Flexible Prosthesis Stem Lamellas for Bone-Sparing Insertion
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Solution Overview
Problem
Current prosthesis stems are inflexible and cause damage to surrounding bone tissue upon insertion, leading to instability and impaired osseointegration.
Innovation Solution
A prosthesis stem design featuring flexible lamellas that compress upon insertion, reducing bone damage and enhancing stability through a bending joint that allows for a more secure fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid surface structures are used in prostheses, then structural strength is maintained, but stress shielding and bone resorption occur due to insufficient stress transfer to the implant surface
Solution Approach 1:
The prosthesis surface is segmented into multiple lamellas (thin layers) with varying orientations and densities. This segmentation allows different regions to have different mechanical properties, enabling stress distribution across the implant surface while maintaining overall structural strength. The lamellar structure creates a gradient that facilitates stress transfer to the bone.
Solution Approach 2:
The prosthesis employs a composite structure combining rigid base material with flexible surface lamellas. This composite design allows the interior to provide structural strength while the flexible surface layers enable stress transfer and bone ingrowth, resolving the contradiction between strength and bone integration.
2Reliability
If flexible surface structures are used to enable bone ingrowth, then bone-implant integration improves, but structural strength and stability may be compromised
Solution Approach 1:
Different regions of the prosthesis surface have locally optimized properties: some areas have higher flexibility to promote bone ingrowth, while other areas maintain higher rigidity for structural support. This local differentiation allows simultaneous achievement of bone integration and structural strength.
Solution Approach 2:
The flexible lamellas are arranged in multiple orientations and layers, creating a three-dimensional stress distribution network. This dimensional complexity allows the structure to maintain strength through geometric configuration rather than relying solely on material rigidity.
3Ease of manufacture
If smooth implant surfaces are used, then manufacturing is simplified, but stress transfer to the implant surface is insufficient leading to stress shielding
Solution Approach 1:
The surface is segmented into lamellar structures that can be manufactured as integrated layers during the forming process. This segmentation provides stress-transfer capability without requiring complex post-processing, maintaining ease of manufacture while improving stress transfer.
4Reliability
If complex surface structures with varying lamella orientations are used, then stress distribution and bone ingrowth are improved, but device complexity increases
Solution Approach 1:
The lamellar structure serves multiple functions simultaneously: it distributes stress, promotes bone ingrowth, and can be manufactured as an integrated component. This multi-functionality reduces the need for additional separate features, offsetting the apparent complexity with functional consolidation.
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 flexible lamellas reduce the risk of bone damage and improve the stability of the prosthesis by matching the flexibility of the bone, ensuring a secure and stable implantation.
Implementation Method 1
Prostheses with flexible surface lamellas, in particular hip joint prostheses, have a prosthesis surface which has flexibility in the longitudinal direction of the prosthesis axis
Implementation Method 2
The flexible prosthesis surface promotes bone ingrowth and/or osteogenesis
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 3
AI summary
A prosthesis or implant device for use in joint or bone repair, or restoration of function. The prosthesis or implant device comprises a stem, in which a portion of the stem comprises non-overlapping lamellas around part or all of the circumference of the stem. Each lamella is connected to the external surface of the stem via a bending joint, which permits the space between the rest of the inner surface of the lamella and the external surface of the stem to decrease upon application of a force to the outer surface of the lamella. In addition, methods of treating a subject in need of joint replacement or bone repair using the prosthesis or implant device.