Magnesium Bone Screw Design for Breakage Resistance
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Solution Overview
Problem
Magnesium alloy bone screws are prone to breakage and difficult to align during implantation due to their softness and design limitations, which affects their corrosion resistance, biodegradability, and biocompatibility, necessitating an improved design for medical applications.
Innovation Solution
A biodegradable magnesium-containing bone screw with a thicker head, non-threaded pointed tip, and a shaft design that includes a transition from non-threaded to threaded sections, enhancing alignment and torque resistance, and made from alloys like magnesium, iron, zirconium, manganese, and calcium, which provide corrosion resistance and biocompatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnesium alloy is used for bone screws to achieve biodegradability and corrosion resistance, then biocompatibility and tissue regeneration are improved, but the material becomes softer and more prone to breakage during implantation
Solution Approach 1:
The patent changes the compositional parameters of the magnesium alloy by incorporating specific alloying elements (Al, Zn, Ca, Fe, Mn) in controlled amounts to modify the material's mechanical properties while preserving biodegradability. This resolves the contradiction by adjusting material parameters to achieve both softness for biodegradability and sufficient strength for implantation.
Solution Approach 2:
The patent creates a composite magnesium alloy system combining multiple elements (Mg-Al-Zn-Ca-Fe-Mn) to achieve properties that pure magnesium cannot provide. The composite structure provides both the desired biodegradability and improved mechanical strength, resolving the contradiction between these two properties.
2Strength
If magnesium alloy bone screws are designed with conventional dimensions to maintain structural integrity, then strength is improved, but alignment and placement become difficult during implantation
Solution Approach 1:
The patent applies local quality changes by creating a thicker head portion specifically at the top of the screw shaft where alignment and torque application are needed, while maintaining the original shaft dimensions. This localized structural modification improves ease of operation during implantation without compromising the overall structural integrity of the screw.
Solution Approach 2:
The patent segments the screw structure into distinct functional zones: a thicker head portion for alignment and torque resistance, a standard shaft portion for insertion, and a threaded section for bone engagement. This segmentation allows each part to be optimized for its specific function, resolving the contradiction between strength and ease of operation.
3Ease of operation
If magnesium alloy screws are made with thicker heads to reduce breakage and improve alignment, then ease of operation is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses parameter changes in the form of controlled alloying and thermal processing to achieve the thicker head geometry without requiring complex multi-step manufacturing processes. By adjusting material composition and heat treatment parameters, the desired geometry and mechanical properties are achieved through material science rather than complex manufacturing, thus avoiding increased device complexity.
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 improved design reduces breakage and facilitates easier placement, maintaining biodegradability and corrosion resistance, allowing for effective tissue regeneration and minimizing surgical removal needs in orthopedic, craniofacial, and cardiovascular surgeries.
Implementation Method 1
magnesium degrades to produce a soluble, non-toxic corrosion hydroxide product which is harmlessly excreted through urine
Implementation Method 2
capable of degrading, e.g., corroding, over time in a physiological environment
Data Source
AI summary
The invention relates to a biodegradable, magnesium-containing bone screw for implanting into a patient body for use in medical applications, such as, orthopedic, craniofacial and cardiovascular surgery. The bone screw has a head, shaft and tip. The thickness of the head is greater than the thickness of conventional bone screws. The shaft includes both a non-threaded and a threaded portion. The tip is non-threaded and pointed, such as, conical in shape. The composition of the bone screws provide for improved biodegradability and biocompatibility, and the features of the structure of the bone screws facilitate guidance and placement during implantation as well as reduce the potential for mechanical failures.