Arthroplasty Implant Thread Undercuts for Multi-Axial Load Sharing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Joint arthroplasty devices face issues with loosening due to multi-axial forces and off-axis loading scenarios, as traditional thread designs fail to provide sufficient fixation and load sharing at the bone/implant interface.
Innovation Solution
The development of arthroplasty implants with improved thread designs, including dual helical threads with angled concave undercut surfaces and varying diameters, along with flange components and attachment features, to enhance bone fixation and load sharing under multi-axial and off-loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional thread designs are used in arthroplasty implants, then the implant structure is simple and easy to manufacture, but the fixation strength and load sharing capability are insufficient under multi-axial forces
Solution Approach 1:
The patent applies local quality by varying thread parameters (depth, pitch, diameter, undercut geometry) along different segments of the implant shaft. The proximal and distal portions have different thread characteristics optimized for their specific loading conditions, with the proximal portion having deeper threads for cortical bone engagement and the distal portion having shallower threads for cancellous bone engagement.
Solution Approach 2:
The thread design is segmented into multiple distinct regions along the shaft length, each with unique geometric parameters. This includes different thread depths, pitches, and undercut configurations in proximal versus distal portions, allowing each segment to address specific mechanical requirements of different bone types and loading zones.
2Reliability
If traditional thread designs are used in arthroplasty implants, then the manufacturing process is simple, but the implant reliability under off-axis loading is insufficient
Solution Approach 1:
The patent employs parameter changes by systematically varying thread geometry parameters including depth, pitch, diameter, and undercut angle along the shaft length. These parameter variations are designed to optimize performance under multi-axial and off-axis loading conditions while maintaining manufacturability through standardized fabrication processes.
3Strength
If uniform thread diameter is used along the shaft, then the manufacturing is easier, but the load distribution and fixation effectiveness are reduced under multi-axial forces
Solution Approach 1:
The patent implements local quality through diameter variations in different shaft portions. The proximal shaft portion has a larger diameter with deeper threads for cortical bone engagement, while the distal shaft portion has a smaller diameter with shallower threads for cancellous bone engagement, optimizing load distribution across different bone types.
Data Source
AI summary
A bone implant may include a shaft having a proximal end, a distal end, a longitudinal axis, a proximal shaft portion, and a distal shaft portion. The proximal shaft portion may include a first minor diameter, and a first helical thread disposed about the proximal shaft portion defining a first major diameter. The first helical thread may include a first concave undercut surface. The distal shaft portion may include a second minor diameter, and a second helical thread disposed about the distal shaft portion defining a second major diameter. The second helical thread may include a second concave undercut surface. The first and second concave undercut surfaces may be angled towards the distal end of the shaft. The second minor diameter may be smaller than the first minor diameter and the second major diameter may be smaller than the first major diameter.