Reducer Handle Locking Mechanism With Pawl Feedback
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Solution Overview
Problem
Current rod reduction instruments in spinal fixation procedures face challenges such as binding due to misalignment, obstructed view, difficulty in determining rod reduction, and complex manufacturing of ratchet locks, which hinder efficient set screw insertion and usability.
Innovation Solution
A locking mechanism for reducer instruments featuring a pawl that travels with one handle to lock into a groove in the opposing handle, providing auditory and tactile feedback for sufficient rod reduction and allowing easy release with a button, eliminating the need for a large ratchet at the proximal end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large and long ratchet with multiple teeth is used at the proximal end of the opposed handles, then the locking mechanism can maintain the handles in position, but it becomes prone to binding due to misalignment and obscures the surgeon's view
Solution Approach 1:
The patent removes the traditional large ratchet mechanism from the proximal end of the handles and replaces it with a compact pawl and groove system located at the distal end near the pivot joint. This extraction of the locking function from its conventional location eliminates the binding and obstruction problems while maintaining the essential locking capability.
Solution Approach 2:
Instead of using a ratchet at the proximal end that locks by preventing separation of handles, the patent inverts the approach by placing a pawl at the distal end that locks into a groove on the opposing handle. This inversion of location and mechanism type resolves the binding issue while achieving the same functional goal of maintaining handle position.
2Reliability
If multiple ratchet teeth are used, then the locking mechanism can maintain handle position, but it becomes difficult to determine when the rod is sufficiently reduced for set screw insertion
Solution Approach 1:
The patent incorporates an auditory and tactile feedback mechanism where the pawl engages with a specific groove on the opposing handle to indicate that sufficient rod reduction has been achieved. This single clear engagement point provides unambiguous feedback to the surgeon, replacing the confusing multiple ratchet teeth engagement scenario.
3Reliability
If a large ratchet is disposed at the proximal end of the device, then locking can be achieved, but it interferes with gripping and actuation of the instrument
Solution Approach 1:
The patent extracts the locking mechanism from the proximal end where it interferes with gripping, and relocates it to the distal end near the pivot joint. This relocation allows the surgeon to grip the handles comfortably without the locking components obstructing the hand or interfering with the actuation motion.
4Reliability
If a ratchet lock with multiple teeth is used, then positioning can be maintained, but it is difficult to manufacture due to precision machining requirements
Solution Approach 1:
The patent segments the locking function into a simple pawl component and a groove feature, replacing the complex multi-tooth ratchet system. This segmentation into fewer, simpler components dramatically reduces manufacturing complexity while maintaining the position maintenance capability through the pawl-groove engagement.
Data Source
AI summary
Disclosed are reducer instrument locking mechanisms. They can be located near a center pivot joint of the reducer, thereby eliminating a ratchet at the reducer proximal end. The locking mechanisms can include a pawl or latch that travels with one handle from an open position to a closed position. The pawl can fall into a groove formed in an opposing handle such that handles of the reducer can be locked relative to one another, at least with regard to movement of the handles away from one another. When falling into the groove, the pawl can create an auditory and/or tactile indication that a sufficient amount of rod reduction has been achieved to allow for set screw insertion. After set screw insertion, the reducer locking mechanisms can be released to clear it of the groove and allow the reducer to return to its open position.