Acetabular Bearing Liner Fixation With Deformable Locking Projection
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Solution Overview
Problem
Existing acetabular prostheses lack an efficient and secure mechanism for fixing a bearing liner within a shell, which can lead to potential disassembly and instability during implantation.
Innovation Solution
An acetabular prosthesis system with a shell and a bearing liner, where the liner features an axial fixation projection that deforms upon insertion into the shell, engaging a depression within the shell to create a secure, locked configuration, enhancing fixation and resistance to disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate fixation element is used to secure the bearing to the shell, then the bearing can be fixed in the shell, but the device complexity increases and the assembly process becomes more complicated
Solution Approach 1:
The fixation function is merged into the liner itself through the axial fixation projection, eliminating the need for separate fixation elements. The projection integrates the bearing fixation capability directly into the liner structure, simplifying the overall device while maintaining reliable fixation to the shell.
2Ease of operation
If the liner is inserted into the shell without a fixation mechanism, then the assembly process is simple, but the liner lacks rotational stability and may disassemble post-surgery
Solution Approach 1:
The liner performs its own fixation function through the axial fixation projection that automatically engages with the depression in the shell during insertion. This self-fixating mechanism eliminates the need for separate fixation tools or complex assembly procedures while ensuring rotational stability is achieved inherently through the design.
3Strength
If the axial fixation projection is made rigid, then the fixation strength is high, but the projection cannot deform to properly engage the depression during insertion
Solution Approach 1:
The fixation projection transitions from a flexible state during insertion to a rigid locked state after engagement. During insertion, the projection deforms elastically to navigate the engagement path and enter the depression. Once seated, the projection assumes a locked configuration that provides strong fixation resistance, achieving both ease of assembly and high fixation strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides strong lever-out and push-out forces, ensuring the liner remains securely fixed within the shell, meeting ASTM standards for resistance to disassembly, with forces ranging from 190 Nm to 258 Nm (140 ft/lb to 190 ft/lb) for lever-out and 434 Nm to 542 Nm (320 ft/lb to 400 ft/lb) for push-out.
Implementation Method 1
The axial fixation projection may be deformed by the internal surface of the shell during insertion of the liner into the shell
Implementation Method 2
The engagement portion of the liner may engage or be received by a depression formed within the shell. Once engaged with the depression the liner is substantially fixed to the shell
Data Source
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AI summary
Disclosed is a bearing liner (30) engageable within a shell member (20) with an integrated projection portion (90). The integrated projection portion may deform a selected amount during positioning of the bearing liner within the shell. The shell may include a complementary engaging portion (60).