Artificial Joint with Variable Curvature Radius for Natural Motion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional artificial joints fail to replicate the natural bending and stretching paths of human joints, leading to limited range of motion, loosening, and damage due to shape mismatches and excessive mechanical stress.
Innovation Solution
The artificial joint features a bone head portion with a curved surface defined by a curve that decreases in diameter toward the bending side, allowing for enhanced range of motion and smooth bending and stretching movements. This design includes a bone fossa portion made of metal, which reduces thickness while maintaining strength, preserving ligaments and tendons.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional anatomical shape artificial joint is mass-produced, then manufacturing cost is reduced and productivity is improved, but the range of motion is limited due to shape mismatches with individual patients
Solution Approach 1:
The invention applies parameter changes by varying the curvature radius of the bone head portion based on the rotation angle. Specifically, the curvature radius is smaller at rotation angles closer to the maximum range of motion and larger at smaller rotation angles. This continuous parameter variation allows the artificial joint to maintain appropriate contact geometry across the entire range of motion, resolving the contradiction between mass production (standardized manufacturing) and individualized performance (range of motion).
Solution Approach 2:
The invention implements dynamics by making the curvature radius of the bone head portion variable rather than fixed. The curvature radius changes dynamically with the rotation angle, being smaller when the rotation angle is close to the maximum range of motion and larger when the rotation angle is small. This dynamic geometric adaptation enables the artificial joint to reproduce natural joint movement paths while maintaining manufacturing feasibility through standardized production methods.
2Device complexity
If the bone head portion has a large curvature radius, then the structure is simpler and easier to manufacture, but the range of motion is limited and cannot reproduce natural joint paths
Solution Approach 1:
The invention resolves this contradiction by changing the curvature radius parameter based on the rotation angle. Instead of using a single large curvature radius throughout, the curvature radius is varied: it is smaller when the rotation angle is close to the maximum range of motion and larger when the rotation angle is small. This parameter variation enables the bone head portion to guide the bone fossa portion along the natural joint movement path while maintaining manufacturing simplicity through standardized production techniques.
3Ease of manufacture
If ligaments and tendons are excised during surgery to implant the artificial joint, then the implantation is simpler, but the joint function cannot be maintained and recovery is delayed
Solution Approach 1:
The invention applies the copying principle by replicating the natural joint's geometric characteristics in the artificial joint design. The bone head portion is designed with a curved surface whose curvature radius varies with rotation angle, copying the movement path of natural joints. This geometric copying enables the artificial joint to function naturally without requiring excision of ligaments and tendons, as these soft tissues can be preserved and continue to guide joint movement along the reproduced natural path.
4Ease of operation
If an integrated type artificial joint with flexible member is used, then the joint portion can bend, but it cannot hold the force upon bending and has low durability
Solution Approach 1:
The invention applies composite materials by combining a metal bone head portion with a resin bone fossa portion. The metal bone head portion provides the necessary strength and rigidity to hold forces during bending, while the resin bone fossa portion allows for smooth bending motion. This composite construction resolves the contradiction between bending capability and force holding capability, as each material contributes its advantageous properties to the overall joint performance.
Data Source
AI summary
An artificial joint is characterized by: having a first member including a caput part on which a prescribed curved surface is formed, and a second member including a fossa part having a surface which abuts the prescribed curved surface of the caput part; the second member being rotatable in a flexing direction of a joint with a prescribed point on the caput part being the center of rotation; and the prescribed curved surface of the caput part being defined by a curve which depicts a convex arc toward the side abutting the fossa part when the caput part is viewed from the axial direction of the rotation, and in which, when two arbitrary points are taken on the curve, the radius of curvature of the point positioned further toward the flexing side of the joint on the curve is smaller than the radius of curvature of the other point.