Convex Set Screw Design for Spinal Rod Alignment
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Solution Overview
Problem
Existing orthopedic tools face challenges in aligning spinal rods with pedicle screws due to misalignment, leading to issues such as lateral torque, cold welding, and mechanical stress on vertebrae during spinal fusion surgery.
Innovation Solution
A set screw design with a convex surface and traversing opening, along with a set screw driver, ensures proper alignment and minimizes sharp edges, reducing lateral forces and preventing cold welding by providing a larger contact surface and controlled engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional set screw with flat surface is used to attach spinal rod to pedicle screw, then the attachment function is achieved, but misalignment occurs causing lateral torque and mechanical stress on vertebrae
Solution Approach 1:
The set screw features a convex spherical surface instead of a flat surface, allowing the screw to self-align with the spinal rod through curved surface contact. This spherical geometry enables the set screw to accommodate minor misalignments and achieve proper positioning without creating lateral torque on the vertebrae, while maintaining secure attachment.
2Reliability
If conventional set screw design is used, then attachment is achieved, but sharp edges cause cold welding and mechanical stress
Solution Approach 1:
The convex spherical surface of the set screw eliminates sharp edges by providing continuously curved surfaces that contact the spinal rod. This curved geometry prevents stress concentration and eliminates the cold welding effect that occurs with sharp-edged components, while maintaining secure attachment through increased contact surface area.
3Ease of operation
If conventional set screw with limited contact surface is used, then attachment function is achieved, but alignment precision is insufficient
Solution Approach 1:
The convex spherical surface provides a larger effective contact area with the spinal rod compared to conventional flat-set screw designs. This curved surface geometry enhances alignment capability by allowing the set screw to self-position and accommodate variations in rod placement, achieving precise alignment without requiring extremely tight manufacturing tolerances.
Data Source
Figure 1A~1B
Figure 1C
Figure 2A
AI summary
A set screw for threadable engagement with a head of a pedicle screw for holding a spinal rod, the set screw having a spinal rod facing side and a set screw driver facing side, the set screw including an opening at the set screw driver facing side for engaging with the set screw driver, and a convex surface at the rod facing side, an apex of the convex surface substantially corresponding with a rotational central axis of the set screw.