Orthopaedic Head Alignment Guide for Axial Taper Assembly
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Solution Overview
Problem
Existing orthopaedic joint prostheses face challenges in ensuring secure assembly without exceeding force limits, which can damage patient bone tissue or components, particularly with modular designs using self-locking tapers.
Innovation Solution
An alignment guide that engages the assembly surface of a joint prosthesis head part, allowing controlled application of assembly force along a defined axis, using a reference for alignment and incorporating features like bearing surface seating members and pivoting arms to facilitate secure engagement and minimize damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sufficient force is applied to ensure proper engagement of tapered surfaces, then assembly security is improved, but damage to bone tissue or components may occur
Solution Approach 1:
The alignment guide acts as an intermediary device between the impacting rod and the prosthesis components. It includes a bore that receives the impacting rod and a recess that receives the head part, with the bore axis aligned to the recess axis. This intermediary structure ensures that impact force is transmitted along a precise axis, preventing misalignment and excessive lateral forces that could damage bone tissue or components while still achieving secure engagement.
Solution Approach 2:
The alignment guide is positioned and aligned before the actual impact assembly operation. The bore of the alignment guide is pre-aligned with the axis of the head part recess, establishing the correct force transmission path in advance. This preliminary alignment ensures that when impact force is applied through the alignment guide, it follows the optimal path for secure assembly without causing damage.
2Reliability
If maximum force limit is exceeded to ensure proper engagement, then assembly reliability is improved, but damage to patient bone tissue occurs
Solution Approach 1:
The alignment guide serves as a protective intermediary that mediates between the impacting rod and the prosthesis components. Its structured bore and recess configuration ensures that impact forces are transmitted along a precise, pre-established axis, preventing excessive lateral or misaligned forces from reaching the bone tissue. This intermediary structure allows sufficient force to be applied for reliable assembly engagement while protecting against bone tissue damage through controlled force direction.
3Manufacturing precision
If alignment precision is improved using an alignment guide, then assembly accuracy is improved, but device complexity increases
Solution Approach 1:
The alignment guide is segmented into distinct functional elements: a bore for receiving the impacting rod, a recess for receiving the head part, and an alignment feature that ensures the bore axis coincides with the recess axis. This segmentation allows each element to perform its specific function while maintaining overall simplicity. The modular design achieves precise alignment without requiring complex mechanisms.
Solution Approach 2:
The alignment guide is a relatively simple intermediary device that adds minimal structural complexity while significantly improving assembly accuracy. Its straightforward design with a bore and recess provides effective alignment functionality without the need for complex adjustment mechanisms or multiple components, thus balancing precision improvement with device complexity.
Data Source
AI summary
An orthopaedic joint prosthesis assembly includes a head part of an orthopaedic joint prosthesis component and an alignment guide. The head part has a spherical bearing surface for articulation with a corresponding joint surface, and an assembly surface having a first bore formed in it for receiving a spigot on another part of the orthopaedic joint prosthesis. The bore has a first axis that extends perpendicular to the assembly surface. The alignment guide has an axial portion defining a second axis and an arm extending from the axial portion. The arm includes a distal portion which is configured to engage the assembly surface, with the axial portion being arranged to engage the bearing surface of the head part when the head part is mounted within the guide such that an impaction force applied along the second axis is directed along the first axis.