Rocker Slide Lock for Spinal Bone Fastener Security
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Solution Overview
Problem
Existing surgical instruments used in spinal procedures face challenges in securely locking bone fasteners, leading to potential inadvertent disengagement during manipulation, which can compromise the stability of spinal constructs.
Innovation Solution
The introduction of a surgical instrument featuring a rocker slide lock mechanism that includes a collar and spring actuation tab, preventing the head-locking projection from disengaging by limiting pivotal motion when locked, and allowing disengagement when the collar is in a second position, maintaining a minimum profile during engagement and disengagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional locking mechanism is used without the rocker slide lock, then the device structure is simpler, but the head-locking projection can inadvertently disengage during manipulation
Solution Approach 1:
The collar is positioned in advance to engage with the actuation tab before any manipulation occurs, creating a pre-locked state that prevents inadvertent disengagement. The spring is pre-loaded to maintain constant pressure on the collar, ensuring continuous monitoring and control of the locking state.
Solution Approach 2:
The collar acts as an intermediary element between the actuation tab and the head-locking projection. It translates the binary state of the actuation tab into a continuous control mechanism, providing intermediate positioning options and smooth transition between locked and unlocked states.
2Reliability
If the collar is positioned under the actuation tab to limit pivotal motion, then the head-locking projection is secured, but the profile of the instrument increases
Solution Approach 1:
The collar is designed to be movable rather than fixed, allowing it to dynamically adjust its position between two extreme states (under the actuation tab for locking, and away from the tab for unlocking). This dynamic positioning enables the instrument to maintain a compact profile during operation while providing secure locking when needed.
Solution Approach 2:
The collar is received within the body member, nesting the locking mechanism within the existing instrument structure. The actuation tab is integrated into the rocker assembly, creating a compact nested arrangement that minimizes the overall profile while maintaining the necessary locking functionality.
3Strength
If the rocker assembly is made elongated to provide adequate lever arm, then the mechanical advantage is improved, but the device complexity and profile increase
Solution Approach 1:
The rocker assembly utilizes rotational motion about a fulcrum point to convert linear force application into rotational leverage. This dimensional transformation allows an elongated lever arm to provide mechanical advantage without increasing the linear profile of the instrument, as the rotation occurs within a compact radial space.
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
This solution effectively reduces the likelihood of inadvertent disengagement of bone fasteners, enhancing the stability and security of spinal constructs during surgical procedures, thereby improving the reliability of spinal fixation techniques.
Implementation Method 1
a spring actuation tab at one end of the arm in proximity to the body member
Implementation Method 2
a portion of the collar when under the actuation tab limits pivotal motion of the rocker assembly
Data Source
AI summary
A surgical instrument includes a body member and a leg having a first end integrated with and extending from the body member. A head cavity is in the leg portion to hold a head. A channel is formed along a longitudinal length of the leg. An elongated rocker assembly includes an elongated lever arm coupled within the channel about a fulcrum and a spring actuation. A projection of the arm projects in a direction of the head cavity. A rocker slide lock has a collar slidably coupled around the body member and having a first position located between the body member and the actuation tab, such that a portion of the collar is under the actuation tab to limit pivotal motion of the rocker assembly, and a second position having a clearance from under the actuation tab.