pelvises.
Material and Methods: Six human cadaveric pelvises preserved with the method of Thiel were used in this study. Each pelvis was split to a pair of 2 semi-pelves, assigned to 2 different groups for instrumentation with one non-augmented or one augmented SI screw contralaterally in a randomized fashion. The osteosynthesis followed a standard of 3D navigated percutaneous iliosacral screw positioning as described by Fuchs et al. A biomechanical setup for a qusi-static pull-out test of each SI screw was used. Construct stiffness and maximum pull-out force were calculated from the load-displacement curve of the machine data.
Results: :The mean value of the stiffness was 289.7 N/mm (SEM 97.1) for the non-augmented versus 501.6 N/mm (SEM 123.7) for the augmented group/semi-pelves. The mean pull-out force was 597.7 N (SEM 115.5) for the non-augmented versus 1336.8 N (SEM 221.1) for the augmented group/semi-pelves.
Conclusion: The stiffness of the augmented osteosynthetic specimens as well as the maximal pull-out force are significantly higher than that of the non-augmented ones.