Double Mobility Hip Prosthesis with Ceramic Liner
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Solution Overview
Problem
Double mobility hip prostheses face challenges in wear characteristics and fixation, particularly with the larger articulation of polyethylene liner against metal shell, which compromises stability and range of motion, and existing fixation methods are inadequate for patients with degraded acetabular bone tissue.
Innovation Solution
A prosthesis component featuring a shell made from fibre reinforced polymer material, such as carbon fibre reinforced polyether ether ketone (CFR-PEEK), with a ceramic liner and attachment means, providing ceramic on ceramic articulations and enhanced fixation through hydroxyapatite or porous metal coatings, and a circlip for retaining the femoral head.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a large diameter femoral head component is used to promote joint stability and increase range of motion, then stability and range of motion are improved, but the articulating surface area increases leading to increased wear damage
Solution Approach 1:
The prosthesis is divided into two articulating surfaces: a small diameter primary articulation between the femoral head and polyethylene liner for low wear, and a large diameter secondary articulation between the liner and metallic shell for stability and range of motion. This segmentation allows each articulation to be optimized for its specific function.
Solution Approach 2:
The polyethylene liner is nested within the metallic shell, creating a double mobility structure where the inner liner articulates with the femoral head while the outer shell provides additional stability. This nested configuration enables both small and large diameter articulations to coexist in the same prosthesis.
2Ease of manufacture
If conventional fixation methods (impact fixation or bone cement) are used for the metallic shell, then implantation is simplified, but fixation is inadequate for patients with degraded acetabular bone tissue
Solution Approach 1:
The shell material properties are changed by using porous metal or metal alloy with controlled porosity (20-80% pore volume). This parameter change enables bone ingrowth through the porous structure, providing biological fixation that is superior to impact fixation or bone cement for patients with degraded bone tissue.
Solution Approach 2:
The shell is made from composite or alloy materials with porous structure (such as porous titanium or titanium alloys) that combine mechanical strength with bone ingrowth capability. This composite approach provides both ease of implantation and reliable long-term fixation through osseointegration.
3Reliability
If an additional stationary liner is inserted to cover screw heads in double mobility prosthesis, then fixation is improved, but the space available for the femoral head is reduced
Solution Approach 1:
Screws are implanted into the shell before the liner is inserted, allowing the liner to be positioned over the screw heads without requiring an additional stationary liner. This preliminary action of screw insertion enables direct liner placement while maintaining both fixation strength and range of motion.
Solution Approach 2:
The liner is designed to be mobile and articulating rather than static, allowing it to move and articulate with the femoral head while covering the screw heads. This dynamic design maintains the full range of motion by enabling the liner to follow the femoral head's movement trajectory.
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 solution offers improved wear resistance and stability with reduced metal ion production, increased range of motion, and secure fixation options suitable for patients with degraded bone tissue, leveraging ceramic and fibre reinforced polymer materials for low wear and boundary lubrication.
Implementation Method 1
leveraging ceramic and fibre reinforced polymer materials for low wear and boundary lubrication
Data Source
Figure 1~2
Figure 3~4
AI summary
A prosthesis component 2 is disclosed, the component comprising a shell (2) formed form a carbon fibre reinforced polymer material and having an inner bearing surface (10); and a liner (6) formed from a ceramic material and having an outer bearing surface(12); wherein the liner (6) is received in an articulating manner within the shell (4). A hip replacement prosthesis is also disclosed, the hip replacement prosthesis comprising a prosthesis component (2) as disclosed and a femoral head prosthesis component (24), the femoral head prosthesis component being formed from a ceramic material.