Variable-Inclination Humeral Head Assembly With Interference-Fit Stud
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Solution Overview
Problem
Current shoulder, elbow, and hip arthroplasty systems lack the ability to provide a physiologically accurate range of inclination and version for humeral components, leading to component malposition and requiring complex assembly methods that are inefficient and difficult to implement.
Innovation Solution
A joint prosthesis system with a humeral head assembly featuring a mounting stud and adapter that allows for variable inclination and version adjustment through an interference fit, utilizing a taper to secure the components in place, enabling precise alignment and simplifying the assembly process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple fixed inclination stems are manufactured to provide variable inclination, then the range of inclination is improved, but the inventory complexity and device complexity increase significantly
Solution Approach 1:
The prosthesis is divided into two independent components: a stem and a humeral head assembly. The stem remains fixed while the humeral head assembly can be configured with different inclination angles through the mounting stud mechanism. This segmentation allows variable inclination to be achieved without manufacturing multiple inclined stems, thereby reducing inventory complexity while maintaining adaptability.
Solution Approach 2:
The mounting stud is designed to allow dynamic adjustment of the humeral head assembly's inclination angle relative to the stem. The stud can be positioned at different angles and locked in place, enabling the surgeon to select the optimal inclination angle for each patient without being constrained to fixed pre-set angles, thus providing versatility without requiring multiple stem variants.
2Adaptability or versatility
If a set screw is used to lock the inclination angle, then the inclination can be adjusted, but the reliability decreases as the set screw becomes the weak link
Solution Approach 1:
The mounting stud is designed to be extractable from the stem, allowing the entire humeral head assembly to be removed as a unit without compromising the stem or requiring damage to surrounding structures. This eliminates the need for set screws that could become weak links, as the retention mechanism relies on the interference fit and geometric constraints of the stud and stem opening rather than a separate fastening element.
3Reliability
If a lateral opening screw is used to fix inclination, then the inclination is locked, but the ease of operation deteriorates as stem removal becomes impossible without head removal
Solution Approach 1:
The mounting stud is designed as a separate, removable component that connects the humeral head assembly to the stem. This segmentation allows the humeral head assembly to be detached from the stem independently, enabling stem removal or revision without necessarily removing the entire prosthesis. The stud can be accessed and manipulated through the lateral opening to facilitate this independent removal capability.
4Reliability
If complex assembly with locking mechanism is used, then the inclination is secured, but the device complexity and ease of operation worsen due to more than ten assembly steps
Solution Approach 1:
The mounting stud combines multiple functions into a single component: it provides inclination adjustment, inclination locking, and mechanical connection between the stem and humeral head assembly. By merging these functions into one element rather than using separate adjustment mechanisms and locking devices, the assembly process is simplified to fewer steps while maintaining reliable inclination securing.
Solution Approach 2:
The mounting stud's geometry and interference fit with the stem create a self-locking mechanism. Once the stud is inserted at the desired inclination angle, the interference fit and geometric constraints automatically secure the position without requiring additional locking steps or complex assembly procedures. The design self-services the locking function through its inherent structural properties.
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
Enables accurate and efficient adjustment of humeral component inclination and version, reducing inventory needs and simplifying surgical procedures while ensuring anatomically correct placement, applicable to shoulder, elbow, and hip arthroplasty.
Implementation Method 1
The mounting stud has a first end with a spherical bearing surface and a second end configured to be secured to a prosthesis stem by way of an interference fit formed by impacting the mounting stud in a stem opening
Implementation Method 2
utilizing a taper to secure the components in place, enabling precise alignment and simplifying the assembly process
Data Source
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AI summary
Methods and devices are disclosed for joint (e.g., shoulder) arthroplasty. In one aspect, there is provided a device for determining inclination and/or version of a prosthetic head with respect to a prosthetic stem. In another aspect, there is provided a joint (e.g., shoulder) prosthesis. In another aspect, there is provided a method for setting an inclination angle and/or a version angle of a prosthetic head with respect to a stem implanted or to be implanted in a bone of a joint (e.g., shoulder).