Bone Fixation Device with Expandable Strips for Transverse Load Transmission
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Solution Overview
Problem
Existing medical devices for fixing bone parts often fail to securely immobilize joints without causing bone damage or necrosis, and they can be difficult to insert during minimally invasive surgeries due to complexity and cost.
Innovation Solution
A medical device comprising a rigid outer tube with opposed recesses and a longitudinally extending inner tube with strips that bend outward under axial pressure, secured by a screw mechanism, allowing for transverse load transmission while preventing longitudinal movement and enabling insertion over a guide wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a screw is screwed into the femur head and slidily accommodated in a plate, then the device can transmit loads transversely to the longitudinal axis, but the femur head can rotate freely about the screw axis causing necrosis and the screw may damage the bone
Solution Approach 1:
The device is divided into separate functional components: a pin for insertion through the bone, expandable elements for securing against rotation, and a plate for external fixation. This segmentation allows each component to perform its specific function without causing the harmful effects of the conventional screw-plate combination.
Solution Approach 2:
Instead of using a screw that rotates into the bone and risks damaging it, the invention uses a pin that is inserted and then secured by expandable elements that prevent rotation. The fixation mechanism is inverted from internal screw fixation to external pin fixation with expandable locking elements.
2Reliability
If a pin is slidingly accommodated in a plate with expandable elements, then rotation can be prevented, but the expandable elements require complicated and costly means to be moved apart
Solution Approach 1:
The expandable elements are pre-configured on the pin in a collapsed state that allows easy insertion. The expansion mechanism is designed to be activated by a simple action (such as bending or breaking the pin) that automatically deploys the expandable elements without requiring complicated external actuation mechanisms.
Solution Approach 2:
The expandable elements are designed to automatically expand and lock into place through their own structural response to insertion forces or simple manual actions, eliminating the need for complex motorized or mechanically actuated expansion systems.
3Object-affected harmful factors
If a pin is driving rather than screwed into the bone, then bone damage is reduced, but the pin can easily move out of the femur head
Solution Approach 1:
The pin is segmented into functional zones: a insertion portion that can be driven into the bone, expandable elements that provide retention, and a plate attachment portion. This segmentation allows the pin to be driven without screwing (reducing bone damage) while the expandable elements provide the necessary retention to prevent displacement.
Solution Approach 2:
The physical state of the expandable elements changes from a collapsed insertion configuration to an expanded retention configuration. This parameter change (from compact to expanded state) enables the pin to be easily inserted and then securely retained in the bone without requiring screw threading.
4Ease of operation
If known devices are not hollow, then they cannot be inserted over a guide wire, but making them hollow would complicate the structure
Solution Approach 1:
The pin and its expandable elements are nested within a hollow cylindrical shell that can be inserted over a guide wire. The hollow structure allows the device to be delivered through a minimally invasive pathway guided by a wire, while the internal components (pin, expandable elements) are nested within this hollow casing.
Solution Approach 2:
The device is segmented into an outer hollow casing that provides the guide wire insertion capability and an inner pin assembly with expandable elements that provides the fixation function. This segmentation allows the hollow casing to be inserted over the guide wire while the inner components perform the bone fixation function.
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 device provides secure, cost-effective, and minimally invasive fixation of bone parts, preventing device displacement and facilitating healing by transmitting loads transverse to the longitudinal axis without risking bone damage or necrosis.
Implementation Method 1
means for loading the inner tube in axial direction are made up of a screw that fits in another end of the outer tube that is positioned in the bone, which screw mates with screw thread present on the inner wall of the outer tube
Implementation Method 2
the screw and the plate are rigid, to such an extent that the device is capable of transmitting loads
Implementation Method 3
a pressure force exerted on said strips causes the strips to bend outwards through the aforesaid recesses
Implementation Method 4
the strips to bend outwards through the recesses in the outer tube, wherein the end piece, in this case made up of a shoulder, can exert a pressure force on the strips, causing said strips to bend outwards
Implementation Method 5
the medical devices of the present kind are intended to take up and transmit a load in a direction substantially transversely to the longitudinal direction of the medical device
Implementation Method 6
A rigid outer tube, which is provided with at least two opposed recesses near the first end that is positioned in the bone
Data Source
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AI summary
A medical device for fixing bone parts or for fixing stabilizing elements to bone parts, comprising a rigid outer tube, which is provided with at least two opposed recesses on the side that is positioned in the bone, wherein a second inner tube is accommodated in said rigid outer tube, which inner tube is provided with at least two strips extending in the longitudinal direction of the inner tube on the side that is positioned in the bone, whilst means are provided for loading the inner tube in axial direction, in such a manner that a pressure force is exerted on said strips, which pressure force causes the strips to bend outwards through the aforesaid recesses.