Shape Memory Orthopedic Staple with Variable Thickness Legs
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Solution Overview
Problem
Existing orthopaedic staples fail to provide even compressive force distribution along the length of the staple legs, leading to undesirable compression patterns that can allow bone fragments to separate under tensile forces.
Innovation Solution
The use of shape memory material for staple legs that transition from a constrained parallel position to a relaxed converging position, with increasing thickness from the tip to the protruding portion, providing a more even compressive force and resistance to backout through grasping portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If springs are used to drive bone compression in existing staples, then compressive force is provided to bone fragments, but the compression force is focused only at the bent portion where staple legs meet the springs, creating an uneven compression pattern
Solution Approach 1:
The staple legs are designed with varying thickness along their length, with the thickest portion located at the distal end. This non-uniform thickness distribution creates different local stiffness characteristics, allowing the staple to provide compressive force along the entire length of the staple legs rather than concentrating it at a single point, thereby achieving even compression throughout the bone fragment contact area.
2Force
If compression force is focused at the tips of existing staples, then insertion is facilitated, but tensile forces distanced from the compression center point can pull fragments apart
Solution Approach 1:
The staple legs are pre-formed with a curved configuration and varying thickness before implantation. The thickest portion is positioned at the distal end to preemptively establish the compression center along the entire length of the staple leg. This preliminary geometric configuration ensures that when the staple is inserted and deployed, the compressive force is automatically distributed evenly along the full length, creating inherent resistance to tensile separation forces throughout the bone fragment interface.
3Ease of manufacture
If staple legs are made with uniform thickness, then manufacturing is simplified, but compressive force cannot be delivered evenly along the length of the staple leg
Solution Approach 1:
The staple legs incorporate a deliberate thickness gradient along their length, with the maximum thickness located at the distal end and progressively thinner toward the proximal end. This non-uniform geometry is achieved through manufacturing processes such as selective material deposition or precision machining, creating localized variations in mechanical properties that enable even compressive force distribution while maintaining overall structural integrity and biocompatibility.
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
This design ensures a more uniform compressive force distribution along the staple legs, enhancing bone fragment compression and preventing backout by utilizing the shape memory material's ability to revert to its original shape, thus improving bone healing and stability.
Implementation Method 1
one or more staple legs formed from a shape memory material that can provide a more even compressive force distribution across the length of the one or more staple legs than known devices
Data Source
AI summary
An orthopedic staple includes a bridge portion having a pair of ends and a staple leg formed from a shape memory material connected to each of the pair of ends. The staple legs have a constrained position where the staple legs are generally parallel to one another and a relaxed position where the staple legs generally converge toward one another. Each of the staple legs has a protruding portion with a maximum leg thickness and a tip, with each of the staple legs increasing in thickness from the tip to the protruding portion. The bridge portion and each of the protruding portions define grasping portions therebetween that are configured to provide resistance to backout of the orthopedic staple.