Polymeric Shoulder Implant Head with Taper Adaptor
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Solution Overview
Problem
Existing shoulder joint implants transfer significant stress to bone and soft tissue, require extensive bone resection, and experience high wear between components, limiting fixation and postoperative procedures.
Innovation Solution
A shoulder implant assembly featuring a humeral stem, a polymeric head with a metal substrate, and a taper adaptor, which reduces weight, minimizes bone resection, and enhances fixation through a polymeric cover and anti-rotation features, allowing for reduced wear and improved articulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If traditional metal head and UHMWPE bearing are used, then the implant provides sufficient strength and wear resistance, but the weight is high causing increased stress on bone and soft tissue
Solution Approach 1:
The patent applies composite materials by combining a metal substrate (cobalt-chrome or titanium alloy) with a polymeric cover (UHMWPE or vitamin E stabilized polyethylene). This composite head structure reduces overall weight compared to solid metal while maintaining strength through the metal substrate and wear resistance through the polymeric bearing surface.
Solution Approach 2:
The head is segmented into two functional parts: a metal substrate providing structural strength and a polymeric cover providing low-friction bearing surface. This segmentation allows each material to optimize its specific function while reducing total implant weight.
2Ease of operation
If traditional shoulder implant design is used, then the implant provides stable articulation, but extensive bone resection is required during implantation
Solution Approach 1:
The patent changes the geometric parameters of the head, specifically offering different head heights (anatomical and non-anatomical options) and shapes. This allows surgeons to select optimal head dimensions that reduce the need for extensive bone resection while maintaining stable articulation and fixation.
3Device complexity
If traditional modular connection is used, then the implant allows for assembly flexibility, but wear between components increases
Solution Approach 1:
The taper adaptor is nested within the head assembly, creating a compact modular connection system. The adaptor features a tapered bore that receives the head and a corresponding tapered outer surface that interfaces with the stem or glenoid, providing secure fixation while maintaining assembly flexibility.
Solution Approach 2:
The taper adaptor serves as an intermediary component between the head and the stem/glenoid. This mediator provides a precise tapered interface that reduces micromotion and wear between the modular components while maintaining assembly flexibility.
4Weight of moving object
If the head is made entirely of polymeric material, then the weight is reduced and wear is minimized, but the structural strength and durability are compromised
Solution Approach 1:
The patent uses composite materials with a metal substrate providing structural strength and a polymeric cover providing low weight and wear resistance. This composite construction resolves the contradiction between weight reduction and strength maintenance.
Solution Approach 2:
Different regions of the head have different material properties: the metal substrate provides localized structural strength where needed, while the polymeric cover provides localized wear resistance and low friction at the articulating surface.
Data Source
AI summary
A shoulder implant assembly including a humeral stem, a head, a cup, and a taper adaptor. The humeral stem is configured to be inserted into a humerus bone. The head includes a metal substrate having a coupling taper and a polymeric cover mounted to the metal substrate having a convex outer surface and a generally planar base. The cup has a concave surface configured to articulate with the polymeric cover of the head. The taper adaptor is configured to mate with the coupling taper of the head. The taper adaptor is configured to connect the head to the stem when the cup is connected to a glenoid. The taper adaptor is configured to connect the head to the glenoid when the cup is connected to the humeral stem.