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Related Concept Videos

Self-Locking Screw01:16

Self-Locking Screw

A square-threaded screw jack is a mechanical device widely used for lifting heavy loads or applying considerable force. One of the key features that can make a screw jack more effective and reliable is its self-locking capability.
A square-threaded screw jack carrying a load is considered self-locking if the screw retains its position even after the moment applied to it is removed.
Frictional Forces on Screws01:17

Frictional Forces on Screws

Screws are characterized by a helical ridge known as a thread wrapped around a cylindrical shaft. They are commonly used as fasteners to hold objects together or to transmit power and motion in machines. One type of screw that is particularly useful for transmitting power is the square-threaded screw.
A jack with a square-threaded screw is a mechanical device used to lift heavy loads by applying a force at its handle. When the force is applied, the screw turns, raising the load. The screw can...
Screw: Problem Solving01:21

Screw: Problem Solving

In mechanical engineering, the interaction between a threaded screw shaft and a plate gear involves analyzing the resisting torque on the plate gear that can be overpowered when a specific torsional moment is applied to the shaft. To better comprehend this concept, consider a generic situation with a threaded screw shaft with a given mean radius and lead and a plate gear with a specified mean radius. The coefficient of static friction between the screw and gear is also provided.
To evaluate the...
General Case of Eccentric Axial Loading01:12

General Case of Eccentric Axial Loading

Unsymmetrical bending occurs when the bending moment applied to a structural member does not align with its principal axis. This misalignment leads to complex stress distributions and deflection patterns that differ from symmetrical bending, which are essential for designing structures to withstand different loading conditions.
Consider a member subjected to equal and opposite forces that are applied along a line that does not coincide with the member's neutral axis. In unsymmetrical bending,...
Machines: Problem Solving I01:22

Machines: Problem Solving I

A toggle clamp is a mechanical device commonly used for holding and clamping objects in various applications, such as woodworking, metalworking, and assembly operations. Consider a toggle clamp subjected to a force of 200 N at the handle. The vertical clamping force can be calculated, provided the dimensions of the toggle clamp are known.
The toggle clamp system is a machine structure consisting of movable, pin-connected multi-force members that form a stabilized system to transmit forces. The...
Eccentric Axial Loading in a Plane of Symmetry01:16

Eccentric Axial Loading in a Plane of Symmetry

Eccentric axial loading occurs when an axial load is applied away from the centroidal axis of a structural member. This scenario is common in engineering, where structural elements may not be directly aligned due to various design or functional requirements.

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Related Experiment Video

Updated: May 9, 2026

A Minimally Invasive Model to Analyze Endochondral Fracture Healing in Mice Under Standardized Biomechanical Conditions
06:41

A Minimally Invasive Model to Analyze Endochondral Fracture Healing in Mice Under Standardized Biomechanical Conditions

Published on: March 22, 2018

A biomechanical study comparing polyaxial locking screw mechanisms.

Jonah Hebert-Davies1, G-Yves Laflamme, Dominique Rouleau

  • 1University of Montréal, Hôpital du Sacré Cœur, 5400 Gouin Ouest, Local J-3245, Montréal, Québec, Canada H4J 1C5. jonah.davies@gmail.com

Injury
|July 16, 2013
PubMed
Summary

Polyaxial locking plates offer surgical flexibility but reduce screw resistance. Even with polyaxial designs, non-perpendicular screw insertion angles decrease load to failure, suggesting a narrower safe insertion zone than manufacturer recommendations.

Keywords:
AngulationFracturesLoad to failureLocking plateMechanical testingPolyaxial screws

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An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
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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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Last Updated: May 9, 2026

A Minimally Invasive Model to Analyze Endochondral Fracture Healing in Mice Under Standardized Biomechanical Conditions
06:41

A Minimally Invasive Model to Analyze Endochondral Fracture Healing in Mice Under Standardized Biomechanical Conditions

Published on: March 22, 2018

An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
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

Area of Science:

  • Orthopedic Surgery
  • Biomedical Engineering
  • Materials Science

Background:

  • Locking plates are standard in fracture repair.
  • Polyaxial locking plates offer improved screw placement flexibility.
  • Uniaxial screws show reduced strength when inserted off-axis.

Purpose of the Study:

  • To evaluate the biomechanical resistance of polyaxial locking plates with non-perpendicular screw insertion.
  • To test the hypothesis that polyaxial plates also experience reduced strength with angled screws.

Main Methods:

  • Tested four small fragment plate types (1 monoaxial, 3 polyaxial).
  • Developed a biomechanical model to assess screw failure (defined as >50% force loss).
  • Inserted screws at 0°, 10°, and 15° angles.

Main Results:

  • Monoaxial screws showed a 60% force reduction at 10°.
  • Two polyaxial systems had significant force reductions (45%, 34%) at 15°.
  • Polyaxial screws exhibited limited reduction at 10°, but results varied by locking mechanism.

Conclusions:

  • Polyaxial plates provide surgical options but decrease load-bearing capacity.
  • The safe screw insertion zone may be closer to 20°, not 30° as suggested.
  • Different polyaxial locking mechanisms impact screw resistance differently.