Modular Radial Head Implant with Polyaxial Fixation
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Solution Overview
Problem
Current radial head prosthetic systems lack a simple yet effective modular design with improved fixation elements and materials for articulating surfaces, particularly in adapting to various bone anatomies and providing stable alignment.
Innovation Solution
A modular endoprosthetic radial head implant comprising a cannulated body, a spherical-head screw, and an end cap with customizable radiused depression, which can be manufactured from biocompatible materials like hydrogel or titanium, allowing for polyaxial adjustment and secure fixation using a jam nut, enabling precise anatomical matching and alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a modular radial head prosthesis is designed with multiple components (end cap, body, screw), then adaptability to various bone anatomies is improved, but device complexity increases
Solution Approach 1:
The radial head prosthesis is divided into three separate modular components: an end cap with bearing surface, a body portion with intramedullary canal, and a screw with spherical head. These segments can be independently selected and combined to match various bone anatomies, providing adaptability while maintaining manageable complexity through standardized interfaces.
Solution Approach 2:
The body portion serves multiple functions: it provides the intramedullary anchoring structure, contains the spherical receptacle for the screw head, and forms part of the final articulating surface. This multi-functionality reduces the number of separate components needed, balancing adaptability with device simplicity.
2Reliability
If fixation elements are enhanced with multiple components and locking mechanisms, then reliability of fixation is improved, but ease of operation deteriorates
Solution Approach 1:
The screw and end cap are designed to assemble in a single straightforward operation where the screw is inserted through the body and the end cap is placed over the spherical head. The jam nut provides a simple locking mechanism that secures the assembly without requiring complex tools or multiple steps, maintaining ease of operation while ensuring reliable fixation.
3Adaptability or versatility
If the bearing surface is customized with different radius configurations, then adaptability to joint types is improved, but manufacturing precision requirements increase
Solution Approach 1:
The bearing surface geometry is incorporated into the separate end cap component rather than being part of the main body. This segmentation allows the end cap to be manufactured with high precision for specific radius configurations (single radius, dual radius, eccentric radius) while the body and screw can be produced with standard tolerances, reducing overall manufacturing complexity.
Solution Approach 2:
Different radius configurations are applied locally to the end cap bearing surface depending on the specific joint replacement requirement. The end cap can be manufactured with the appropriate radius profile (single, dual, or eccentric) tailored to the patient's anatomy and joint type, while other portions of the implant maintain standardized geometry.
Data Source
AI summary
A modular endoprosthetic radial head implant includes an end cap secured to a cannulated body held to bone by a fixation element. The fixation element supports the cannulated body on a resected radial bone end, for example. The fixation element of one embodiment features a threaded stem with a spherical head. The stem fits distally into the cannulated body and extends through a hole formed by the distal end of the cannulated body. The spherical head nests inside the cannulated body. Polyaxial alignment between the cannulated body and the fixation element is locked using a jam nut tightened inside the cannulated body. An end cap fits into place proximally on the cannulated body. The end cap is formed of a joint surface material to provide a bearing surface.