Semi-constrained Ankle Prosthesis Rotating Bearing Insert
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semi-constrained ankle prostheses lack the range of motion and stability to adequately mimic natural ankle kinematics, particularly in cases of soft tissue deficiency, leading to issues like polymer wear, impingement, and cold flow due to misalignment and limited articulation.
Innovation Solution
A semi-constrained ankle prosthesis design featuring a snap-locking mechanism with a retaining flange and locking tab that securely fastens the bearing insert to the tibial component, allowing rotation while resisting linear movement, thereby enhancing the range of motion and accommodating misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the bearing insert is locked in position relative to the tibial component in a semi-constrained ankle prosthesis, then stability is improved, but the range of motion is reduced
Solution Approach 1:
The locking mechanism transitions from a static fixed position to a dynamic system that allows rotation. The bearing insert is locked against linear movement but permitted to rotate relative to the tibial component, enabling the prosthesis to adapt between stability and range of motion based on functional requirements.
Solution Approach 2:
The locking mechanism is divided into separate functional elements: a retaining flange that prevents linear displacement and a locking tab that permits rotation. This segmentation allows independent control of stability and rotational freedom, resolving the contradiction between these two requirements.
2Reliability
If the bearing insert is locked to prevent linear movement, then polymer wear is reduced, but articulation freedom is limited
Solution Approach 1:
The system dynamically controls the bearing insert's degrees of freedom by allowing rotation while preventing linear movement. This selective freedom reduces polymer wear through stable positioning while maintaining sufficient articulation freedom for natural ankle kinematics including inversion and eversion.
3Adaptability or versatility
If the bearing insert allows rotation relative to the tibial component, then range of motion is improved, but positioning stability is reduced
Solution Approach 1:
The locking mechanism segments the constraints into two independent functions: the retaining flange provides positioning stability by preventing linear displacement, while the locking tab enables rotation. This segmentation allows the system to simultaneously achieve both positioning stability and rotational freedom.
4Manufacturing precision
If a snap-locking mechanism is used to fasten the bearing insert, then manufacturing precision is improved, but device complexity is increased
Solution Approach 1:
The locking mechanism is segmented into simple, discrete components (retaining flange and locking tab) that can be manufactured with standard precision. Each component performs a single function, making manufacturing and assembly straightforward despite the overall system's functional complexity.
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 design provides a more natural range of motion, including inversion and eversion, reduces clinical issues like polymer wear and impingement, and maintains radii congruency, improving the overall functionality and stability of the ankle prosthesis.
Implementation Method 1
A semi-constrained ankle prosthesis design featuring a snap-locking mechanism with a retaining flange and locking tab that securely fastens the bearing insert to the tibial component
Implementation Method 2
The bearing insert is locked in position relative to the tibia component in a semi-constrained ankle prosthesis
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A semi - constrained ankle prosthesis (10) includes a tibial component (12) configured to be coupled to a surgically-prepared surface of the distal end of a tibia, and a bearing insert (16) locked to the tibial component. The bearing insert is rotative relative to the tibial component and has an articular surface (26) formed in an inferior surface (52) thereof.