Spinal Screw Inserter With Dual Locking for Stable Coupling
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Solution Overview
Problem
Existing screw inserters for spinal screws often catch on soft tissue during insertion, leading to accidental uncoupling and require complex, bulky designs that can break or actuate unintentionally, particularly in delicate cervical spine procedures.
Innovation Solution
A screw inserter with a simple actuation mechanism for rotational and translational locking of inner and outer elements, featuring a button and outer knob for controlled movement and a ramped surface for passive translation, along with various locking button configurations to prevent unwanted rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing screw inserters are used, then they can drive screws into vertebral bodies, but the outer elements can catch on soft tissue causing rotation and uncoupling from the screw
Solution Approach 1:
The inserter is divided into distinct functional elements: an outer element that engages the screw coupling element, and an inner element that engages the screw shaft. This segmentation allows independent optimization of each element's function, with the inner element providing stable screw engagement while the outer element provides controlled actuation, preventing soft tissue catching and uncoupling.
Solution Approach 2:
The inserter employs dynamic locking mechanisms that transition between locked and unlocked states. The first locking mechanism locks the inner element to the outer element during screw insertion, preventing accidental uncoupling. The second locking mechanism locks the outer element to the screw coupling element. These dynamic transitions allow the device to adapt its rigidity based on operational needs, providing stability when required and flexibility for actuation when needed.
2Reliability
If locking mechanisms are added to prevent uncoupling, then reliability improves, but the design becomes overly complicated and bulky
Solution Approach 1:
Multiple locking functions are merged into a coordinated system of two locking mechanisms. The first locking mechanism (between inner and outer elements) and the second locking mechanism (between outer element and screw coupling element) work together in a integrated manner, allowing the device to achieve reliable uncoupling prevention without requiring separate, complex locking systems for each function.
Solution Approach 2:
The outer element serves multiple functions: it engages the screw coupling element, provides the actuation interface for the surgeon, incorporates the second locking mechanism, and transmits rotational force to the screw. This multi-functionality reduces the need for additional separate components, simplifying the overall design while maintaining reliability.
3Reliability
If complex locking mechanisms are used, then uncoupling is prevented, but inner element tips become susceptible to breaking due to uneven torque loading
Solution Approach 1:
The torque transmission path is segmented through the two-stage locking system. The first locking mechanism transfers torque from the outer element to the inner element, while the second locking mechanism secures the outer element to the screw coupling element. This segmentation distributes torque loading more evenly across the structure, preventing concentration of stress at the inner element tip and reducing the risk of breakage.
Solution Approach 2:
The dynamic locking mechanisms allow the system to transition from a flexible state during assembly to a rigid locked state during torque application. When the locking mechanisms are engaged, they provide a stable, rigid connection that distributes torque evenly across the inner and outer elements, preventing uneven loading that could cause tip failure.
4Reliability
If multiple locking mechanisms are implemented, then rotational and translational locking is achieved, but the actuation mechanism becomes susceptible to being actuated by mistake
Solution Approach 1:
The actuation system is segmented into two independent control interfaces: a first actuation interface for the first locking mechanism and a second actuation interface for the second locking mechanism. This segmentation allows each locking mechanism to be controlled separately, reducing the risk of accidental actuation while maintaining secure locking when engaged. The surgeon can selectively engage or disengage each locking mechanism as needed.
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
Provides a user-friendly, streamlined operation that prevents accidental uncoupling and simplifies the insertion process, enhancing safety and reliability in spinal procedures.
Implementation Method 1
The button includes a spring-loaded button
Implementation Method 2
The tool includes a ramped surface on the inner element configured to enable passive translation of the inner element with respect to the outer element
Data Source
AI summary
A screw inserter for driving a screw into a vertebral body includes an inner element for engaging a screw portion of the screw and an outer element for engaging a coupling element of the screw. The outer element may include a threaded distal end. In addition, the screw inserter may include a button permitting the translation of the inner element with respect to the outer element. Further, the inserter may include an outer knob allowing the rotation of the inner element with respect to the outer element when moved to a first position. When the outer knob is moved to a second position it prevents the rotation of the inner element with respect to the outer element.