Joint Socket Implant Toothing Anti-Rotation Mechanism
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Solution Overview
Problem
Existing joint socket implants face challenges in preventing rotation between the outer and inner shells, leading to potential damage and increased costs due to complex production processes and high pressing-in forces required for anti-rotation mechanisms, which can damage the inner shell and limit torque transmission.
Innovation Solution
A joint socket implant with a convex outer shell and concave inner shell featuring a circular toothing system with parallel flanks and a tooth profile defined by the difference between the radius of the tip circle and root circle, allowing for secure anti-rotation without damaging the softer inner shell material, while enabling stepless axial adjustment and efficient torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If penetration elements are used to prevent rotation of the inner shell, then anti-rotation is achieved, but production costs increase and the inner shell material may be damaged
Solution Approach 1:
The toothing system divides the anti-rotation function into multiple discrete teeth distributed around the circumferential region, rather than using a single complex penetration element. This segmentation allows the outer shell to be produced more easily while achieving reliable anti-rotation through the collective action of multiple teeth engaging with the inner shell's oversize region.
Solution Approach 2:
The patent uses a simpler toothing system that can be integrated into the outer shell production process without requiring expensive separate components. The teeth are designed to engage with the inner shell's oversize region, providing effective anti-rotation while minimizing production complexity and cost.
2Reliability
If spike-shaped penetration elements are used, then anti-rotation is achieved, but torque transmission is limited due to proximity to the central axis
Solution Approach 1:
The toothing system transitions from spike-shaped elements near the central axis to a circumferential distribution of teeth around the inner shell. This dimensional change from axial to circumferential arrangement significantly increases the lever arm for torque transmission while maintaining anti-rotation security through the engagement of multiple teeth with the oversize region.
3Reliability
If a toothing system with multiple teeth is used, then anti-rotation is achieved, but high pressing-in forces are required that can damage the inner shell
Solution Approach 1:
The patent optimizes the geometric parameters of the toothing system, including tooth profile, spacing, and engagement depth, to achieve effective anti-rotation with minimal pressing-in force. The oversize region of the inner shell is specifically designed to engage with the teeth, distributing the engagement forces across multiple contact points and reducing peak stresses that could damage the inner shell.
4Ease of operation
If the inner shell is made of softer material, then insertion is easier, but torque transmission capability is reduced
Solution Approach 1:
The solution employs a composite approach where the outer shell contains a toothing system that engages with the softer inner shell's oversize region. The outer shell's toothing provides the mechanical advantage for torque transmission, while the softer inner shell material facilitates easy insertion and engagement. This composite system combines the advantages of both material properties without sacrificing either insertion ease or torque transmission capability.
Data Source
AI summary
An outer shell (1) for a joint socket implant, in particular for an acetabular implant, which comprises a convex outer face (3) and a concave inner face (4) for receiving an inner shell. The concave inner face (4) has at least partially a toothing system (7), in particular a circular circumferential region (6) thereof. Via the toothing system (7), an inhibition of the rotatability of the two shells, relative to one another, can be achieved upon insertion of the inner shell into the outer shell (1).