Dual Mobility Joint Implant Constant Diameter Ratio
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Solution Overview
Problem
Dual mobility hip prostheses experience dislocation and wear issues due to varying surface diameters and friction torque, leading to potential jamming and prosthetic failure, despite advancements in material quality.
Innovation Solution
A line of joint implant systems with a constant ratio of inner diameters between the fixation cup and mobile insert, optimizing the surface area ratio to reduce friction torque and wear, thereby minimizing dislocation and jamming risks by maintaining a consistent diameter ratio between the small and large articulations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the diameter of the surfaces in contact increases, then the friction torque increases, but the wearing is generated at the large articulation increases
Solution Approach 1:
The patent applies parameter changes by establishing a specific mathematical relationship between the outer diameter of the mobile insert and the inner diameter of the fixation cup (ratio between 1.1 to 3). This controlled parameter change optimizes the friction torque while minimizing wear debris generation at the large articulation, resolving the contradiction between sufficient contact area and wear reduction.
2Strength
If the thickness of the mobile insert is increased, then the breaking risk decreases, but the starting torque at the large articulation increases
Solution Approach 1:
The patent resolves this contradiction by controlling the thickness parameter of the mobile insert within specific limits. The thickness is optimized to provide sufficient mechanical strength and creeping resistance while maintaining an outer diameter that limits the starting torque at the large articulation, preventing excessive contact energy and potential sinking issues.
3Force
If the outer diameter of the mobile insert increases, then the friction torque at the large articulation increases, but the energy contact at the sinking increases
Solution Approach 1:
The patent applies parameter changes by establishing a controlled relationship between the outer diameter of the mobile insert and the inner diameter of the fixation cup (ratio between 1.1 to 3). This optimization reduces the friction torque at the large articulation and consequently decreases the energy contact at the sinking interface, preventing premature failure while maintaining adequate structural integrity.
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 constant diameter ratio significantly decreases dislocation phenomena and wear debris, enhancing the longevity of the prosthetic joint by reducing the energy required for large articulation activation and limiting the external surface area of the mobile insert, thus minimizing osteolyses and prosthetic failures.
Implementation Method 1
the friction torque increases. Thereby, more wearing is generated at the level of the large articulation, that is, between the mobile insert and the inner cavity of the fixation cup
Implementation Method 2
The two, small and large, articulations, are called dual mobility. The small articulation is involved in motions of small amplitude
Data Source
AI summary
A line of joint implant systems includes an implant including a cup to be affixed in one of the elements of the considered joint, defining a smooth inner cavity of substantially hemispherical shape. The implant also includes an insert, mobile within the inner cavity of the fixation cup and having its smooth outer surface intended to cooperate by ball-and-socket joint with the inner cavity, and defining in turn a smooth inner cavity of substantially hemispherical shape. The implant further includes a head or ball, solid with a second element of the joint, of spherical shape, intended to be received in the inner cavity of the mobile insert and to form a second ball-and-socket joint. The ratio of the inner diameter of the inner cavity of the fixation cup to the inner diameter of the inner cavity of the mobile insert is constant, whatever the diameter of the selected ball.