Acetabular Liner Anti-Rotation Keys for Secure Installation
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Solution Overview
Problem
Current modular orthopaedic surgical implant systems face challenges in securely and efficiently aligning and installing acetabular bearing components with respect to acetabular shell components, which can affect the stability and longevity of the prosthetic joint.
Innovation Solution
The proposed solution involves an acetabular prosthesis assembly with an acetabular shell component featuring a tapered surface and anti-rotation slots, and an acetabular bearing component with anti-rotation keys and a flange that engages with the shell component's tapered surface, allowing for rotational alignment and secure installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional acetabular liner installation methods are used, then the installation process is simple, but rotational alignment precision and mechanical interlock are insufficient
Solution Approach 1:
The patent employs asymmetric anti-rotation keys with specific geometries that match corresponding asymmetric slots in the acetabular shell. This asymmetric design ensures precise rotational alignment by allowing the bearing component to rotate only to the correct orientation where the keys engage with the slots, eliminating rotational misalignment while maintaining a relatively simple overall device structure.
Solution Approach 2:
The patent utilizes a tapered surface with curved geometry on the bearing component that interfaces with a corresponding tapered receptacle in the shell. This curved/tapered design provides self-aligning characteristics during installation, guiding the bearing into the correct rotational position through the geometric constraint of the tapered surfaces, thereby improving alignment precision without complex adjustment mechanisms.
2Reliability
If anti-rotation keys are added to the bearing component, then mechanical interlock and resistance to dislocation are improved, but the device structure becomes more complex
Solution Approach 1:
The patent divides the anti-rotation function into discrete segments by incorporating multiple separate anti-rotation keys around the circumference of the bearing component. Each key independently engages with a corresponding slot, providing distributed mechanical interlock points. This segmentation enhances reliability by ensuring that dislocation resistance is maintained even if one key-slot interface experiences stress, while the modular key design keeps the added structural complexity manageable.
Solution Approach 2:
The anti-rotation keys are integrated into the bearing component structure in a nested manner, where the keys are formed as part of the bearing's overall geometry rather than being separate external attachments. This nesting approach provides the necessary mechanical interlock functionality while minimizing additional structural complexity, as the keys utilize the existing bearing material and geometry.
3Manufacturing precision
If the flange is designed to contact the tapered surface only when aligned, then rotational alignment is enforced, but the installation process becomes more difficult
Solution Approach 1:
The patent incorporates a tapered lead-in surface on the bearing component that guides the installation process. During installation, this tapered surface makes initial contact with the corresponding tapered receptacle in the shell, automatically guiding the bearing into the correct rotational alignment before the flange reaches the final contact position. This preliminary guiding action enforces rotational alignment while simplifying the installation process by eliminating the need for manual alignment adjustments.
Solution Approach 2:
The tapered surfaces with curved geometries provide self-aligning characteristics during installation. The curved/tapered interface allows the bearing component to be inserted at various angles and automatically guides it into the correct rotational position through geometric constraint, making alignment enforcement inherent to the design rather than requiring complex adjustment procedures.
Data Source
AI summary
An acetabular prosthesis assembly includes an acetabular shell component and an acetabular bearing component. The shell component includes a concave inner wall having a tapered surface with multiple anti-rotation slots defined therein. The bearing component includes a convex outer wall as well as an annular flange and multiple anti-rotation keys extending radially outward from the outer wall. When the anti-rotation keys are positioned in rotational alignment with the anti-rotation slots, the flange of the bearing component is positioned in contact with the tapered surface of the shell component. When the anti-rotation keys are positioned out of rotational alignment with the anti-rotation slots, the flange is spaced apart from the tapered surface. Methods for assembling and using the acetabular prosthesis assembly are also disclosed.