Variable-Angle Screw Threads for Pullout and Torque Resistance
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Solution Overview
Problem
Conventional medical and industrial screws suffer from inadequate multiaxial resistance, propensity for screw stripping, and loosening, leading to microfractures and post-surgical failure.
Innovation Solution
A screw with a unique angled and extended thread configuration, featuring uniformly spaced helical extensions with angled perpendicularly disposed posts and a sharp taper, providing increased pullout strength and torque resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional helical thread configurations are used, then screw implantation is facilitated, but multiaxial resistance and torque resistance are inadequate
Solution Approach 1:
The thread is segmented into distinct functional zones: a tapered distal end for initial implantation, a transition zone with varying angles, and a proximal parallel section for load bearing. This segmentation allows each zone to perform its specific function optimally while working together as an integrated system.
Solution Approach 2:
The thread design incorporates multi-axial loading capabilities by creating thread flanks that resist forces in multiple directions (axial, radial, and tangential). The angled thread configuration adds dimensional complexity that enables resistance to multiaxial stresses rather than just unidirectional axial loads.
2Ease of manufacture
If standard thread designs are used, then manufacturing is simple, but screw stripping and loosening occur
Solution Approach 1:
The thread parameters are optimized with specific angle ranges (30-45 degrees from horizontal), controlled thread depths (0.5-2.0mm), and defined pitch variations. These parameter changes create a thread form that distributes loads more evenly across the bone-screw interface, reducing stress concentrations that lead to stripping and loosening.
3Force
If traditional buttress thread designs are used, then axial loading resistance is provided, but multiaxial resistance capabilities are lacking
Solution Approach 1:
The thread design serves multiple functions simultaneously: the tapered distal end facilitates implantation while the angled threads provide axial load resistance, and the multi-axial thread flanks resist radial and tangential forces. This multi-functional design eliminates the need for separate thread forms for different loading conditions.
4Strength
If extended thread configuration is implemented, then pullout strength increases, but manufacturing complexity increases
Solution Approach 1:
The thread parameters are optimized with specific angle ranges (30-45 degrees from horizontal), controlled thread depths (0.5-2.0mm), and defined pitch variations. These parameter changes create a thread form that distributes loads more evenly across the bone-screw interface, reducing stress concentrations that lead to stripping and loosening.
Data Source
AI summary
Disclosed herein is a unique Variable Angle Loading Thread that can be utilized on a cannulated or non-cannulated screw, wire, or pin for a variety of end-uses, such as surgical purposes fastening fractured bones together and/or for attaching bone tissue to surrounding tissue. More particularly, this disclosure relates to an industrial and/or surgical medical thread form having a highly angled and extended thread configuration for increasing the pullout strength of the screw as well as torque resistance thereof. For surgical activities, as an example, such characteristics provide effective strength and torque resistance before bone stripping upon implantation. Whether provided with long or short thread (partial or full threading, in other words), such a unique angled and extended thread provides effective surgical fixation fastening fractured bones together and/or for attaching bone tissue to surrounding tissue and/or increasing healing capabilities.