Undercut Fastener Threadforms for Multi-Axial Bone Fixation
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Solution Overview
Problem
Traditional fastener thread designs fail to provide sufficient fixation against multi-axial forces and off-axis loading scenarios, leading to potential loosening of surgical fasteners implanted in bone and other tissues.
Innovation Solution
Manufacturing undercut threadforms on fasteners involves a method using multiple cutting processes to create opposing undercut surfaces on helical threads, allowing for enhanced bone fixation and load sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional fastener thread designs are used, then manufacturing is simple, but fixation strength against multi-axial forces is insufficient
Solution Approach 1:
The cutting process is divided into multiple sequential cutting passes, with each pass creating a specific portion of the undercut threadform geometry. This segmentation allows complex undercut surfaces to be manufactured using standard cutting tools and processes, rather than requiring a single complex operation
Solution Approach 2:
The patent introduces oblique cutting trajectories that move the cutting tool along three-dimensional paths relative to the fastener axis. This dimensional approach enables creation of undercut surfaces with complex spatial geometry, achieving superior fixation strength while using conventional cutting equipment
2Manufacturing precision
If undercut threadforms are manufactured using conventional methods, then bone fixation is improved, but manufacturing precision is difficult to achieve
Solution Approach 1:
The manufacturing process is divided into multiple cutting passes, each responsible for creating specific undercut surfaces. This segmentation allows precise control over the geometry of each surface while using standard cutting tools, achieving high manufacturing precision without requiring complex single-step processes
Solution Approach 2:
The cutting process employs dynamic oblique trajectories that adjust the cutting tool's path in three-dimensional space. This dynamic approach enables precise formation of complex undercut geometries by controlling the relative motion between tool and workpiece, achieving high precision through motion control rather than complex tooling
Data Source
AI summary
Opposing undercut surfaces may be formed on a helical thread disposed about a shaft of a fastener by: rotating the shaft; translating a first cutting head medially toward the shaft along a first oblique trajectory of a first oblique cutting surface of the first cutting head; translating the first cutting head along a length of the shaft to form at least one of the opposing undercut surfaces on the helical thread; translating a second cutting head medially toward the shaft along a second oblique trajectory of a second oblique cutting surface of the second cutting head; and translating the second cutting head along a length of the shaft to form at least another one of the opposing undercut surfaces on the helical thread.