Flexible Screw Manipulation Tool With Guide Rod Torque Control
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Solution Overview
Problem
The manipulation of flexible fastening devices, such as bone screws, is hindered by twisting issues when using traditional screwdrivers, and there is a need for a mechanism to easily insert, remove, or adjust screws, especially in curved orientations like bone cavities, where the distal portion of a broken screw requires removal.
Innovation Solution
A tool assembly comprising a flexible guide rod with a proximal threaded section, a mid-section, and a distal tapered end, along with a handle sub-assembly, allows for the insertion, removal, and manipulation of fastening devices by engaging the guide rod with the screw's internal cavity, enabling torque transmission and alignment without excessive rotation, using materials like Nitinol, spring steel, or flexible polymers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional screwdriver is used to manipulate flexible fastening devices, then the screwdriver can engage with the drive recess of the screw, but twisting issues occur during manipulation
Solution Approach 1:
The tool is divided into two separate functional components: a guide rod that extends through the fastening device to provide distal support and prevent twisting, and a handle sub-assembly that provides proximal engagement for manipulation. This segmentation allows each component to specialize in its function, with the guide rod preventing twisting and the handle enabling operation.
Solution Approach 2:
The guide rod acts as an intermediary element that transmits mechanical stability from the distal end of the fastening device back to the operator. By extending through the fastening device and engaging with the handle sub-assembly, it mediates between the manipulation forces applied proximally and the structural integrity required distally, preventing twisting during insertion and adjustment.
2Ease of operation
If a traditional screwdriver is used, then the drive shaft can rotate the screw, but excessive rotation occurs making precise control difficult
Solution Approach 1:
By separating the rotation function (handle sub-assembly) from the support function (guide rod), the system allows controlled rotation at the proximal end while maintaining structural stability at the distal end. This enables precise rotational control during screw insertion and positioning.
Solution Approach 2:
The guide rod serves as a mediator that limits excessive rotation by providing a stable reference axis through the fastening device. It transmits rotational control from the handle while preventing uncontrolled twisting, thereby maintaining alignment precision during manipulation.
3Power
If the guide rod is made rigid, then torque transmission is efficient, but the tool cannot navigate curved orientations like bone cavities
Solution Approach 1:
The guide rod is designed with dynamic properties, being flexible rather than rigid, allowing it to adapt to curved anatomical structures like bone cavities. The flexibility enables the guide rod to navigate complex orientations while still providing sufficient structural support for torque transmission during screw manipulation.
Solution Approach 2:
The physical parameters of the guide rod are optimized by selecting materials and dimensions that provide appropriate flexibility. The guide rod's flexibility parameter is tuned to allow navigation of curved paths while maintaining enough stiffness to transmit torque effectively for screw insertion and adjustment.
4Reliability
If the guide rod extends through the entire fastening device, then distal support is provided, but the tool complexity increases
Solution Approach 1:
The tool is segmented into two main components (guide rod and handle sub-assembly) that work together to provide distal support. This segmentation allows the guide rod to extend through the fastening device for stability while keeping each component's design relatively simple and focused on its specific function.
Solution Approach 2:
The guide rod serves multiple functions: providing distal support to prevent twisting, serving as a guide for screw insertion, and transmitting mechanical forces from the handle to the distal end of the fastening device. This multi-functionality reduces the need for additional components, thereby limiting overall tool complexity.
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
Facilitates efficient insertion, removal, tightening, and loosening of flexible screws in curved orientations, including broken screws, by allowing rotation at both ends and preventing twisting, thus enhancing the handling of flexible fastening devices in medical and other applications.
Implementation Method 1
The flexible guide rod (120) is comprised of a proximal threaded section (121), a mid-section (123), and a distal section (125)... The material for the flexible guide rod can be selected from the group consisting of Nitinol, spring steel, flexible polymers and flexible composites
Implementation Method 2
The outward taper is about 1 degree for a Morse taper fit and less than 90 degrees for a non-Morse taper fit... The tapered internal surface (166) of the distal end (156) of the fastening device (150) is tapered to the same degree as the distal tapered section (125) to enable the two elements to engage with one another
Data Source
AI summary
A tool for manipulating flexible and non-flexible fastening devices. The tool assembly has a flexible rod for insertion into the distal end of the fastening device. A handle assembly interacts with proximal end of the flexible rod and the proximal end of the fastening device to control of the fastening device by initiating rotation at the distal end of the fastening device.