Toggle Lever Bone Screw Extension Device
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Solution Overview
Problem
Existing bone screw extension devices and screwdriver instruments in minimally invasive spine surgery lack a secure and easy-to-operate connection, making it difficult for surgeons to accurately position and maintain the screwdriver on the bone screw during procedures.
Innovation Solution
A toggle lever mechanism with pivotally connected lever arms, where the first lever arm is removably attached to the extension device and the second lever arm is supported on the screwdriver shank, allowing for manual adjustment to overcome a dead center and achieve a tilt-stable position, ensuring non-rotatable and secure mounting on the bone screw.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a screwdriver instrument is used with an extension device for a bone screw, then the surgeon can access the bone screw through the extension device, but the connection between the screwdriver instrument and the bone screw lacks operational security and stability
Solution Approach 1:
The screwdriver instrument incorporates a toggle lever mechanism with lever arms that can pivot between different positions. The first lever arm pivots relative to the extension device, and the second lever arm pivots relative to the shank, allowing the instrument to transition from a transport position to an operating position where the shank is forced against the bone screw, providing both ease of positioning and secure connection
Solution Approach 2:
The toggle lever mechanism utilizes arcuate paths of motion for the lever arms. The first lever arm has a pivot bearing point that moves along an arc relative to the extension device, and the second lever arm similarly moves along an arc relative to the shank, enabling smooth transition to the forced-position that ensures operational security
2Reliability
If the screwdriver instrument is designed to be securely connected to the bone screw, then operational stability is improved, but the device complexity increases due to additional mechanisms
Solution Approach 1:
The screwdriver instrument is divided into functional segments: a shank for insertion into the access channel, a toggle lever mechanism with first and second lever arms for securing the connection, and a tool application point for engaging the bone screw. This segmentation allows each component to perform its specific function while maintaining overall simplicity
Solution Approach 2:
The toggle lever mechanism acts as an intermediary between the shank and the tool application point. It mediates the connection by using the lever arms to force the shank against the bone screw, providing operational security without requiring direct complex coupling between all components
3Manufacturing precision
If the screwdriver instrument requires precise positioning on the bone screw, then manufacturing precision is improved, but the ease of positioning by the surgeon deteriorates
Solution Approach 1:
The toggle lever mechanism is designed to automatically force the shank into the correct position against the bone screw when the lever arms are actuated. The mechanical geometry of the toggle lever system self-adjusts to achieve precise alignment, eliminating the need for the surgeon to manually position the instrument with high precision
Solution Approach 2:
The manual dexterity requirement for precise positioning is replaced by a mechanical forcing mechanism. The toggle lever mechanism uses lever arm geometry and pivot points to mechanically force the shank into the correct position, substituting surgical skill with mechanical precision
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
Enables the screwdriver instrument to be easily and securely positioned on the bone screw through a single manual movement, allowing simultaneous manipulation of the extension device and bone screw, enhancing operational efficiency and stability during surgery.
Implementation Method 1
the first lever arm is elastically and longitudinally extendable, and that this longitudinal extensibility and a distance between the second pivot bearing point and the common articulation point of the lever arms are adapted to each other in such a way that when manually tilting the second lever arm in the direction of a parallel alignment with the axial longitudinal direction, a dead center is overcome
Data Source
AI summary
The invention refers to an extension device (1) for a bone screw (4) and to a screwdriver instrument (2) connectable to the extension device (1); it is proposed that the screwdriver instrument (2) comprises a toggle lever mechanism (62) having a first and a second lever arm (64, 66), which are pivotally connected to each other through a common articulation point (68), that the first lever arm (64) may be removably applied, in the area of its free end (70), at a first pivot bearing point (72) on the extension device (1) and is pivotally mounted and axially supported in the applied state, and that the second lever arm (66) is pivotally mounted and axially supported at a second pivot bearing point (74) on the shank, that the first lever arm (64) is elastically and longitudinally extendable, and that this longitudinal extensibility and a distance between the second pivot bearing point (74) and the common articulation point (68) of the lever arms (64, 66) are adapted to each other in such a way that when manually pivoting the second lever arm (66) in the direction of a parallel alignment with the axial longitudinal direction (16), a dead center is overcome, and the toggle lever mechanism (62) reaches a tilt-stable position (60), in which the shank of the screwdriver instrument (2) is forced in the axial direction (16) against the tool application point of the bone screw.