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Updated: Jul 16, 2026
09:07
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
Effect of screw torque level on cortical bone pullout strength.
Tammy M Cleek1, Karen J Reynolds, Trevor C Hearn
1School of Informatics and Engineering, Flinders University, Adelaide, SA, Australia. tammy.cleek@flinders.edu.au
Journal of Orthopaedic Trauma
|February 17, 2007
Summary
Overtightening cortical screws past 86% of maximum torque (Tmax) in ovine tibiae significantly reduces bone holding strength. Clinical tightening levels compromise screw purchase, indicating potential damage to bone fixation.
Area of Science:
- Orthopedic biomechanics
- Surgical implant technology
Background:
- Cortical screw fixation is crucial for fracture healing.
- Optimizing screw tightening torque is essential for implant stability and bone integrity.
Purpose of the Study:
- To analyze cortical screw tightening stiffness during automated insertion.
- To evaluate the impact of three torque levels on bone holding strength via screw pullout tests.
Main Methods:
- Ovine tibiae were used, with screws inserted at 50%, 70%, and 90% of predicted maximum torque (Tmax).
- Screw pullout tests assessed holding strength, with force values normalized by cortical thickness.
Main Results:
- Tightening to 86% Tmax, a clinical level, occurred post-bone yield, causing a 51% loss in stiffness.
- Screw holding strength was highest at 70% Tmax (2707 N) and significantly lower at 90% Tmax (2344 N).
Conclusions:
- Clinical screw tightening levels (86% Tmax) exceed bone's yield point, potentially damaging fixation.
- High torque levels compromise screw holding strength, necessitating further research for optimal torque parameters.
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