Lateral Spine Plate Anti-Rotation Setscrew Locking Mechanism
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Solution Overview
Problem
Existing lateral spine plate implants are deficient in preventing rotation of bone screws after attachment, which compromises the integrity and functionality of the implant in preventing horizontal movement of vertebral bodies.
Innovation Solution
A lateral spine plate design featuring configured setscrews, bone screw bores, and bone screws with anti-rotation features such as serrations, knurling, or helical cutouts, which allow up to 360° angulation and fixation, preventing bone screw rotation by engaging with the setscrew pocket to secure the bone screw head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lateral spine plates are used without anti-rotation features, then the device complexity is low, but bone screw rotation occurs after attachment compromising spine plate integrity
Solution Approach 1:
The bone screw is divided into functional segments: the head with external anti-rotation features (serrations, knurling, or helical cutouts) and the threaded shank. The plate bore is segmented with an inner anti-rotation surface and outer threading. This segmentation allows each component to perform its specific function while maintaining overall system reliability.
Solution Approach 2:
Anti-rotation features are applied asymmetrically at specific locations on the bone screw head and plate bore. The serrations, knurling, or helical cutouts create an asymmetric engagement pattern that prevents rotation in one direction while allowing controlled insertion, thereby preventing bone screw rotation without requiring complete structural asymmetry throughout the entire device.
Solution Approach 3:
The anti-rotation features utilize curved and rounded geometries including spherical or domed engagement surfaces, helical cutouts that wrap around the screw head, and knurling patterns. These curved features provide smoother engagement and more reliable anti-rotation performance compared to sharp angular features, while distributing stresses more evenly.
2Reliability
If anti-rotation features are added to prevent bone screw rotation, then spine plate integrity is improved, but the manufacturing complexity increases
Solution Approach 1:
The anti-rotation features are implemented by modifying geometric parameters of existing components rather than adding separate parts. Serrations, knurling, and helical cutouts are created through controlled deformation or removal of material during standard manufacturing processes, changing local surface parameters without fundamentally altering the manufacturing workflow or requiring additional assembly steps.
3Manufacturing precision
If configured setscrews with anti-rotation features are used, then bone screw orientation fixation is improved, but the device complexity increases
Solution Approach 1:
Multiple functions are merged into the setscrew component: it provides compression loading through threading engagement with the bone screw, orientation fixation through engagement with anti-rotation features on the screw head, and structural support as part of the plate assembly. This consolidation eliminates the need for separate compression devices and orientation control mechanisms, reducing overall device complexity despite the enhanced functionality of the setscrew itself.
Data Source
AI summary
A lateral spine implant has a plate, configured bone screws, and configured setscrews providing locking of bone screw movement. The plate has at least two identically configured bone screw bores, each one with a spherical seat at a bottom opening, and threads around the inner circumference of a top opening. Each setscrew has a cylindrical body with external threads that mate with inner threads of the bone screw bore in order to affix the setscrew to the plate. A threaded spherical pocket is provided in a bottom of the setscrew body which conjoins with the spherical bone screw head to secure the setscrew with the bone screw head, fixing bone screw orientation/angulation. The bone screw head has a formation or formations about at least a portion of its exterior circumference that cooperate with the threads of the spherical pocket of the plate in order to fix bone screw orientation/angulation.