Robot-Aided Soft Tissue Balancing for Quantitative Knee Arthroplasty

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Solution Overview

Problem

Conventional methods for soft tissue balancing in orthopedic surgery lack precision and accuracy, leading to potential joint instability due to qualitative assessments of patient range of motion.

Innovation Solution

A robot-aided knee arthroplasty system utilizing a robotic arm with sensors and a CAS controller for precise soft tissue balancing, including tools like laminar spreaders and force-torque sensors to measure tension and rotation, enabling quantitative assessment and adjustment of implant sizes and locations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional hand-based soft tissue evaluation is used, then the surgical procedure is simple and quick, but the measurement precision and accuracy are poor leading to potential joint instability

Engineering Contradiction:
Improvesoft tissue balancing precisionVSAvoidsurgical system complexity
Core Design Contradiction:
Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the conventional manual hand-based soft tissue evaluation with a robotic arm system that uses force-torque sensors to apply and measure forces on the bone. This substitution of mechanical evaluation with sensor-based measurement achieves quantitative data collection, significantly improving measurement precision while automating the soft tissue balancing assessment process

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a robotic arm as an intermediary device between the surgeon and the patient's joint. The robotic arm equipped with force-torque sensors acts as a mediator to apply controlled forces and measure soft tissue tension, providing objective quantitative data that bridges the gap between manual evaluation and precise measurement

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If qualitative assessment of range of motion is used, then the evaluation process is simple, but the reliability of joint stability assessment is poor

Engineering Contradiction:
Improvejoint stability assessment reliabilityVSAvoidsoft tissue tension measurement difficulty
Core Design Contradiction:
ReliabilityVSDifficulty of detecting and measuring

Solution Approach 1:

The patent replaces subjective qualitative range of motion assessment with objective sensor-based measurement. Force-torque sensors mounted on the robotic arm directly measure soft tissue tension forces, converting an unreliable qualitative assessment into reliable quantitative data that objectively reflects joint stability

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements real-time feedback through force-torque sensors that continuously measure soft tissue tension during the evaluation process. This feedback mechanism allows the system to adjust and refine measurements, providing reliable data on joint stability and enabling informed surgical decisions based on objective feedback rather than subjective assessment

Inventive Principle:
Principle #23Feedback

3Manufacturing precision

If manual soft tissue evaluation is used, then the surgical time is short, but the productivity and accuracy of implant positioning are reduced

Engineering Contradiction:
Improveimplant positioning precisionVSAvoidsurgical procedure efficiency
Core Design Contradiction:
Manufacturing precisionVSProductivity

Solution Approach 1:

The robotic arm system performs self-measurement of soft tissue balancing by automatically applying forces and recording sensor data without requiring extensive manual intervention. This self-service capability allows the system to gather precise measurement data efficiently, improving implant positioning precision while maintaining surgical productivity through automation

Inventive Principle:
Principle #25Self-service

Solution Approach 2:

The patent replaces manual measurement techniques with an automated robotic system that uses force-torque sensors to evaluate soft tissue balancing. This substitution provides precise quantitative data for implant positioning while streamlining the evaluation process, thereby improving both positioning precision and surgical efficiency through automation

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

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

Enhances the precision and accuracy of soft tissue balancing, reducing the risk of joint instability by providing real-time data and automated adjustments during surgical procedures.

Implementation Method 1

A robot-aided knee arthroplasty system utilizes a robotic arm with sensors and a CAS controller for precise soft tissue balancing, including tools like laminar spreaders and force-torque sensors to measure tension and rotation

Methodology Applied
Scientific EffectForce measurement: Force

Implementation Method 2

A robot-aided knee arthroplasty system utilizing a robotic arm with sensors and a CAS controller for precise soft tissue balancing, including tools like laminar spreaders and force-torque sensors to measure tension and rotation

Methodology Applied
Scientific EffectMechanical force application: Mechanical Force

Data Source

PatentEP3471649B1Soft tissue balancing in articular surgery
Publication Date: 2025.07.16 ZIMMER INC
  • EP3471649B1 patent drawingFigure 1
  • EP3471649B1 patent drawingFigure 2
  • EP3471649B1 patent drawingFigure 3

AI summary

Systems and methods may be used to perform robot-aided surgery. A system may include a robotic controller to monitor a position and orientation of an end effector coupled to an end of a robotic arm. The robotic controller may apply a force to a bone using the end effector, such as via a soft tissue balancing component. The robotic controller may determine soft tissue balance using information from a tracking system, such as a position of a first tracker affixed to the bone. The soft tissue balance may be output, such as to a display device.