Set Screw Antenna Layout for Wireless Spinal Load Sensing

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Solution Overview

Problem

Current load sensing assemblies for spinal implants face challenges in monitoring the connection force between longitudinal members and pedicle screws, as well as maintaining proper force distribution, which is crucial for effective spinal alignment and fusion.

Innovation Solution

A load sensing assembly is developed that includes a set screw with a central opening housing an integrated circuit and strain gauge, an antenna for communication, and a break-off head for secure engagement, allowing for real-time measurement and transmission of force data between the set screw and anchoring member, utilizing RFID or NFC technology for data storage and retrieval.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If an antenna is positioned within the central opening of the set screw, then the device complexity is reduced and manufacturing is simplified, but the antenna placement becomes more challenging due to spatial constraints

Engineering Contradiction:
Improvedevice complexityVSAvoidantenna placement
Core Design Contradiction:
Device complexityVSEase of manufacture

Solution Approach 1:

The patent positions the antenna within the central opening of the set screw, nesting the antenna inside the existing structural cavity. This eliminates the need for separate antenna housings or additional mounting components, thereby reducing device complexity while maintaining manufacturability through precise antenna placement during assembly

Inventive Principle:
Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent specifies that the antenna is positioned in the vertical direction above the adjustment head and within the central opening when viewed from the first end. This three-dimensional positioning strategy utilizes the vertical space within the central opening, allowing antenna integration without interfering with the horizontal threading or engagement features of the set screw

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Measurement precision

If the integrated circuit and strain gauge are positioned within the central opening of the set screw, then the measurement precision is improved, but the device complexity increases

Engineering Contradiction:
Improvemeasurement precisionVSAvoiddevice complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent combines the integrated circuit and strain gauge within the same central opening space, merging multiple functional components into a single integrated assembly. This consolidation improves measurement precision by ensuring proper alignment and connection between the strain gauge and integrated circuit, while the shared housing space actually reduces overall device complexity compared to separate mounting arrangements

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The central opening of the set screw serves multiple functions: it houses the antenna for wireless communication, contains the integrated circuit for data processing, and accommodates the strain gauge for force measurement. This multi-functional use of the central opening space eliminates the need for separate compartments or additional structural features, thereby improving measurement capabilities without proportionally increasing device complexity

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

This solution enables precise monitoring of forces during and after implantation, ensuring proper placement and torque of spinal implants, thereby enhancing the stability and effectiveness of spinal fusion procedures.

Implementation Method 1

a strain gauge in connection with the integrated circuit, wherein the integrated circuit and the strain gauge are positioned within the central opening of the set screw

Methodology Applied
Scientific EffectStrain gauge measurement: Piezoresistive Effect

Implementation Method 2

an antenna; an integrated circuit in communication with the antenna

Methodology Applied
Scientific EffectElectromagnetic radiation: Electromagnetic Induction

Data Source

PatentEP3823545B1Antenna placement for a digital set screw
Publication Date: 2024.04.10 WARSAW ORTHOPEDIC INC
  • EP3823545B1 patent drawingFigure 1
  • EP3823545B1 patent drawingFigure 2
  • EP3823545B1 patent drawingFigure 3

AI summary

A load sensing assembly for a spinal implant includes a set screw having a central opening that extends from a first end of the set screw toward a second end of the set screw. The second end of the set screw is configured to engage with an anchoring member. The load sensing assembly includes an antenna, an integrated circuit in communication with the antenna, where the integrated circuit is positioned within the central opening of the set screw, and a strain gauge in connection with the integrated circuit. The strain gauge is located within the central opening of the set screw in proximity to the second end of the set screw.