Threaded Implants with Counter-Rotating Supports for Sacroiliac Fusion

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Solution Overview

Problem

Current surgical methods for sacroiliac joint fusion, such as using screws and plates, require large incisions and deep tissue dissection, causing trauma and are susceptible to implant rotation and loosening, especially in joints subjected to torsional forces, leading to potential implant failure.

Innovation Solution

The development of threaded implants with external threads and internal counter-rotating support structures, featuring fenestrations filled with porous infill to promote bone growth, and designs that resist rotation, such as triangular cross-sections and multiple thread starts, allowing for minimally invasive insertion and stable fixation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional screws and plates are used for sacroiliac joint fusion, then the joint can be fixed, but the surgery requires large incisions and deep soft tissue dissection causing trauma

Engineering Contradiction:

Improvejoint fixationVSAvoidtissue trauma

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The implant is divided into distinct functional segments: external threads for bone engagement, internal counter-rotating support structure for anti-rotation, and fenestrations for bone ingrowth. This segmentation allows each component to address specific requirements while minimizing overall surgical trauma.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The fenestrations in the implant body are designed to promote bone ingrowth through the implant structure, creating a biological fixation mechanism that reduces reliance on large-scale surgical exposure and extensive soft tissue dissection.

Inventive Principle:

Principle #31Porous materials

2Reliability

If traditional screws are used, then the joint can be fixed, but the implants are susceptible to rotation and loosening under torsional forces

Engineering Contradiction:

Improvejoint fixationVSAvoidimplant rotation resistance

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The internal support structure features a non-circular cross-section (triangular, rectangular, or oval) that prevents rotation of the implant within the bone. This asymmetric geometry ensures that the implant cannot rotate under torsional loads, addressing the instability issue of traditional circular screws.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The internal counter-rotating support structure is specifically designed to counteract rotational forces applied to the external threads. When torsional forces attempt to rotate the implant, the asymmetric internal structure engages with the bone to provide an equal and opposite resistance, preventing loosening.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

3Reliability

If threaded implants are used to promote bone fusion, then bone growth can be enhanced, but the implant structure becomes more complex

Engineering Contradiction:

Improvebone fusionVSAvoidimplant structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Multiple functions are merged into a single implant body: external threads for initial bone engagement and fixation, internal counter-rotating support structure for anti-rotation stability, and fenestrations for long-term biological fixation through bone ingrowth. This integration achieves comprehensive fixation without requiring multiple separate components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The implant serves multiple functions simultaneously: mechanical fixation through threading, rotational stabilization through asymmetric geometry, and biological integration through porous fenestrations. This multi-functionality reduces the need for additional fixation instruments and bone grafting procedures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

These implants provide immediate post-op stability, minimize rotation, and enhance bone fusion by promoting bony ingrowth and ongrowth, reducing the need for autologous bone grafts and other fixation instruments, while maintaining structural integrity and weight-bearing capacity.

Implementation Method 1

fenestrations filled with porous infill to promote bone growth

Methodology Applied

Scientific EffectBone ingrowth:

Implementation Method 2

fenestrations filled with porous infill to promote bone growth

Methodology Applied

Scientific EffectBone ongrowth:

Implementation Method 3

external threads configured to thread into bone

Methodology Applied

Scientific EffectThreading: Screw

Implementation Method 4

internal support structure has a helical arrangement that extends in an opposite direction to the external threads

Methodology Applied

Scientific EffectCounter-rotation resistance:

Data Source

PatentUS12427028B2Threaded implants and methods of use across bone segments

Publication Date: 2025.09.30 SI BONE INC

AI summary

A threaded implant can be provided with an elongated main body having external threads configured to thread into bone, and an internal support structure located within the external threads. The internal support structure has a helical arrangement that extends in an opposite direction to the external threads. Other threaded implants and methods are also disclosed.