Bone Fixation Threads and Guide Blocks for Off-Axis Stability
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Solution Overview
Problem
Traditional bone fixation fasteners fail to provide sufficient fixation under multi-axial forces and off-axis loading scenarios, leading to loosening over time.
Innovation Solution
Bone fixation devices with improved thread and compression designs, including dual-start helical threads and guide blocks, to enhance fixation and load sharing at the bone/fastener interface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional bone fastener thread designs are used, then the device complexity is low, but the fixation strength and reliability under multi-axial forces are insufficient
Solution Approach 1:
The thread design is segmented into multiple functional zones: a first portion with a first pitch for initial engagement and compression, and a second portion with a second pitch for enhanced load distribution. This segmentation allows each zone to perform its specific function optimally, resolving the contradiction between simplicity and effectiveness.
Solution Approach 2:
Different regions of the thread are given different local properties: the first portion has coarser threading for compression, while the second portion has finer threading for load distribution. This local differentiation enables the single fastener to handle multiple loading conditions effectively.
2Reliability
If traditional single-start threads are used, then the manufacturing is simple, but the load sharing capability under off-axis loading is insufficient
Solution Approach 1:
The thread is divided into two distinct portions with different pitch characteristics, allowing the fastener to distribute loads more effectively under off-axis conditions while maintaining manufacturability through standard threading processes.
Solution Approach 2:
The pitch parameter is varied along the length of the thread, transitioning from a first pitch in the initial portion to a second pitch in the second portion. This parameter change enables improved load sharing without requiring complex manufacturing techniques.
3Stability of the object's composition
If uniform thread pitch is used throughout the fastener, then the manufacturing precision is easier to maintain, but the fixation stability under multi-axial forces deteriorates
Solution Approach 1:
The thread is segmented into portions with different pitch values, with the transition point positioned to optimize fixation stability. This segmentation allows the fastener to maintain stability under multi-axial forces while using standard manufacturing tolerances for each segment.
Solution Approach 2:
The first portion of the thread with its specific pitch is designed to perform preliminary compression and seating of the fastener, preparing the bone interface for the second portion to provide enhanced stability under multi-axial loading.
Data Source
AI summary
A bone disunion instrument system may include a first bone pin, a second bone pin, and a guide block. The guide block may include first and second bone pin holes to receive the first and second bone pins, and a window intermediate the first and second bone pin holes. The first bone pin may be anchored in a first bone portion and inserted through the first bone pin hole, and the second bone pin may be anchored in a second bone portion and inserted through the second bone pin hole to impart a compression or distraction force on a bone disunion between the first and second bone portions. The window formed through the guide block may provide access for an implant placed through the window to stabilize the bone disunion while the bone disunion is placed under a compression or distraction force.