Bone Plate System With Oxygen Diffusion Hardened Screw Head
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Solution Overview
Problem
Conventional bone plate systems face challenges such as high manufacturing complexity, limited angle stability, and usability issues due to complex locking mechanisms, which increase costs and complicate the insertion and removal of screws, while also requiring strong and biocompatible materials for effective bone healing.
Innovation Solution
A bone plate system with a simple hole design featuring tapering portions allowing variable-angle screw insertion, a self-tapping screw with a harder outer surface for efficient locking and reduced manufacturing costs, and a method for oxygen diffusion hardening to enhance surface hardness and corrosion resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional locking mechanisms with discrete columns of teeth or thread segments are used in plate holes, then screw locking capability is achieved, but device complexity and manufacturing costs increase
Solution Approach 1:
The invention extracts the locking function from the plate hole structure and relocates it to the screw head. The plate hole becomes a simple cylindrical or conical receptacle without any internal locking features, while the screw head incorporates all locking mechanisms including variable angle engagement surfaces and locking elements. This extraction simplifies the plate manufacturing while maintaining reliable screw locking capability.
Solution Approach 2:
The invention introduces an intermediary locking element within the screw head that mediates between the simple plate hole and the bone. This locking element can engage with the bone at variable angles while providing stable coaxial locking within the plate hole, effectively decoupling the plate hole simplicity from the locking functionality.
2Adaptability or versatility
If variable-angle locking mechanisms are implemented, then adaptability for different insertion angles is improved, but device complexity and voluminous design increase
Solution Approach 1:
The invention implements dynamic adaptability by designing the screw head with a conical engagement surface that can naturally accommodate insertion at various angles. The locking element within the screw head can dynamically adjust its position and orientation to engage the bone at the required angle while maintaining stable coaxial positioning within the simple plate hole, eliminating the need for complex mechanical variable-angle mechanisms in the plate.
3Reliability
If the fastening element surface is made harder than the bone plate, then screw locking efficiency and resistance to metal chip production are improved, but manufacturing complexity increases
Solution Approach 1:
The invention applies local quality enhancement by selectively hardening only the critical surface regions of the screw that require high wear and chip resistance, such as the engagement surface and threading areas. The core material remains ductile and biocompatible. This can be achieved through surface treatments like nitriding, carburizing, or PVD/CVD coating, which create a hard surface layer while maintaining the bulk material's desirable properties, thus improving locking efficiency without requiring complex manufacturing of the entire screw.
4Ease of manufacture
If simple hole design is used in bone plate, then manufacturing costs and ease of manufacture are improved, but angle stability and locking reliability may be compromised
Solution Approach 1:
The invention extracts the angle stability and locking functionality from the plate hole and relocates it entirely to the screw head. The plate hole is simplified to a basic cylindrical or conical shape that is easy to manufacture with standard drilling or punching processes. All angle stability requirements are met by the screw head's internal geometry and locking mechanisms, which are designed to provide variable angle engagement while maintaining stable coaxial positioning.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides high angle stability, easy screw insertion and removal, reduced manufacturing costs, and improved biocompatibility, enabling efficient bone healing with a low risk of metal chip production and enhanced screw performance.
Implementation Method 1
a method for oxygen diffusion hardening to enhance surface hardness and corrosion resistance
Data Source
AI summary
The invention concerns a bone plate system comprising: a bone fastening element comprising a shaft with a first thread, the fastening element further comprising a head with a second thread on its outer surface, the outer surface having a first hardness; and a bone plate having a second hardness which is smaller than the first hardness, the bone plate comprising a through hole for receiving the bone fastening element. The head is oxygen diffusion hardened.