Injectable Bioresorbable Polymer Fastener for Bone Attachment
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Solution Overview
Problem
Current methods for attaching bioresorbable plates to bone, such as using screws, tacks, or ultrasonically inserted pins, are technique-sensitive, cause surgeon fatigue, risk thermal necrosis, and require multiple fasteners and reloading, which are time-consuming and inefficient.
Innovation Solution
A bone support attachment device that heats a bioresorbable polymer to flow and harden in place, forming a fastener without the need for tapping or individual heating, using a motor-driven plunger and cannula system that allows for continuous fastener formation without reloading, with temperature control to prevent tissue damage and varying dimensions for strength and fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If screws are used to attach bioresorbable plates to bone, then the attachment method is well-established, but the process is technique-sensitive and requires threading which increases complexity and risk of improper insertion
Solution Approach 1:
The invention extracts the threading operation from the fastener insertion process. Instead of threading the screw into the bone, a separate tap is first inserted to create the threaded hole, then the screw is inserted without threading. This separates the hole creation from the fastener insertion, simplifying the actual screw insertion process and reducing technique sensitivity.
Solution Approach 2:
The invention introduces a tap as an intermediary tool that creates the threaded hole before the screw is inserted. This intermediary device prepares the bone structure to receive the screw, eliminating the need for the screw itself to be threaded and reducing the complexity of the screw insertion process.
2Ease of operation
If manual screwdrivers are used to insert screws, then precision control is maintained, but surgeon fatigue increases with multiple screw insertions
Solution Approach 1:
The invention replaces the manual mechanical screwdriver system with a powered driving mechanism. The fastener is inserted using a powered device that automatically provides the necessary torque and driving force, eliminating surgeon fatigue while maintaining precision through controlled power delivery and standardized fastener interfaces.
3Productivity
If powered screwdrivers are used to speed insertion, then surgeon fatigue is reduced, but screws may be stripped or torque off the screw head
Solution Approach 1:
The invention extracts the threading function from the screw, creating a smooth-shafted fastener that is driven into a pre-threaded hole. This eliminates the threaded portion of the screw that is susceptible to stripping, while the separate tap ensures proper thread formation in the bone, maintaining reliability during powered insertion.
Solution Approach 2:
The tap serves as an intermediary that creates the threaded interface in the bone, allowing the smooth fastener to be reliably driven in without threads on the fastener itself. This separation protects the fastener from torque-related damage while the tap ensures proper thread creation.
4Strength
If standard bioresorbable screws are used, then the design is simple, but the shear strength is insufficient for load bearing applications
Solution Approach 1:
The invention segments the fastening function into two separate components: a tap that creates the threaded hole and provides load-bearing capacity through bone threads, and a smooth fastener that provides shear strength through its solid shaft design. This segmentation allows each component to be optimized for its specific function, with the smooth fastener having superior shear strength compared to threaded screws.
5Ease of operation
If tacks or rivets are used instead of screws, then insertion is simpler without threading, but pull out resistance is reduced
Solution Approach 1:
The tap acts as an intermediary that creates threaded engagement in the bone, providing the pull-out resistance that would otherwise require threads on the fastener itself. This allows the use of a simple smooth fastener design while achieving the pull-out resistance of threaded fasteners through the separately created bone threads.
6Device complexity
If cannulated pins are heated and deformed in place, then tapping is obviated, but additional time is required for individual heating of each fastener
Solution Approach 1:
The invention inverts the conventional sequence by creating the threaded hole first using a tap, then inserting the smooth fastener without heating or deformation. This reverses the approach of heating and deforming the fastener in place, achieving the goal of obviating tapping while eliminating the time-consuming individual heating step through a different sequence of operations.
7Ease of operation
If ultrasonically inserted pins are used, then tapping is not required and insertion is simple, but thermal necrosis risk increases at the polymer-bone interface
Solution Approach 1:
The invention replaces the ultrasonic heating mechanism with a mechanical tapping system that creates the threaded hole without thermal energy. The smooth fastener is then inserted mechanically without ultrasonic vibration, eliminating the source of thermal necrosis while maintaining insertion simplicity through the pre-created hole.
8Adaptability or versatility
If multiple fasteners of varying lengths and diameters are kept in inventory, then different case requirements are met, but significant space is required to house the inventory
Solution Approach 1:
The invention creates a universal fastener system where a single smooth fastener design can be used with various taps to create appropriately sized threaded holes. The smooth fastener itself does not vary in thread configuration since it has no threads, providing universality across different fastener sizes while reducing inventory complexity and storage requirements.
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 method reduces surgeon fatigue, minimizes thermal necrosis risk, allows for efficient and strong fastener formation with reduced inventory needs, and provides improved pullout resistance by aligning polymer molecules, enhancing the overall efficiency and safety of the bone attachment process.
Implementation Method 1
heating a bioresorbable polymer to a temperature at or above its glass transition temperature to soften the polymer
Implementation Method 2
a motor-driven plunger is used to expel the heated polymer through an injection cannula into a drilled hole in the bone
Implementation Method 3
The expelled polymer cools and hardens in place, forming a fastener
Implementation Method 4
provides improved pullout resistance by aligning polymer molecules
Data Source
AI summary
Methods and devices are shown for forming polymer fasteners into bone by expelling the polymer from a cannula. Devices and methods shown allow a user to form multiple fasteners of various sizes without re-loading a device. Devices and methods shown further provide temperature profiles during fastener formation that reduce or eliminate thermal necrosis. Devices and methods shown further provide fasteners with increased strength.