Expandable Pedicle Screw Core for Stronger Bone Press-Fit

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Solution Overview

Problem

Existing pedicle screw fixation systems face issues with screw loosening and pullout, particularly in patients with poor bone quality, leading to instability and potential failure of spinal fusion constructs.

Innovation Solution

The use of expandable pedicle implants, including expandable anchors and screws, which create a strong press-fit in the bone by expanding to fill the pedicle space, enhance bone-implant interface integrity, and facilitate osseointegration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional pedicle screws are used for fixation, then the procedure is simple and quick, but screw loosening and pullout occur especially in poor bone quality

Engineering Contradiction:

Improvescrew fixation stabilityVSAvoidimplant structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The pedicle screw incorporates an expandable proximal portion that can dynamically change volume from a compressed insertion state to an expanded fixation state. This dynamic expansion allows the screw to adapt to the pedicle space and create enhanced engagement with surrounding bone, improving fixation stability without requiring a completely complex implant design.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The expandable proximal portion is nested within the pedicle screw structure, with the expansion mechanism contained within the screw body. The proximal portion can be inserted in a compressed state through the pedicle channel and then expanded in situ, similar to nested dolls, allowing the implant to achieve its full functional form after insertion.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Strength

If expandable implants are used to improve bone-implant interface integrity, then primary stability and osseointegration improve, but the insertion procedure becomes more complex

Engineering Contradiction:

Improvebone-implant interface strengthVSAvoidinsertion procedure simplicity

Core Design Contradiction:

StrengthVSEase of operation

Solution Approach 1:

The expandable proximal portion is pre-configured within the pedicle screw before insertion, with the expansion mechanism prepared but not yet activated. The screw is inserted in a compressed state through a standard pedicle channel, and the expansion action is triggered after insertion, allowing preliminary positioning followed by strength enhancement.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The expansion mechanism is designed to be self-actuating or easily actuated through the existing screw structure. The proximal portion can expand using the screw's own structural elements or through simple manipulation of the screw body, reducing the need for additional complex insertion tools or procedures.

Inventive Principle:

Principle #25Self-service

3Strength

If the expandable proximal portion is used to fill unused pedicle space, then screw pullout strength increases, but the risk of cortical bone fracture increases

Engineering Contradiction:

Improvescrew pullout strengthVSAvoidcortical bone fracture risk

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The expansion action is localized to the proximal portion of the screw within the cancellous bone region of the pedicle, away from the cortical bone boundaries. The expandable sections are configured to expand radially outward into the available cancellous space without exerting excessive force on the surrounding cortical bone, thus improving pullout strength while minimizing fracture risk.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The expandable proximal portion changes its volume and radial dimensions after insertion, transitioning from a compressed insertion state to an expanded fixation state. This parameter change allows the screw to utilize unused pedicle space and engage more cancellous bone, increasing pullout strength while the controlled expansion process manages the risk to cortical bone.

Inventive Principle:

Principle #35Parameter changes

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 expandable implants improve primary stability, reduce micro-motion, and enhance osseointegration, thereby reducing the risk of screw loosening and construct failure, especially in osteoporotic bone.

Implementation Method 1

The expandable anchor has a collapsed configuration and an expanded configuration, thereby creating a press-fit in adjacent bone

Methodology Applied

Scientific EffectFriction: Friction

Implementation Method 2

The plurality of expandable sections may be configured to radially expand outward and away from one another, thereby increasing an outer diameter of the anchor

Methodology Applied

Scientific EffectMechanical interlocking: Mechanical Force

Implementation Method 3

The anchor may include a plurality of teeth arranged in an array about the periphery of the expandable sections. The teeth may be pyramidal in shape or otherwise configured to engage bone

Methodology Applied

Scientific EffectCompression: Compression

Data Source

PatentUS12551241B2Expandable bone core for pedicle screw fixation

Publication Date: 2026.02.17 GLOBUS MEDICAL INC

AI summary

Pedicle bone anchor implants, assemblies, and methods thereof. The implant may include an expandable anchor having a body with expandable sections separated by one or more expansion joints, a plurality of expandable teeth, or an expandable head. The expandable anchor has a collapsed configuration and an expanded configuration, thereby creating a press-fit in adjacent bone.