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Enhancing pedicle screw fixation in the lumbar spine using allograft bone plug interference fixation
Bopha Chrea1, Harsha Malempati, Jeffrey R Campbell
1*Applied Biomechanics Laboratory, Department of Mechanical Engineering †Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA.
Journal of Spinal Disorders & Techniques
|April 9, 2013
Summary
Allograft bone plugs did not improve pedicle screw fixation in the spine, even in osteoporotic bone. This study investigated a biological alternative to cement augmentation for spinal implants.
Area of Science:
- Spinal surgery
- Orthopedic research
- Biomaterials science
Background:
- Osteoporotic spine fixation is challenging due to screw loosening and backout.
- Traditional cement augmentation carries risks like extravasation and embolization.
- There is a need for safer alternatives to enhance pedicle screw anchorage.
Purpose of the Study:
- To evaluate allograft bone plugs (ABPs) as a biological alternative to cement for pedicle screw fixation.
- To compare the axial pullout strength of augmented versus nonaugmented pedicle screws in human lumbar vertebrae.
Main Methods:
- A within-subjects controlled laboratory study using 24 human lumbar vertebrae.
- Two augmentation strategies with ABPs were tested against nonaugmented controls.
- Axial pullout tests were conducted using a servohydraulic system to measure fixation strength, displacement, and stiffness.
Main Results:
- Augmentation with 6-mm ABPs resulted in significantly weaker pullout strength compared to controls.
- No statistical difference in pullout strength was observed when using 5-mm ABPs.
- Fixation strength did not improve with ABP augmentation, even in osteoporotic bone specimens.
Conclusions:
- Cannulated allograft bone plugs did not enhance pedicle screw fixation in the spine.
- This biological augmentation strategy showed no benefit over traditional methods for improving screw anchorage.
- Further research is needed to develop effective augmentation techniques for spinal fixation.
