Spinal Persuader with Auto-Locking Ratchet for Rod Alignment
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Solution Overview
Problem
Current spinal fixation systems face challenges in effectively repositioning vertebral bodies to align with fixation rods, particularly in maintaining the adjusted position of one vertebral body while adjusting adjacent vertebrae, and preventing the spreading of components during the procedure.
Innovation Solution
The persuader instrument features a housing with a longitudinal passage, first and second arms with detents for detachable connection to vertebral implants, an auto-locking ratchet assembly, and anti-splaying elements to securely advance and lock the fixation rod into a polyaxial screw assembly, ensuring precise alignment and maintaining the adjusted position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a persuader instrument is used to reposition vertebral bodies, then alignment with fixation rod is improved, but components may spread apart during the procedure
Solution Approach 1:
The patent applies preliminary anti-action by incorporating anti-splaying elements that preemptively counteract the spreading force before it can cause misalignment. The distal anti-splaying elements are positioned to resist outward forces on the arms, while the anvil provides a counteracting force to maintain component cohesion during the persuasion process
Solution Approach 2:
The patent implements preliminary action by pre-positioning the anti-splaying elements and anvil to maintain component stability before the actual alignment maneuver. The biasing element is pre-loaded to provide continuous radial force that keeps the arms constrained, preventing spread before it can occur during vertebral body repositioning
2Manufacturing precision
If vertebral bodies are repositioned sequentially, then alignment with fixation rod is improved, but maintaining adjusted position of one vertebral body while adjusting adjacent vertebrae is difficult
Solution Approach 1:
The patent applies self-service through the auto-locking ratchet assembly that automatically maintains the adjusted position of each vertebral body. Once a vertebral body is repositioned, the ratchet mechanism self-locks to hold the alignment, allowing the surgeon to proceed to adjacent vertebrae without needing to continuously maintain the previous adjustment
Solution Approach 2:
The patent uses the ratchet assembly as an intermediary mechanism between the vertebral body adjustment and the final fixed position. The ratchet acts as a mediator that captures and maintains the adjusted position, enabling sequential adjustment of multiple vertebrae while preserving each individual adjustment
3Ease of operation
If distal ends of arms are allowed to move towards each other, then rod reduction is facilitated, but components may spread apart
Solution Approach 1:
The patent applies preliminary anti-action by positioning the distal anti-splaying elements to counteract any spreading force that may arise during rod reduction. These elements are pre-positioned to resist outward movement of the arms, allowing the distal ends to move toward each other for rod reduction while preventing any unintended spreading
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 persuader instrument enables precise repositioning and alignment of vertebral bodies with fixation rods, maintaining the adjusted position and preventing component spreading, thereby facilitating effective spinal correction and alignment.
Implementation Method 1
biased in the direction of the threaded rod by a biasing element applying a radial force
Implementation Method 2
a ratchet assembly that allows axial displacement of the shaft in a first direction and that prevents axial displacement of the shaft in a second direction
Data Source
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AI summary
A persuader instrument (100) for advancing a fixation rod into a vertebral implant includes a housing (110) and at least one arm (122). The at least one arm can include detents (126) for detachable connection to the vertebral implant. The persuader instrument also includes a shaft (140) coupled to an anchor (150). The anchor includes a fixation rod engagement surface. The shaft is axially displaceable through the housing to axially displace the anchor and a rod engaged by the anchor. The persuader instrument further includes an auto-locking ratchet assembly (160) in releasable engagement with the shaft. The auto-locking ratchet assembly controls axial displacement of the shaft through the longitudinal passage of the housing.