Orthopedic Screw Asymmetric Thread Profile for Bone Stability
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Solution Overview
Problem
Orthopedic screws used in bone fracture stabilization often deviate from their proper position or migrate, leading to instability and potential collapse of bone structures like the femoral head and neck, due to inadequate fixation and stress distribution.
Innovation Solution
An orthopedic screw design featuring a helical thread with specific tooth geometry and orientation, including leading and trailing flanks, crests, and chamfered edges, which minimizes bone removal and provides enhanced fixation by dispersing load evenly across the bone surface, preventing migration and collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional orthopedic screw design is used, then the screw can be implanted into bone, but the screw may deviate from its proper position, retract laterally, or migrate medially through the bone
Solution Approach 1:
The thread profile is designed with non-uniform geometry where the leading flank has a first angle and the trailing flank has a second angle relative to the longitudinal axis. This local variation in thread quality creates asymmetric engagement with the bone, providing directional stability and preventing lateral retraction while maintaining secure fixation.
Solution Approach 2:
The thread profile employs asymmetric geometry with the leading flank angle differing from the trailing flank angle. This asymmetry creates a mechanical stop against lateral movement and prevents the screw from migrating medially through the bone, thereby improving position stability and preventing bone collapse.
2Strength
If the screw thread engages deeply with the bone, then fixation strength is improved, but bone removal increases and structural integrity is compromised
Solution Approach 1:
The thread profile parameters are optimized with specific angular relationships between the leading and trailing flanks. This parameter optimization allows the thread to engage bone effectively for strong fixation while minimizing the volume of bone removed during insertion, preserving structural integrity.
3Ease of manufacture
If the thread profile is simplified for easier manufacturing, then production cost decreases, but load distribution capability is reduced
Solution Approach 1:
The thread profile incorporates localized geometric variations with specific leading and trailing flank angles that optimize load distribution. This local quality enhancement is integrated into a manufacturable helical thread structure, achieving both ease of production and superior mechanical performance.
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 screw effectively stabilizes bone fractures by reducing the likelihood of lateral retraction or medial migration, maintaining contact with the bone and distributing load efficiently, thereby reducing the risk of bone collapse and ensuring long-term stability.
Implementation Method 1
The thread extends helically from the shaft to define a plurality of teeth, each of the plurality of teeth being separated by a root
Implementation Method 2
at least a portion of the crests of the plurality of teeth extend in a second direction essentially perpendicular to the first direction of the load
Data Source
AI summary
An orthopedic screw that may be used to align and stabilize a bone fracture and a method for using the same.