Passive Screw Locking Mechanism for Bone Plate Fixation
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Solution Overview
Problem
Current bone fixation devices face issues with unintentional screw loosening, which can lead to reduced effectiveness and complications such as erosion and irritation, often requiring additional locking mechanisms that complicate procedures and limit screw insertion trajectories.
Innovation Solution
A passive locking mechanism using an annular feature in a thru-hole of a bone plate or bushing that engages a bone screw, allowing for polyaxial rotation and secure retention without additional locking steps, preventing screw back-out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional locking mechanisms are applied to prevent screw back-out, then screw retention reliability is improved, but device complexity and procedure complexity increase
Solution Approach 1:
The patent combines the locking function with the existing bone plate structure by integrating a cam mechanism directly into the plate body. The cam feature is formed as part of the bone plate, eliminating the need for separate locking components. When the bone screw is inserted, the cam mechanism automatically engages to prevent back-out, merging the locking function into the existing structure rather than adding separate elements.
Solution Approach 2:
The cam mechanism is designed to automatically engage and lock the bone screw in place without requiring additional tools or manual locking steps. The geometry of the cam feature and the screw interaction creates a self-locking system where the insertion motion itself activates the locking mechanism, making the system self-servicing and eliminating the need for separate locking operations.
2Reliability
If precise alignment of bone screw with thru-hole is required, then screw locking reliability is improved, but insertion trajectory flexibility is reduced
Solution Approach 1:
The cam mechanism incorporates a polyaxial rotation capability that allows the bone screw to rotate freely around the cam feature during insertion. This dynamic rotation feature enables the screw to be inserted at various angles and trajectories while still achieving reliable locking. The cam's geometry maintains engagement regardless of the insertion path, providing adaptability while preserving locking reliability.
Data Source
AI summary
Methods and devices are provided for passively locking a bone screw within a bone plate. In particular, the methods and devices allow a bone screw to be locked within a thru-hole in a bone plate without requiring any additional locking steps. In an exemplary embodiment, an annular feature is provided in a thru-hole of a bone plate, or in a bushing that is disposed within a thru-hole of a bone plate, for engaging a bone screw. The annular feature can be configured such that it allows the bone screw to be inserted through the thru-hole at various insertion angles while still being effective to prevent back-out of the bone screw, thereby locking the screw to the plate.