Expandable Tibial Trial Screw Mechanism
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Solution Overview
Problem
Current knee arthroplasty trial systems are time-consuming and complex due to the need for multiple trials to find the proper fit, especially with discrete fixed-height trials being difficult to insert and remove, and shim systems requiring numerous components and being complicated to assemble.
Innovation Solution
An expandable tibial trial with a screw-driven ramp mechanism that allows for discrete thickness settings, featuring a helical cut actuation screw and expansion ramp, providing tactile and visual feedback for optimal sizing, and a modular articular insert trial that snaps onto the expandable tibial trial, reducing the number of components and simplifying the trialing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If discrete fixed-height trials are used, then the implant size can be evaluated, but the trialing process becomes time-consuming and difficult to insert and remove
Solution Approach 1:
The trial insert is designed with an expandable structure that can dynamically change its thickness. The top plate can be adjusted to different heights relative to the bottom plate using a screw mechanism, allowing the insert to be expanded or collapsed. This dynamic adjustment capability eliminates the need for multiple discrete fixed-height trials, as a single trial insert can be adjusted to match various insert thicknesses, thereby reducing the time required for the trialing process while maintaining precise implant size evaluation.
2Adaptability or versatility
If multiple discrete trials are used to cover all tibial/femoral sizes and insert thicknesses, then complete sizing coverage is achieved, but the device complexity and number of components increases
Solution Approach 1:
The trial insert is designed as a universal component that can serve multiple functions by adjusting its thickness. The expandable mechanism allows a single trial insert to replace multiple discrete trials of different thicknesses. The top plate can be positioned at various heights to simulate different insert thicknesses, enabling one trial insert to evaluate multiple sizing scenarios. This multi-functionality reduces the total number of trial components needed while maintaining comprehensive sizing coverage.
Solution Approach 2:
The trial insert employs a nested structure where the top plate can be collapsed onto the bottom plate when not in use. The expandable and collapsible design allows the trial insert to be compacted to a minimal profile for easy storage and handling, while still providing the capability to expand to various thicknesses during the trialing process. This nesting principle reduces the space required for storing multiple trial inserts and simplifies the overall device configuration.
3Length of moving object
If shim systems are used to increase the height of the stack, then the insert thickness can be adjusted, but the assembly becomes complicated and time-consuming
Solution Approach 1:
Instead of using separate shim components that require assembly, the trial insert incorporates an integrated dynamic adjustment mechanism. The screw thread engagement between the adjustment screw and the ramp allows for smooth, continuous adjustment of the top plate height. This dynamic mechanism eliminates the need to assemble multiple shims, providing a simpler and more intuitive operation for adjusting insert thickness while maintaining the ability to achieve various height configurations.
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 expandable tibial trial system significantly reduces the number of instruments needed, enhances efficiency by allowing single-trial expansion to desired heights, and provides clear feedback for optimal sizing, thereby streamlining the knee arthroplasty trial process.
Implementation Method 1
The actuation screw defines a helical cut with step portions, and the expansion ramp includes a pin configured to engage the helical cut of the actuation screw. When the actuation screw is rotated, the pin rides along the helical cut and is configured to rest within one of the step portions
Implementation Method 2
an expansion ramp configured to slide along the bottom plate and lift the top plate as the ramp translates forward
Data Source
AI summary
Knee arthroplasty trials, systems, and methods regarding the same. The knee arthroplasty trial system may include an expandable tibial tray trial having top and bottom plates, an actuation screw retained in the bottom plate, and an expansion ramp configured to slide along the bottom plate and lift the top plate as the ramp translates forward. The actuation screw may define a helical cut with step portions, and the expansion ramp includes a pin configured to engage the helical cut of the actuation screw. When the actuation screw is rotated, the pin rides along the helical cut and is configured to rest within one of the step portions, thereby ensuring that the expandable tibial tray trial expands only to discrete thicknesses.