Bone Plate Screw Locking and Compression Mechanism
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Solution Overview
Problem
Current bone plate systems require multiple types of screws and components, leading to inventory management challenges and increased healthcare costs due to component waste, especially when treating smaller bones where reduced dimension and thickness profiles are necessary to minimize tissue irritation and hardware protrusion.
Innovation Solution
A bone plate system with tapered and threaded locking screw holes and non-threaded compression screw holes that can accommodate a single type of screw for both locking and axial loading, featuring a conically tapered external thread head and a bearing annulus to distribute axial loads effectively, reducing the risk of plastic deformation and allowing for high compression loads without additional washers or specialized instrumentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple types of screws and components are used for different fixation needs, then the system can provide specialized functions for locking and compression, but the component inventory increases and healthcare costs increase due to waste
Solution Approach 1:
The patent applies universality by designing a single bone screw that can function in both locking screw holes (with internal threads) and compression screw holes (without internal threads). The screw head includes a bearing annulus that distributes axial loads, allowing the same screw to provide both locking and compression functions. This eliminates the need for separate locking screws and compression screws, reducing component inventory while maintaining full fixation functionality.
2Object-affected harmful factors
If reduced dimension and thickness profile plates are used for smaller bones, then tissue irritation and hardware protrusion are minimized, but the plate-to-bone attachment becomes more challenging
Solution Approach 1:
The patent applies local quality by providing different hole configurations at different locations on the plate. The plate includes both locking screw holes (with internal threads for mechanical coupling) and compression screw holes (without internal threads for axial loading). This allows the surgeon to select the appropriate fixation type at each location based on local anatomical requirements, enabling reduced plate dimensions while maintaining secure attachment through optimized local fixation strategies.
3Length of stationary object
If smaller screws are used for reduced profile systems, then the plate thickness is reduced for smaller bones, but the screw strength decreases and they are prone to failure when torqued
Solution Approach 1:
The patent applies preliminary action by incorporating a bearing annulus at the head of the screw that is designed to contact the screw seat in compression holes. This bearing annulus distributes axial loads before they reach the screw threads, preventing stress concentration and potential failure. The preliminary load distribution mechanism allows smaller screws to be used without compromising strength, as the bearing annulus protects the screw from excessive torquing loads.
Data Source
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AI summary
An orthopedic screw system includes a screw with a locking head that can both lockingly engage in a fixed angle threaded screw hole to secure a plate to a bone without compression, and non-lockingly engage at a compression screw hole to provide compression between the plate and the bone. The structure of the system is particularly well adapted to plates and screws of small dimensions, such as screws smaller than 3.5 mm and is capable of providing high compressive force, on the order of 120 lbs of axial load, without significant plastic deformation between the screw and plate.