Variable Stiffness Prosthetic Trunnion via Additive Manufacturing
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Solution Overview
Problem
Current prosthetic implants, particularly those with modular designs, face issues such as trunnionosis due to wear, corrosion, and mechanical insufficiency at the trunnion interface, leading to increased revision rates and complications like metal ion release and fretting damage.
Innovation Solution
The implementation of additive manufacturing techniques, such as 3D printing, to create prosthetic components with variable stiffness profiles that mimic the mechanical properties of natural bone, including angularities and differential stiffness, to enhance alignment and reduce micro-motion and corrosion, along with controlled material properties and support systems to prevent fractures and improve osteo-integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If modular design is introduced to allow customization of leg length and offset, then adaptability and ease of operation are improved, but wear and mechanical insufficiency at the trunnion interface increase leading to trunnionosis
Solution Approach 1:
The patent applies parameter changes by modifying the geometric parameters of the trunnion interface, specifically introducing non-circular cross-sectional profiles (such as oval, rectangular, or polygonal shapes) instead of traditional circular profiles. This changes the contact mechanics and stress distribution at the interface, reducing wear and preventing trunnionosis while maintaining the modular design's adaptability for customization of leg length and offset.
Solution Approach 2:
The patent employs composite materials by combining different metal alloys at the modular junction (e.g., cobalt chrome femoral head on Titanium trunnion) and using material composition changes to reduce corrosion and fretting. The use of biocompatible metal alloys with different properties creates a composite structure that resists wear and corrosion while maintaining mechanical strength.
2Adaptability or versatility
If different metal alloys are used at the modular junction under high loads, then adaptability is improved, but corrosion and fretting damage increase
Solution Approach 1:
The patent changes the material parameters by selecting specific metal alloy combinations (such as cobalt chrome and Titanium) with complementary properties that resist galvanic corrosion. The parameter change also includes modifying the surface characteristics through anodization or other surface treatments to reduce fretting damage while maintaining the adaptability of the modular junction configuration.
Solution Approach 2:
The patent uses composite materials by creating a multi-material construction at the modular junction, combining dissimilar metal alloys (cobalt chrome femoral head on Titanium trunnion) that are selected for their complementary corrosion-resistant properties. This composite material approach reduces galvanic corrosion and fretting damage while maintaining the mechanical strength required for high-load bearing.
3Manufacturing precision
If traditional machining techniques are used for trunnion production, then manufacturing precision is maintained, but wear patterns and micro-motion increase
Solution Approach 1:
The patent applies parameter changes by transitioning from traditional circular cross-sectional profiles to non-circular profiles (oval, rectangular, polygonal) through advanced manufacturing techniques. This parameter change in geometry reduces micro-motion and wear patterns while maintaining manufacturing precision through computer-controlled fabrication processes such as additive manufacturing or precision machining of non-circular forms.
Solution Approach 2:
The patent substitutes traditional subtractive machining methods with additive manufacturing (3D printing) or other advanced fabrication techniques to produce non-circular trunnion profiles. This mechanical system substitution enables complex geometries that reduce wear and micro-motion while maintaining or improving manufacturing precision through digital control of the fabrication process.
Data Source
AI summary
A system and method for improving mechanical assemblies, such as prosthetic implants, intended to be installed in living tissue such as bone. Force-imparting devices are adapted and may include angularity, which may be introduced with specialized additive manufacturing, which may impart congruent cross-sections while providing variable stiffness. In some cases, the variable stiffness may be “stretchy” in a longitudinal direction and “rigid” in a radial directional which may provide an assembly bias. Additive manufacturing may allow the material of a prosthesis to be varied (e.g., density/porosity) to create variable stiffness over a length.