Angled Cutting Flutes in Cannulated Bone Screws
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Cannulated bone screws with existing cutting flutes struggle to efficiently penetrate bone material due to the cannulation, which can hinder their ability to advance effectively and cause damage to adjacent bone.
Innovation Solution
The design incorporates aggressive cutting features with cutting flutes and teeth that extend to the distal end of the bone screw, providing a strong initial bite and a slicing action to minimize damage and facilitate insertion, allowing for self-drilling functionality and reduced insertion torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If cannulation is added to allow guidewire passage, then guidance capability is improved, but penetration ability through bone material deteriorates
Solution Approach 1:
The distal end of the bone screw is segmented into multiple cutting flutes (typically 3-6) that extend along a portion of the shaft. These flutes create discrete cutting edges that rotate during insertion, enabling effective bone penetration despite the hollow cannulated structure. The segmentation allows the screw to maintain structural integrity while providing aggressive cutting action.
Solution Approach 2:
The cutting flutes are concentrated at the distal end and extend only along a portion of the shaft length, creating localized cutting functionality where it is most needed for initial penetration. The cannulated portion can extend further proximally without cutting features, optimizing both guidance capability and penetration ability in different regions of the same device.
2Ease of operation
If cutting flutes are added to facilitate insertion, then penetration ability is improved, but damage to adjacent bone increases
Solution Approach 1:
The cutting flutes are designed to rotate during insertion, creating a dynamic cutting action that slices through bone material rather than statically scraping or grinding. This rotational cutting mechanism reduces friction and heat generation, minimizing thermal necrosis and mechanical damage to adjacent bone tissue while maintaining effective penetration.
Solution Approach 2:
The cannulated structure, which initially appears to weaken the screw and reduce penetration ability, is converted into a benefit by adding cutting flutes that create controlled chip formation. The flutes capture and evacuate bone chips through the cannulated channel, preventing chip clogging and reducing the need for excessive insertion force that would damage adjacent bone.
3Productivity
If cutting flutes extend to distal end for self-drilling, then insertion efficiency is improved, but number of rotations required increases
Solution Approach 1:
The cutting flutes are pre-configured with optimized geometry (depth, width, angle) that enables aggressive bone engagement from the moment of insertion. The flutes create initial purchase and chip formation patterns that reduce resistance during subsequent rotations, allowing the screw to advance with fewer total rotations compared to designs with less aggressive preliminary cutting features.
Solution Approach 2:
The cutting flutes are designed with specific geometric parameters including optimized depth (typically 0.5-2.0mm), width, and helical angle (15-45 degrees) that balance cutting aggressiveness with rotational efficiency. These parameter optimizations enable effective bone penetration while minimizing the number of rotations required, achieving both high productivity and time efficiency.
Data Source
Figure 1~2
Figure 3~5
Figure 6A
AI summary
A bone screw, comprising a proximal end and a distal end spaced from the proximal end in a distal direction along a longitudinal axis of the bone screw and a cannulation extending from the proximal end to the distal end. The bone screw further including a threaded region extending along at least a portion of a length of the screw, the length extending from the proximal end to the distal end. The threaded region defining at least one external thread that extends about the longitudinal axis along a helical path. The threaded region includes at least one flute that extends to the distal end of the bone screw. The at least one flute defines an associated at least one cutting tooth that, in turn, defines a cutting face oriented so as to define an angle with respect to the longitudinal axis. The angle is in the range of about 5 degrees and about 25 degrees, and the flute circumferentially interrupts at least a portion of the external thread.