Spinal Interbody Fusion Device Dual Locking Mechanism

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Solution Overview

Problem

Existing spinal fusion devices lack mechanisms to prevent anchor member backout, facilitate removal, guide insertion, and provide stability, leading to issues such as screw loosening, overtightening, and lack of control during surgery.

Innovation Solution

The implementation of a dual locking mechanism in the implant assembly, which includes a first locking mechanism to prevent backout and a second locking mechanism that acts as a centering aid during insertion, provides mechanical advantage for screw placement and removal, and enhances stability by engaging a substantial portion of the anchor member, reducing the need for separate guides and preventing overtightening.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single locking mechanism is used to prevent anchor member backout, then the device structure is simple, but the device lacks the ability to facilitate removal and guide insertion

Engineering Contradiction:

Improveprevention of anchor member backoutVSAvoiddevice structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The locking mechanism is divided into two distinct sections: a first locking section with deformable locking elements that engage the anchor member hub, and a second locking section with threaded engagement that secures the anchor member shank. This segmentation allows each section to perform its specific function (preventing backout vs. facilitating removal) while maintaining overall device integrity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The dual locking mechanism serves multiple functions: the first locking section prevents backout during normal operation, the second locking section facilitates removal when needed, and the threaded portion also acts as a guide during insertion. This multi-functionality resolves the contradiction by integrating several capabilities into a unified structure.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If deformable locking rings are used to inhibit bone screws from backing out, then the locking mechanism is simple, but the screw passages are relatively short and engage only a small portion of the screw heads

Engineering Contradiction:

Improveinhibition of screw backoutVSAvoidscrew passage length

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution transitions from a single-dimensional deformable ring approach to a two-dimensional dual-section locking system that engages the anchor member at multiple locations along its length, providing comprehensive securing without requiring excessive passage length.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Reliability

If bone screws are rotated to separate the orientation of the external thread from the internal thread runout, then the screw is prevented from backing out, but there is no mechanism to assist removal of the bone screw

Engineering Contradiction:

Improveprevention of screw backoutVSAvoidscrew removal

Core Design Contradiction:

ReliabilityVSEase of repair

Solution Approach 1:

The locking elements are designed to be deformable, allowing them to flex during insertion and locking, but remain rigid during normal operation to prevent backout. This dynamic behavior enables the same structure to facilitate both secure locking and controlled removal when needed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The deformable locking elements can be temporarily deformed during insertion to allow screw passage, then recover their original shape to lock the screw in place. During removal, the process is reversed, allowing the screw to be extracted without permanent damage to the locking mechanism.

Inventive Principle:

Principle #34Discarding and recovering

4Device complexity

If the spacer provides no control against overtightening of bone screws, then the device structure is simple, but the delicate thread in the bone will be damaged and stripped

Engineering Contradiction:

Improvedevice structureVSAvoidbone thread integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The deformable locking elements provide tactile and visual feedback during screw insertion, allowing the surgeon to sense when the screw is properly seated and locked. This feedback mechanism prevents overtightening by signaling the appropriate stopping point without requiring complex additional structures.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8377139B2Standalone interbody fusion device with locking and release mechanism

Publication Date: 2013.02.19 AESCULAP IMPLANT SYSTEMS LLC

AI summary

An implantable assembly includes an anchor member and a spacer. The anchor member has a hub portion and a shank portion. The spacer includes a central opening to receive bone fusion material and at least one passage for receiving the anchor member. In one embodiment, the passage includes first and second means for locking the anchor member in the passage against backout. The second means for locking the anchor member in the passage against backout includes means for centering the anchor member in the passage and means for stabilizing the anchor member in the passage. In addition, the second means for locking the anchor member in the passage against backout provides a mechanical advantage to assist in driving the screw into bone and mechanical advantage to assist in reversing the screw out of the spacer.