Dual-Helical Bone Fastener Threads for Off-Axis Load Fixation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional fastener thread designs fail to provide sufficient fixation and load sharing under multi-axial and off-axis loading conditions in surgical procedures, leading to loosening of fasteners implanted in bone and other tissues.
Innovation Solution
The development of fasteners with dual helical threads featuring concave and convex undercut surfaces, designed using a specific milling process that creates asymmetrical threads to enhance bone fixation and load distribution, including a 'dual start' or 'dual lead' thread configuration and varying thread dimensions to accommodate different loading patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fastener thread designs are used, then manufacturing is simple, but bone fixation and load sharing under multi-axial and off-axis loading conditions are insufficient
Solution Approach 1:
The patent applies asymmetry by designing threads with non-uniform pitch and depth variations along the fastener length, creating asymmetrical thread profiles that optimize load distribution under multi-axial and off-axis loading conditions. The thread geometry transitions from uniform to variable pitch and depth to improve bone fixation reliability
Solution Approach 2:
The patent implements local quality by varying thread properties (pitch, depth, profile) at different locations along the fastener length. The threads have different characteristics in proximal versus distal regions to accommodate varying loading conditions and bone density, optimizing fixation at each location rather than using a uniform design throughout
2Strength
If uniform thread pitch and depth are used, then manufacturing is easier, but load distribution under multi-axial forces is inadequate
Solution Approach 1:
The patent applies parameter changes by systematically varying thread pitch and depth along the fastener length. The thread pitch transitions from coarser to finer intervals, and depth varies to create optimal load distribution patterns. These parameter variations improve load sharing capability while requiring advanced manufacturing methods
3Stability of the object's composition
If simple thread geometry is used, then manufacturing precision requirements are lower, but fixation stability under off-axis loading is insufficient
Solution Approach 1:
The patent employs asymmetry in thread geometry design, creating non-uniform thread profiles with varying pitch and depth that provide enhanced stability under off-axis loading. The asymmetrical design requires precise manufacturing to achieve the intended mechanical performance and fixation stability
Data Source
AI summary
A process of forming a fastener with improved threading to resist multi-axial forces and off-axis loading scenarios is provided. The process may include placing first and second mill tools adjacent a shaft of the fastener having a proximal end and a distal end, rotating the shaft and the first and second mill tools, and translating the first and second mill tools along at least part of a length of the shaft to form: a first concave undercut surface oriented toward the proximal end, a first convex undercut surface oriented toward the distal end, a second concave undercut surface oriented toward the distal end, and a second convex undercut surface oriented toward the proximal end.