External Fixation Strut With Telescopic Adjustment

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Solution Overview

Problem

Existing bone alignment devices require frequent changes of struts to accommodate varying distances between bones, leading to patient discomfort and increased clinical visits due to limitations in adjustable length ranges and the need for multiple measurement scales.

Innovation Solution

An external fixation strut with a main body, threaded rod, actuator, and movable arm, allowing for a large adjustable length range while maintaining a single measurement scale, enabling precise length adjustments without the need for strut changes, using a threaded rod mechanism that rotates to adjust the distance between fixed and movable arms.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If extended telescopic bodies are used to achieve large workable ranges, then the adjustable length range is improved, but the device complexity and measurement reliability deteriorate due to multiple measurement scales and reconfiguration needs

Engineering Contradiction:
Improveadjustable length rangeVSAvoidmultiple measurement scales
Core Design Contradiction:
Length of moving objectVSDevice complexity

Solution Approach 1:

The patent implements a dynamic adjustment mechanism where the inner rod can move telescopically within the outer rod, allowing the strut to adapt its length continuously. This dynamic structure enables a large adjustable range (e.g., 150mm to 450mm) while maintaining measurement accuracy through a single measurement scale on the outer rod, eliminating the need for multiple scales that would complicate the device.

Inventive Principle:
Principle #15Dynamics

Solution Approach 2:

The patent employs a nested structure where the inner rod is housed within the outer rod, creating a telescopic mechanism. This nesting allows compact storage when the strut is at minimum length and provides extended reach when the inner rod is pulled out to maximum length, achieving large workable ranges without requiring multiple separate components or measurement scales.

Inventive Principle:
Principle #7Nested doll (Nesting)

2Length of moving object

If multiple struts are changed to accommodate full workable range, then the adjustable length range is improved, but the loss of time and patient comfort deteriorate due to frequent clinic visits

Engineering Contradiction:
Improveworkable rangeVSAvoidclinic visit frequency
Core Design Contradiction:
Length of moving objectVSLoss of time

Solution Approach 1:

The patent designs the strut with a universal adjustment capability that covers the entire workable range required by treatment plans (from very small minimum distances to very large maximum distances between rings). This single strut performs multiple functions that would otherwise require different strut sizes, eliminating the need for frequent strut changes and clinic visits while maintaining the full adjustable range.

Inventive Principle:
Principle #6Universality (Multi-functionality)

3Length of moving object

If telescopic components are added to extend range, then the adjustable length range is improved, but the ease of operation deteriorates due to need for clinical visits to reconfigure

Engineering Contradiction:
Improveadjustable length rangeVSAvoidstrut reconfiguration
Core Design Contradiction:
Length of moving objectVSEase of operation

Solution Approach 1:

The patent incorporates a self-adjusting mechanism where the inner rod can be easily extended or retracted within the outer rod by the patient or clinician without requiring specialized tools or clinical visits. The threaded connection between the inner and outer rods allows for simple manual adjustment, enabling the strut to be reconfigured at the point of use and maintaining ease of operation while achieving extended range.

Inventive Principle:
Principle #25Self-service

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 solution provides a reliable and user-friendly method for bone alignment, reducing the need for frequent strut changes and clinical visits by offering a wide adjustable length range with a single measurement scale, enhancing treatment efficacy and patient comfort.

Implementation Method 1

The threaded rod may be non-threadably coupled to the fixed arm and threadably coupled to the movable arm so that rotation of the threaded rod moves the movable arm relative to the fixed arm.

Methodology Applied
Scientific EffectThreaded mechanism: Screw

Data Source

PatentEP4233749B1External fixation strut
Publication Date: 2024.08.07 SMITH & NEPHEW INC
  • EP4233749B1 patent drawingFigure 1
  • EP4233749B1 patent drawingFigure 2
  • EP4233749B1 patent drawingFigure 3

AI summary

An external fixation strut and corresponding systems and methods of use with a bone alignment device are disclosed. The external fixation strut may provide an enhanced range of adjustable lengths and may be connected to a bone alignment device, thereby enabling the bone alignment device to be used over a larger workable range. As a result, comfort of a patient may be improved as the need to switch out the external fixation strut may be prevented. The external fixation strut may also include a single measurement scale that may be easily viewed and used to adjust the length of the external fixation strut, thereby ensuring more accurate length adjustments.