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Quantification of Thread Engagement in Screw-Plate Interface of Polyaxial Locking System Using X-ray Computed
Tomasz Bartkowiak1, Daria Madalińska1, Patryk Mietliński1
1Institute of Mechanical Technology, Poznan University of Technology, 60-965 Poznań, Poland.
Materials (Basel, Switzerland)
|September 9, 2023
Summary
This study introduces a new method to measure thread engagement in orthopedic implants, crucial for bone fracture fixation. Accurate measurement, using X-ray micro-computed tomography, links engagement to fixation strength, guiding better screw placement.
Area of Science:
- Biomedical Engineering
- Orthopedic Surgery
- Materials Science
Background:
- Orthopedic implants for bone fracture fixation often require off-axis screw insertion due to anatomical constraints.
- Thread engagement is a critical factor influencing the mechanical strength and stability of screw-bone interfaces.
- Current methods for assessing thread engagement may not fully capture the complexities of off-axis screw placement.
Purpose of the Study:
- To develop and validate a novel method for quantifying thread engagement in mechanical connections, specifically for orthopedic plate implants.
- To investigate the impact of off-axis screw insertion and insertion torque on thread engagement.
- To establish the correlation between measured thread engagement and the push-out strength of the implant fixation.
Main Methods:
- Development of a quantification method utilizing X-ray micro-computed tomography (micro-CT) for non-destructive 3D imaging.
- Application of automated image processing techniques to analyze screw-plate interfaces and measure thread engagement.
- Performance of push-out tests on orthopedic plate implants to assess fixation strength under varying screw insertion conditions.
Main Results:
- The proposed method enables precise 3D measurement of thread engagement at the screw-plate interface.
- Thread engagement was found to decrease with increasing off-axis insertion angles and higher insertion torques.
- A strong correlation (R² > 0.6) was observed between average thread engagement and the push-out strength of the fixation.
Conclusions:
- The developed quantification method is effective for assessing thread engagement in biomedical implants.
- Off-axis screw insertion and high insertion torque negatively impact thread engagement and, consequently, fixation stability.
- Optimizing screw placement is essential for achieving robust and reliable fixation in orthopedic surgery.
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