Bone Joint Implant Articulation Component Design
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Solution Overview
Problem
Current bone joint implants face challenges with limited mobility, leading to edge loading and impingement, and risk of separation due to inappropriate articulation and leverage, which can result in dislocation and reduced clinical outcomes.
Innovation Solution
The design incorporates an articulation component with a proximal saddle and an intramedullary stem, featuring a distally-facing recessed surface and enlarged lateral edge portions, forming a ramped or shoulder surface, which defines the limits of articulation and allows for a cone of motion exceeding 50°, reducing the risk of dislocation and enhancing mobility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the range of motion is increased to model natural joint motions, then clinical outcomes are improved, but the risk of edge loading and impingement increases
Solution Approach 1:
The articulation head is designed with a spherical geometry that articulates within a spherical recess in the intramedullary stem. This spherical configuration allows for multi-directional movement (flexion, extension, abduction, adduction) while maintaining continuous surface contact, thereby increasing range of motion without creating edge loading or impingement conditions.
Solution Approach 2:
The design changes the geometric parameters of the articulation surfaces, specifically using a spherical head with a radius of curvature that matches the spherical recess. This parameter matching ensures optimal contact across the entire articulation surface throughout the range of motion, preventing edge loading while maximizing mobility.
2Ease of operation
If the head and stem interaction is optimized for mobility, then range of motion is maximized, but the risk of separation due to leverage increases
Solution Approach 1:
The spherical head fitting within a spherical recess creates a self-centering mechanism that maintains stable articulation during movement. The curved surfaces ensure that forces are distributed across the contact interface, preventing lever arm effects that could cause separation or dislocation while preserving full mobility.
Solution Approach 2:
Instead of using a planar or constrained articulation surface that would prevent separation but limit mobility, the invention inverts the approach by using a spherical configuration that naturally prevents separation through its geometry while allowing maximum mobility. The spherical recess acts as a constraint that follows the head through its range of motion rather than restricting it.
3Adaptability or versatility
If a larger cone of motion is provided to enhance mobility, then natural joint-like movement is achieved, but the complexity of defining articulation limits increases
Solution Approach 1:
The spherical recess in the intramedullary stem naturally defines the articulation limits through its geometric boundaries. The spherical shape provides inherent articulation limits in all directions simultaneously, creating a well-defined cone of motion without requiring complex mechanical stops or constraints. The radius of the spherical recess directly determines the cone of motion angle.
Data Source
AI summary
An articulation component (1, 100) is for a bone joint hemiarthroplasty implant having an intramedullary stem (50) with a socket (53). The articulation component has a proximal saddle (2, 110) for non-engaging abutment with a proximal bone and a ball (4, 104) for engaging in the stem socket (53). The saddle has a distally facing recessed surface (10, 110) for engagement with the stem proximally facing surface (55) to define limits of articulation, in one case a cone of motion of about 60° with minimal risk of socket dislocation. Also, the saddle has an enlarged lateral-most edge portion (11, 111, 211) on two diametrically opposed sides of the neck, for conformity with a patients' anatomy.