Bone Anchor Coupling With Cam Locking for Fast Rod Adjustment
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Solution Overview
Problem
Existing polyaxial bone anchoring devices require complex and time-consuming adjustments for locking and unlocking the bone anchor and spinal rod during spinal surgery, necessitating a more efficient and user-friendly handling mechanism.
Innovation Solution
A coupling device with a receiving part and a pressure member, actuated by a rotational mechanism that transforms into a linear movement, allowing for quick and precise locking and unlocking of the bone anchor, facilitated by an instrument with a rotating shaft and cam portion, enabling temporary locking without obstructing the rod channel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyaxial bone anchoring device uses a traditional locking mechanism with multiple adjustment steps, then the bone anchor can be securely locked to the rod, but the surgical procedure becomes time-consuming and complex
Solution Approach 1:
The locking mechanism is segmented into distinct functional components: a pressure member for applying clamping force, an actuating portion for user input, and a cam portion for motion transformation. This segmentation allows each component to perform its specific function efficiently, enabling secure locking while reducing the number of adjustment steps required by the surgeon.
Solution Approach 2:
The mechanism transitions from a static traditional locking system to a dynamic cam-based system. The cam portion converts rotational movement into linear displacement of the pressure member, creating a dynamic locking action that is both quick to execute and secure once engaged. This dynamic approach reduces adjustment time while maintaining reliability.
2Reliability
If a polyaxial bone anchoring device uses a complex adjustment mechanism for locking and unlocking, then the bone anchor can be securely fixed, but the ease of operation during surgery is reduced
Solution Approach 1:
The cam portion acts as an intermediary between the user's rotational input and the pressure member's linear motion. This intermediary mechanism simplifies the user's task to a simple rotational movement while automatically generating the complex force distribution needed for secure locking, thereby improving ease of operation without compromising reliability.
Solution Approach 2:
The mechanism changes the parameter of motion from rotational (easy to perform) to linear (effective for locking). By transforming the type of movement required, the system makes the locking operation easier to perform while maintaining the security needed for reliable fixation.
3Reliability
If a polyaxial bone anchoring device uses a traditional locking mechanism, then the bone anchor is securely locked, but the ability to make repeated adjustments is reduced
Solution Approach 1:
The locking mechanism is designed to be periodically engageable and disengageable through simple rotational movements of the actuating portion. This periodic capability allows surgeons to make repeated adjustments to the bone anchor position while maintaining secure locking when the final position is achieved, thereby improving adjustment flexibility without sacrificing reliability.
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 repeated, easy adjustments of the bone anchor and rod position with minimal effort, allowing for improved surgical correction steps and flexibility in rod placement, enhancing surgical efficiency.
Implementation Method 1
the actuating portion includes a cam portion and the pressure member follows the movement of the cam portion
Data Source
AI summary
A coupling device for coupling a rod to a bone anchor includes a receiving part having first and second ends, a central axis, and two legs defining a recess at the first end for receiving the rod, a pressure member configured to exert pressure on an inserted head, and an actuating member with an engagement surface configured to engage the pressure member. When a first portion of the actuating member moves axially in a first direction, the engagement surface is configured to move from a first axial position to a second axial position to adjust the pressure member from a non-locking position where the head is pivotable to a locking position where the head is locked. When a second portion of the actuating member moves in the first direction, the pressure member is adjusted from the locking position back to the non-locking position.