Knee Joint Balancing With Ligament-Specific Tension Measurement
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Solution Overview
Problem
Existing methods for identifying ligament tension in knee joint balancing during total knee arthroplasty are inaccurate due to the inability to individually isolate and measure the tension of the medial and lateral collateral ligaments, leading to improper soft tissue tensioning and instability.
Innovation Solution
A system and method using sensors and an inertial measurement unit to measure load and deflection angles, determining stress-strain curves for both medial and lateral collateral ligaments, allowing for precise identification of target ligament tension.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If joint distraction device with force sensors is used to measure soft tissue tension, then measurement capability is provided, but inability to individually isolate and tension MCL or LCL during distraction occurs
Solution Approach 1:
The sensor assembly is divided into separate medial and lateral load cells that independently measure forces on each side of the joint. This segmentation allows individual measurement of MCL and LCL tensions without requiring manual isolation, as each sensor independently captures ligament-specific forces during distraction
Solution Approach 2:
The sensor assembly acts as an intermediary device placed within the joint space that automatically measures and differentiates forces on medial and lateral sides. This intermediary system eliminates the need for surgeon skill in manually isolating ligaments, as the sensors automatically capture individual ligament tensions through their respective measurement positions
2Loss of information
If manual force application and subjective observation is used to evaluate ligament stress-strain properties, then patient-specific properties can be identified, but accuracy is dependent on surgeon skill
Solution Approach 1:
The sensor assembly performs self-service by automatically measuring forces and calculating stress-strain curves without requiring surgeon intervention for force application or observation. The system independently captures ligament properties through automated sensing and computation, eliminating surgeon skill dependency while preserving patient-specific information
Solution Approach 2:
Manual mechanical assessment by the surgeon is replaced with an automated sensor system that uses force sensors and computational algorithms to evaluate ligament stress-strain properties. This substitution maintains patient-specific property identification while significantly improving measurement precision through objective, quantifiable data
3Measurement precision
If joint distraction is applied to measure soft tissue tension, then tension measurement is enabled, but tension in opposite ligament is invariably caused
Solution Approach 1:
The measurement system is segmented into independent medial and lateral force sensors that separately measure forces on each side of the joint. This segmentation allows the system to distinguish and measure individual ligament tensions even when both sides are subjected to distraction forces, eliminating cross-ligament interference by independently capturing each ligament's specific tension
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 accurate, patient-specific ligament tensioning, reducing implant instability and improving knee joint balance by quantifying and isolating the tension of individual ligaments.
Implementation Method 1
The sensors may include an inertial measurement unit to measure the first deflection angles
Implementation Method 2
measuring first load values at a first condyle using a first sensor during the rotation step
Implementation Method 3
determining a stress-strain curve of a first ligament adjacent the second condyle from the first load values and first deflection angles
Data Source
AI summary
Disclosed herein are a system for determining ligament tension and a method for utilizing the same in a knee balancing procedure. The system according may include a first sensor to measure a first load at a first condyle of a femur, a second sensor to measure a second load at a second condyle of the femur, an inertial measurement unit to measure angular change of a tibial mechanical axis of a tibia during a rotation of the tibia in a coronal plane, and a display in communication with the first sensor, the second sensor and the inertial measurement unit for displaying a ligament stress-strain curve. The method may include the steps of rotating a tibia toward a first condyle, measuring first load values and first deflection angles of the tibia, and determining a stress-strain curve of a first ligament from the first load values and first deflection angles.