Blunt-Tip Bone Screw With Cutting Flutes for Soft-Tissue Protection
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Solution Overview
Problem
Conventional bone screws for surgical rib or sternum fixation either cause significant damage to soft tissue when drilling through the back side of the bone due to their sharp tips or require pre-drilling, which can lead to soft-tissue wrap.
Innovation Solution
A bone screw design featuring a shaft with a helically threaded section and a tip that includes multiple lands with cutting flutes, allowing the screw to self-drill into the bone while minimizing damage to soft tissue by cutting a bore and forming a thread, with the tip angle and cutting edge configuration controlling the aggressiveness and bluntness of the cutting action.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a conventional self-tapping bone screw with a blunt tip is used, then soft tissue damage is minimized, but a drill is required to prepare the bore hole which causes soft-tissue wrap
Solution Approach 1:
The patent combines the self-drilling and self-tapping functions into a single bone screw design. The tip includes multiple cutting edges that can cut a bore hole without requiring a separate drill, while the blunt tip geometry minimizes soft tissue damage. The flutes in the tip channel bone chips away during the self-drilling process, preventing soft-tissue wrap.
Solution Approach 2:
The tip is segmented into multiple lands and cutting edges (typically 3-6 segments) arranged circumferentially. Each land has a cutting edge that contributes to bore cutting. This segmentation allows the tip to cut efficiently while maintaining a blunt overall profile that reduces soft tissue damage.
2Productivity
If a self-drilling bone screw with a sharp tip is used, then bone penetration is improved, but soft tissue damage occurs when the tip penetrates through the back side of the bone
Solution Approach 1:
The tip has locally sharp cutting edges on each land for effective bone cutting, while the overall tip profile remains blunt to minimize soft tissue damage. The cutting edges are sharp only where needed for cutting, while the outer envelope of the tip is rounded and blunt.
Solution Approach 2:
The tip has a curved or rounded outer profile rather than a sharp point, giving it a blunt appearance that reduces soft tissue damage. The cutting edges are formed on the surface of this curved tip, combining the blunt outer shape with sharp local cutting surfaces.
3Object-affected harmful factors
If a conventional self-tapping screw is used, then soft tissue damage is reduced, but the surgical process requires additional steps for pre-drilling
Solution Approach 1:
The bone screw performs multiple functions: it drills its own bore hole through the blunt tip with cutting edges, taps its own threads, and secures the fixation plate. This multi-functionality eliminates the need for separate drilling and tapping steps, simplifying the surgical procedure while maintaining soft tissue safety.
Solution Approach 2:
The bone screw is self-drilling and self-tapping. The tip cuts the bore hole without requiring a separate drill, and the helical threading on the shaft taps the threads as the screw is advanced into the bone. This self-service capability reduces the number of surgical steps and tools required.
Data Source
AI summary
In one embodiment, a bone screw includes a shaft having a proximal shaft end and a distal shaft end spaced from the proximal shaft end in a distal direction along a central axis. The shaft is helically threaded between the proximal and distal shaft ends. A tip extends from the distal shaft end in the distal direction, and defines a plurality of lands with cutting flutes disposed between adjacent lands. Each land has a bore-cutting edge that extends from an inner cutting edge end to an outer cutting edge end. The inner cutting edge end is disposed at a center of the distal end of the tip, and the outer cutting edge end is spaced from the center of the distal end of the tip. The bore-cutting edges may blunt the feel of the tip so as to reduce the likelihood of soft-tissue damage.