Cervical Screw Inserter with Rotational and Translational Locks
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Solution Overview
Problem
Existing screw inserters for spinal screws are prone to accidental uncoupling due to soft tissue interference and often have complex, bulky designs that can lead to issues during cervical spine procedures.
Innovation Solution
A screw inserter with a simple actuation mechanism that allows 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, ensuring secure screw insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing screw inserters are used, then screw insertion function is provided, but accidental uncoupling occurs due to soft tissue interference causing rotation and unthreading
Solution Approach 1:
The inserter is divided into distinct functional segments: an outer element with threaded distal end for engaging the coupling element, and an inner element with distal end for engaging the screw portion. This segmentation allows independent optimization of each component's function and reduces interference from soft tissue during insertion.
2Reliability
If locking mechanisms are added to prevent uncoupling, then reliability improves, but device complexity and bulk increase
Solution Approach 1:
The locking mechanism is merged into the basic structural components of the inserter. The outer and inner elements themselves serve as the locking structure through their geometric engagement features, eliminating the need for separate, complex locking devices. The coupling between elements is achieved through integrated geometric features rather than additional components.
3Reliability
If complex locking mechanisms are implemented, then rotational locking is achieved, but inner element tips become susceptible to breaking due to uneven torque loading
Solution Approach 1:
The inner element is designed with varying local properties: a reduced diameter section provides flexibility and stress distribution, while the distal engaging portion maintains sufficient strength. The geometric engagement features are positioned to distribute torque loading evenly along the inner element, preventing stress concentration at the tip.
4Measurement precision
If multiple actuation mechanisms are added for locking, then control precision improves, but ease of operation deteriorates due to complicated procedures
Solution Approach 1:
The inserter employs passive translation mechanisms where the inner element automatically translates along the outer element through its own geometric features and spring-loaded buttons, without requiring active actuation by the operator. The system self-regulates the locking and unlocking processes through its inherent mechanical design, reducing the operator's burden while maintaining precise control.
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 inserter provides a user-friendly, streamlined operation that prevents accidental uncoupling and simplifies cervical spine procedures by ensuring secure engagement and disengagement of spinal screws.
Implementation Method 1
The button includes a spring-loaded button
Implementation Method 2
a ramped surface on the inner element configured to enable passive translation of the inner element with respect to the outer element
Implementation Method 3
an outer element, including a threaded distal end for engaging a coupling element of the screw
Data Source
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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.