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Updated: Dec 8, 2025
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An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
Published on: May 31, 2017
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Cortical threaded pedicle screw improves fatigue strength in decreased bone quality
Lukas Weiser1, Kay Sellenschloh2, Klaus Püschel3
1Department of Trauma Surgery, Orthopaedic Surgery and Plastic Surgery, University Medical Center Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany. Lukas.Weiser@med.uni-goettingen.de.
Summary
A modified cortical threaded pedicle screw significantly improves fatigue strength in vertebrae with poor bone quality. This enhanced screw design offers better spinal fusion outcomes in patients with compromised bone density.
Area of Science:
- Spine surgery
- Orthopedic biomechanics
- Biomaterials science
Background:
- Inadequate pedicle screw fixation in osteoporotic vertebrae is a significant clinical challenge.
- Poor bone quality compromises screw anchorage, leading to potential surgical failure.
- Novel screw designs are needed to enhance stability in compromised bone.
Purpose of the Study:
- To evaluate the impact of a modified cortical thread design on pedicle screw fatigue strength.
- To determine if this modification improves screw anchorage in vertebrae with reduced bone mineral density (BMD).
Main Methods:
- In vitro biomechanical testing of 14 human cadaveric lumbar vertebrae (L2-L3).
- Quantitative computed tomography (QCT) assessed bone mineral density (BMD).
- Comparison of standard double-threaded screws versus cortical (quad-threaded) screws under cyclic loading.
- Fatigue testing until 5.4 mm head displacement or 20° screw tilting.
Main Results:
- Cortical threaded screws demonstrated significantly higher mean fatigue load (324.7 N) compared to standard screws (264.9 N).
- This improvement was most pronounced in vertebrae with reduced BMD (cortical: 328.4 N vs. standard: 241.2 N).
- No significant difference was observed in vertebrae with normal BMD (cortical: 319.8 N vs. standard: 296.5 N).
Conclusions:
- Cortical threaded pedicle screws offer superior fatigue resistance compared to standard screws, particularly in vertebrae with diminished bone quality.
- This modified thread design represents a promising advancement for improving pedicle screw fixation in patients with osteoporosis or other conditions causing poor bone quality.
- Enhanced screw anchorage may lead to improved long-term outcomes in spinal fusion procedures.
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