Radial Head Prosthesis Rotate-to-Lock Assembly
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Solution Overview
Problem
Current radial head prostheses face challenges in achieving optimal fit due to the need for a large inventory of sizes and configurations, and modular prostheses are difficult to assemble in situ, especially in the limited clearance of the elbow joint.
Innovation Solution
A radial head prosthesis system with a stem portion and a head portion that can be assembled by sliding the head onto the stem transversely and then rotated to create a frictional lock, eliminating the need for set screws and allowing assembly within the body, using a rotation interface with arcuate rails and channels to secure the head to the stem.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If modular radial head prostheses are used to allow independent optimization of head and stem, then adaptability is improved, but device complexity and difficulty of assembly increase
Solution Approach 1:
The prosthesis is divided into separate modular components: a stem portion and a head portion that can be independently selected and optimized for different patient anatomies and injury patterns, while still forming a unified functional implant system
Solution Approach 2:
The head portion is designed to be received within and nested onto the stem portion through a telescoping arrangement, where the head fits over the stem's arcuate rails that engage with channels in the head, creating a compact integrated structure from modular parts
2Ease of operation
If modular radial head prostheses are assembled outside the subject before insertion, then ease of operation is improved, but the ability to adjust in situ is lost
Solution Approach 1:
The stem portion is inserted into the patient's bone first, establishing the foundational component, and then the head portion is attached in a second step that can be performed with the stem already in position, allowing for intraoperative adjustments
Solution Approach 2:
The two-stage assembly process allows the stem and head to be prepared separately and then combined in situ, providing flexibility to adjust head positioning and configuration after the stem is securely implanted in the patient's anatomy
3Strength
If set screws are used to secure the head to the stem, then connection strength is improved, but device complexity and surgical time increase
Solution Approach 1:
The conventional set screw fastening mechanism is completely removed from the design, replacing it with a friction-based friction lock interface that achieves secure connection through surface friction and geometric interlocking rather than threaded fasteners
Solution Approach 2:
The friction lock interface creates a self-securing connection where the head portion automatically locks to the stem portion through friction forces generated during assembly and loading, eliminating the need for additional fastening components or steps
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
This solution enables secure attachment of the head portion to the stem portion without set screws, allowing for in situ assembly and potential reconfiguration, providing a stable and durable radial head replacement that can withstand biomechanical loads while minimizing surgical complexity.
Implementation Method 1
rotated with respect to the stem portion to produce friction that firmly attaches the head portion to the stem portion
Data Source
AI summary
System, including methods and apparatus, for replacing an end of a bone, such as a radial bone, with a prosthesis. In exemplary embodiments, the prosthesis is a radial head prosthesis having a stem portion and a head portion. The head portion may be configured to be (a) placed onto the stem portion by movement of the head and stem portions relative to one another transverse to a longitudinal axis of the stem portion, and then (b) rotated with respect to the stem portion to produce friction that firmly attaches the head portion to the stem portion.