Orthopedic Screw Thread Ribbon Resilient Flange
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Solution Overview
Problem
Existing orthopedic screws face issues with decreased 'pull out strength' due to thread deformation and bone ingrowth, making revision procedures difficult in subsequent surgeries.
Innovation Solution
The orthopedic screw features a shaft with a thread ribbon that includes a rigid base and a resilient flange portion, which expands when subjected to a pull-out force, increasing the outer thread diameter and enhancing pull-out strength while maintaining the ability for surgical revision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If an expanding thread section is used to increase pull out strength, then the pull out strength is improved, but the screw becomes difficult to revise in subsequent surgeries due to bone ingrowth and collapse prevention
Solution Approach 1:
The thread transitions from a static solid cross-section to a dynamic hollow configuration that can expand and collapse. The hollow thread allows the screw to expand radially for increased pull-out strength while maintaining the ability to collapse for easy removal during revision surgeries, resolving the contradiction between strength and revisability.
Solution Approach 2:
The thread geometry changes from solid to hollow, fundamentally altering the structural parameters. This parameter change enables the thread to achieve higher radial expansion capability for improved pull-out strength while the hollow configuration prevents bone ingrowth, maintaining revisability.
2Strength
If material is filled in the thread cross-section to prevent fracture, then thread strength is improved, but the thread outer diameter decreases due to rounding of the crest
Solution Approach 1:
The solid thread material is segmented into a hollow configuration with internal void space. This segmentation removes the material that would round the crest and reduce outer diameter, while the remaining structural walls provide sufficient strength and the hollow space allows for radial expansion to increase pull-out strength.
Solution Approach 2:
The thread walls function as flexible shells that can expand radially outward to increase the effective outer diameter for enhanced pull-out strength. The thin-walled hollow structure avoids the crest rounding issue of solid threads while providing the necessary structural integrity through the shell configuration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design significantly increases the pull-out strength and facilitates easy removal and revision of the screw site, preventing bone ingrowth and thread failure, thus ensuring effective fixation and subsequent surgical access.
Implementation Method 1
The flange portion is resilient and extends away from the shaft at a second angle greater than the preset angle to form a second outer thread diameter greater than the preset outer thread diameter when the orthopedic screw is subjected to a pull out force
Data Source
AI summary
An orthopedic screw having a shaft and a thread ribbon is provided. The shaft includes a proximal driving end and a distal end. The thread ribbon extends around the shaft and including a base portion that is rigidly attached to the shaft and a flange portion that is resilient. The flange portion extends away from the shaft at a preset angle to form a preset outer thread diameter in a preset configuration. The flange portion extends away from the shaft at a second angle greater than the preset angle to form a second outer thread diameter greater than the preset outer thread diameter when the orthopedic screw is subjected to a pull out force.