Spinal Screw With Resilient Pawl Prevents Migration
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Solution Overview
Problem
Existing implant plate systems in spinal and orthopedic surgery face issues such as inadequate fixation due to false-locking of screws, screw loosening post-surgery, and the need for multiple steps and tools for secure fixation, which can lead to user error and screw migration causing injury.
Innovation Solution
A plate system with a screw featuring a resilient pawl that engages with a channel in the plate to prevent axial and rotational movement, ensuring secure retention and reducing the need for auxiliary components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional screw locking mechanism is used in implant plate systems, then the screw can be inserted and fixed into the plate, but the screw may experience false-locking, loosening, or migration due to inadequate fixation
Solution Approach 1:
The locking mechanism transitions from a static threaded connection to a dynamic ratchet-pawl system that allows controlled movement in one direction (screw insertion) while preventing movement in the opposite direction (screw backout). The pawl freely moves during insertion but engages with ratchet teeth to lock the screw in place, providing reliable fixation through dynamic mechanical action rather than static threading alone
Solution Approach 2:
The pawl acts as an intermediary component between the screw and the plate's ratchet mechanism. This intermediate element translates the rotational motion of the screw into a unidirectional locking action, mediating the interaction between the driving screw and the restraining plate structure to achieve reliable fixation
2Reliability
If multiple steps and tools are used for secure screw fixation, then the screw can be locked into the plate, but the process increases the risk of user error and requires additional tools and fixtures
Solution Approach 1:
The screw mechanism is designed to be self-locking through the ratchet-pawl system. As the screw is rotated into the plate, the pawl automatically engages with the ratchet teeth to prevent backout, eliminating the need for separate locking steps or additional tools. The system serves itself by incorporating the locking function directly into the screw-plate interaction
Solution Approach 2:
The insertion and locking functions are merged into a single integrated mechanism. The act of inserting the screw simultaneously activates the locking action through the ratchet-pawl engagement, combining what would traditionally require separate steps (insertion, locking, verification) into one unified operation that reduces procedural complexity
3Device complexity
If a simple screw-plate connection is used, then the device structure remains simple, but the screw may migrate axially or rotationally causing injury
Solution Approach 1:
The ratchet mechanism employs asymmetric tooth geometry where the ratchet teeth have a slope that allows pawl engagement in one direction but permits free movement in the insertion direction. This asymmetric design creates inherent directional control, preventing harmful screw backout and migration while maintaining structural simplicity through the geometric configuration rather than complex mechanical components
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 system effectively prevents screw migration and loosening, enhancing fixation reliability and reducing the risk of injury by providing a simpler, more secure locking mechanism that eliminates the need for additional tools and fixtures.
Implementation Method 1
A plate system with a screw featuring a resilient pawl that engages with a channel in the plate to prevent axial and rotational movement
Data Source
AI summary
Spinal fusion system and method utilizing an implant and screw, wherein at least one pawl is mounted on or integral with the screw to prevent said plate or screw from moving in at least one of an axial direction or a rotational direction.