Acetabular Cup Collar Geometry for Stable Bone Cement Anchoring
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Solution Overview
Problem
Conventional acetabular prostheses face issues with unstable anchoring due to difficult bone cement access and steep wall thickness variations, leading to reduced range of motion and potential luxation.
Innovation Solution
A bionic acetabular prosthesis with annular collars having trapezoidal cross-sections and notches on its outer surface, allowing bone cement to fill and stabilize the prosthesis, while minimizing surface defects and enabling secure anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transverse and vertical grooves are formed in the outer surface of the cup body, then the prosthesis can be anchored to the acetabulum, but bone cement cannot access the grooves due to large mesa structures, resulting in unstable anchoring
Solution Approach 1:
The patent inverts the conventional groove design by creating collars with grooves on their inner surface rather than outer surface. This allows bone cement to access the grooves from the inside, enabling stable anchoring while maintaining manufacturability. The collars are formed with grooves that open inward, reversing the traditional outward-opening groove configuration.
Solution Approach 2:
The patent divides the cup body into multiple collars (first collar, second collar, third collar) with grooves formed between adjacent collars. This segmentation creates multiple access points for bone cement while distributing the anchoring function across several localized structures, improving both cement access and anchoring stability.
2Reliability
If transverse and vertical grooves are formed in the outer surface of the cup body, then the prosthesis can be anchored, but steep wall thickness variations occur around the grooves, requiring large wall thickness to prevent surface unevenness, which reduces range of motion
Solution Approach 1:
By inverting the groove location from outer surface to inner surface of the collars, the patent eliminates the steep wall thickness variations that would otherwise occur at the outer surface. The grooves are formed between collars on the inner surface, allowing for more gradual wall thickness transitions and reducing the minimum wall thickness required to prevent surface unevenness.
Solution Approach 2:
The patent applies different wall thickness characteristics to different regions of the collars. The collars have varying thicknesses at different locations (e.g., thicker at certain areas for structural integrity, thinner at others for range of motion), optimized locally rather than uniformly, allowing the minimum wall thickness to be reduced while maintaining structural integrity.
3Reliability
If collars with grooves are formed on the cup body, then stable anchoring can be achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The cup body is segmented into multiple collars (first, second, and third collars) that can be formed as separate features. This segmentation allows each collar to be optimized independently and can facilitate modular manufacturing or assembly processes, potentially reducing overall manufacturing complexity despite the increased number of features.
Solution Approach 2:
The patent specifies particular parameters for the collars including groove depth (0.1-2.0 mm), collar height (0.5-3.0 mm), and collar thickness (1.0-5.0 mm). By optimizing these parameters within specific ranges, the design achieves stable anchoring while maintaining manufacturability, as the parameters are within capabilities of standard manufacturing processes.
Data Source
AI summary
A bionic acetabular prosthesis has a spherically cap-shaped cup body. The body is inwardly concave at the bottom to form a hollow cavity, and has on its outer wall surface, annular collars, each having a trapezoidal cross-section with a larger base portion and a smaller top portion. The collars are provided with circumferentially-spaced notches, having a recessed depth smaller than or equal to a raised height of the collars. Slopes of opposite side faces of the cross-sectionally trapezoidal collars on the cup body avoid the formation of defects in the surface of the hollow cavity, ensuring good quality of the resulting acetabular prosthesis. In addition, notches may be arbitrarily formed in the collars. These notches interact with bone cement to restrict circumferential rotation of the cup body. Gently sloped surfaces of adjacent collars join and define annular grooves, which contain more bone cement, stabilizing the cup body.