Modular Pedicle Screw Cam Lock Mechanism

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Solution Overview

Problem

Existing fixed angle pedicle screw assemblies for spine rod applications lack a robust and easy-to-use locking mechanism for securing the pedicle screw to the spine rod holder at a fixed angle, which is essential for surgical precision and stability.

Innovation Solution

A modular pedicle screw assembly featuring a head with radially disposed closures that rotate to selectively capture and release a spherical end of a threaded shank, utilizing a cam action mechanism to securely lock the shank in place, allowing for easy assembly and disassembly through a tulip-shaped body with a circumferential configuration that changes diameter upon rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a robust locking mechanism is provided to secure the pedicle screw to the spine rod holder, then the reliability of the connection is improved, but the device complexity increases

Engineering Contradiction:

Improveconnection reliabilityVSAvoidlocking mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The locking mechanism is divided into multiple independent closures (typically three) that can be individually actuated. Each closure independently engages with the spherical end of the shank, providing redundant securing while maintaining simplicity through modular repetition of the same basic locking element.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The closures are designed to be movable rather than fixed, allowing them to rotate between an open position (where they do not engage the shank) and a closed position (where they engage and lock the shank). This dynamic capability enables easy assembly and disassembly while ensuring secure locking when engaged.

Inventive Principle:

Principle #15Dynamics

2Stability of the object's composition

If a secure locking mechanism is provided to fix the pedicle screw at the desired angle, then the stability of the fixed angle is improved, but the ease of operation for assembly and disassembly deteriorates

Engineering Contradiction:

Improvefixed angle stabilityVSAvoidassembly and disassembly ease

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The traditional complex threaded or keyed locking mechanisms are replaced with a simpler cam-based system. The cam surface on each closure provides mechanical advantage, allowing a small rotational motion to generate a large locking force that secures the fixed angle stability without requiring complex assembly procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If a modular design with multiple components is used, then the adaptability and ease of assembly are improved, but the device complexity increases

Engineering Contradiction:

Improvemodular assembly adaptabilityVSAvoidnumber of components

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The closures serve multiple functions: they act as locking elements, positioning elements, and engagement elements all in one component. Each closure is identical and can be used in any position around the spherical end, providing universality that reduces the need for specialized components for different functions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The locking mechanism merges the functions of multiple traditional components (lock nuts, set screws, and positioning elements) into a single integrated closure component. This consolidation reduces the total number of parts while maintaining the necessary adaptability and locking capability.

Inventive Principle:

Principle #5Merging (Combining)

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 modular design provides a secure and reversible locking mechanism, ensuring the pedicle screw remains fixed at the desired angle, facilitating precise surgical procedures and reducing the complexity of assembly and disassembly processes.

Implementation Method 1

The cam structure selectively engages with the closures through rotation relative to the internal chamber to increase and decrease size of the opening formed by the closures to capture and release the spherical end of the threaded shank

Methodology Applied

Scientific EffectCam action: Cam

Data Source

PatentUS10973553B2Modular pedicle screw with multi-part cam lock structure

Publication Date: 2021.04.13 LIFE SPINE INC

AI summary

A modular pedicle screw assembly has a multi-part cam lock structure for fixing a threaded shank to a head subassembly. A modular pedicle screw assembly provides capture and release of a spherical end of a threaded shank by a head through rotation of closures radially disposed in an internal chamber of the head. Geometry of the closures cooperate with geometry of the internal chamber, providing a selective cam action between the closures and the internal chamber to increase and decrease size of an opening formed by the closures. Closure rotation produces an open state where the spherical end of the threaded shank can pass through the closures, releasing the spherical end of the threaded shank from the head, and a closed state where the spherical end of the threaded shank cannot pass through the closures thereby capturing the spherical end of the threaded shank in the head.