Ratcheting Rod Reduction Instrument for Jam-Free Screw Removal
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Solution Overview
Problem
Existing rod reduction instruments for spinal fusion procedures face challenges with jamming during high reduction forces, requiring extraordinary measures like cutting the connecting rod to remove pedicle screws, and lack efficient dual-mode operation for quick and fine-tuning adjustments.
Innovation Solution
A ratcheting rapid rod reduction instrument with a dual-mode operation, featuring a ratchet mechanism that can switch between quick engagement/disengagement and fixed modes, utilizing a ratchet lock-out mechanism to overcome external forces and ensure easy removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional rod reduction instrument is used, then the instrument can engage the pedicle screw, but the instrument jams during high reduction forces requiring cutting the connecting rod to remove
Solution Approach 1:
The instrument incorporates a ratchet mechanism that allows dynamic switching between locked and unlocked states. The ratchet lever can be positioned to either engage with the ratchet teeth (locked state for high reduction forces) or disengage (unlocked state for easy removal), transforming a static instrument into a dynamic one that adapts to different operational phases.
Solution Approach 2:
The instrument changes its mechanical state parameters through the ratchet mechanism. By moving the ratchet lever between positions, the instrument transitions from a high-friction locked state that prevents jamming during reduction to a low-friction unlocked state that enables easy removal, effectively changing the friction and engagement parameters on demand.
2Measurement precision
If a rod reduction instrument operates in fixed mode only, then fine-tuning adjustments can be made, but quick engagement and disengagement are slow
Solution Approach 1:
The instrument provides dynamic mode switching between quick engagement (ratchet unlocked, outer housing slides freely) and fine-tuning (ratchet locked, outer housing fixed relative to inner sleeve). This transforms a static single-mode instrument into a dynamic dual-mode instrument that adapts to different operational requirements.
Solution Approach 2:
The instrument separates the engagement process into two distinct phases using the ratchet mechanism: a quick engagement phase where the outer housing slides rapidly over the inner sleeve, and a fine-tuning phase where the ratchet locks prevent further movement. This segmentation allows each phase to be optimized independently for speed and precision.
3Device complexity
If a rod reduction instrument lacks a ratchet mechanism, then the structure is simpler, but the instrument jams during high reduction forces
Solution Approach 1:
The ratchet mechanism acts as an intermediary element between the outer housing and inner sleeve. It provides a controlled friction interface that prevents jamming during high reduction forces by allowing incremental movement while maintaining engagement, without requiring a completely complex mechanical system.
Solution Approach 2:
The ratchet mechanism is self-regulating during operation. Under high reduction forces, the ratchet teeth automatically engage with the ratchet lever to prevent backward movement and jamming, without requiring external control or complex additional mechanisms. The mechanism serves itself by using the applied load to maintain proper engagement.
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 efficient and reliable rod reduction by allowing quick initial engagement and fine-tuning, preventing jamming and eliminating the need for cutting the connecting rod, thereby enhancing procedural efficiency and safety.
Implementation Method 1
The rod reduction instrument may include a ratchet mechanism that converts rotation of the top sleeve relative to the bottom sleeve to linear displacement of the inner sleeve
Implementation Method 2
The inner portion and outer portion may include complementary threading that engages one another
Data Source
AI summary
A rod reduction instrument includes an inner sleeve, a first housing portion, a second housing portion, a plurality of engagement members, and a ratchet mechanism. The inner sleeve can include a threaded proximal portion and a distal end. The first housing portion can be positioned over at least a portion of the inner sleeve. The second housing portion can be positioned proximate to the distal end of the inner sleeve. The plurality of engagement members can be adapted to receive a pedicle screw, and are positionable within the second housing portion. The ratchet mechanism can include an engagement feature to selectively engage the threaded proximal portion of the inner sleeve, and a locking mechanism to selectively lock the engagement feature of the ratchet mechanism against the threaded proximal portion of the inner sleeve.