Constant-Force Spring Orthopedic Traction System

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Solution Overview

Problem

Current traction devices for limb surgery lack the ability to maintain a constant tractive force during procedures due to gradual stretching or slippage, requiring frequent adjustments and prolonging surgery, and existing constant-force springs are not adjustable enough for surgical applications.

Innovation Solution

A system utilizing constant-force springs with a base tractive force and supplementary springs that can be reversibly changed between coupled and uncoupled configurations to provide discrete adjustments in traction force without repositioning the limb, allowing for continuous application of a predetermined set of constant tractive forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If continuously adjustable traction is used, then the surgeon can select and readjust the desired tractive force, but the device cannot maintain a constant tractive force during the procedure requiring repeated adjustments

Engineering Contradiction:

Improveadjustability of tractive forceVSAvoidconstancy of tractive force

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The traction device divides the continuous adjustment range into discrete force levels, each maintained by a separate constant-force spring. This segmentation allows the system to offer multiple predetermined force options while maintaining constant force within each level, resolving the contradiction between adjustability and force constancy.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The device incorporates a dynamic switching mechanism that allows rapid transition between discrete force levels. The quick-release carabiner and movable carriage assembly enable the surgeon to dynamically adjust between predetermined force levels without complex procedures, maintaining both adaptability and force stability.

Inventive Principle:

Principle #15Dynamics

2Ease of operation

If the limb is allowed to move with respect to the traction device, then the limb can be repositioned during surgery, but the tractive force increases or decreases with distinct positions requiring readjustment

Engineering Contradiction:

Improvelimb repositioning capabilityVSAvoidstability of tractive force

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The constant-force springs automatically compensate for limb movement and position changes. As the limb moves or the carriage repositions, the spring mechanism self-adjusts to maintain the predetermined constant force without requiring surgical intervention, thus maintaining force stability while allowing operational flexibility.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The device changes the physical state of the spring system from fixed-length to variable-length constant-force mechanism. This parameter change allows the spring to extend and retract while maintaining constant force, enabling limb repositioning without force fluctuation.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If repeated adjustments are made to maintain constant tractive force, then the force stability is improved, but the surgery time increases and cost increases

Engineering Contradiction:

Improveconstancy of tractive forceVSAvoidsurgery duration

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The constant-force springs are pre-configured to deliver predetermined force levels. This preliminary preparation eliminates the need for repeated adjustments during surgery, as the force constancy is built into the spring mechanism itself rather than requiring active management.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The constant-force spring mechanism provides inherent feedback through its mechanical design. As the spring extends or contracts, the force remains constant by design, automatically compensating for any position changes without requiring external monitoring or adjustment.

Inventive Principle:

Principle #23Feedback

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

Enables quick, easy, and reproducible application of consistent tractive forces, maintaining stability as the limb pivots, stretches, or slips, reducing the need for repeated adjustments and improving surgical efficiency.

Implementation Method 1

constant-force springs may include one or more main springs that apply a base tractive force and at least one supplementary spring that can apply a supplementary tractive force

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS7857780B2Discretely adjustable orthopedic traction using constant-force springs

Publication Date: 2010.12.28 ACUMED

AI summary

System, including method and apparatus, for applying traction to a patient's limb using constant-force springs. The constant-force springs may include one or more main springs that apply a base tractive force and at least one supplementary spring that can apply a supplementary tractive force to the limb. The at least one supplementary spring may be changeable reversibly between uncoupled and coupled configurations while the base tractive force is applied continuously to the limb and without repositioning the limb, thereby providing discrete adjustment of traction force while the limb remains in traction.