Multi-Axis Force Sensor for Knee Joint Load Balancing
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Solution Overview
Problem
Current methods for measuring joint loads, particularly in knee arthroplasty procedures, are inadequate in accurately assessing normal and shear forces, leading to issues like improper load balancing, stiffness, instability, and high rates of revision surgeries due to uneven wear and early failure of knee joint replacements.
Innovation Solution
A device that measures contact forces and center of pressure across the knee joint, using a system with multiple force sensors and a machine learning system to provide comprehensive load measurements, including medial-lateral, compression-distraction, and anterior-posterior forces, adaptable for both total and unicompartmental knee arthroplasty, and capable of active and passive loading conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple force sensors are used to measure joint loads accurately, then measurement precision improves, but device complexity increases
Solution Approach 1:
The device divides the measurement function into multiple independent force sensors, each measuring specific components of joint load (normal force, shear forces in different directions). This segmentation allows accurate multi-axis measurement while keeping each sensor module simple and manageable.
Solution Approach 2:
The force sensor system is designed to measure multiple types of loads simultaneously (compression, tension, shear forces in multiple directions) using a integrated sensor array. This multi-functionality reduces the need for separate measurement devices for different load types.
2Measurement precision
If a comprehensive multi-axis force sensor system is implemented, then load balancing accuracy improves, but ease of operation deteriorates
Solution Approach 1:
The system provides real-time feedback of multi-axis force measurements to the surgeon during the procedure. This feedback mechanism guides load balancing adjustments by displaying measured forces and suggesting corrective actions, making the complex measurement process easier to operate and interpret.
Solution Approach 2:
The patent introduces an intermediary processing system that converts complex multi-axis sensor data into interpretable load balancing metrics and guidance for the surgeon. This intermediary layer simplifies the interface between the complex sensor system and the user.
3Reliability
If force sensors are embedded in the joint replacement device, then reliability of load measurement improves, but manufacturing precision requirements increase
Solution Approach 1:
The force sensors are merged with the structural components of the joint replacement device (femoral component, tibial component). This integration ensures reliable load measurement while using the existing structural geometry to support the sensors, reducing the need for separate precision mounting features.
Solution Approach 2:
The patent employs strain gauge sensors that convert mechanical strain into electrical signals. By changing the measurement parameter from direct force measurement to strain measurement, the system achieves reliable load data while being more tolerant of manufacturing variations in sensor placement.
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 load balancing during knee arthroplasty, improving patient outcomes by reducing revision rates and ensuring even wear on knee joint replacements, as it provides real-time data for intraoperative adjustments and postoperative monitoring.
Implementation Method 1
a first force sensor detecting a load input on the knee joint along a first axis and producing a first output voltage indicating at least one of normal and shear force on the knee joint
Implementation Method 2
a second force sensor detecting the load input on the knee joint along a second axis displaced from the first axis and producing a second output voltage indicating the at least one of normal and shear force on the knee joint
Implementation Method 3
a third force sensor detecting the load input on the knee joint along a third axis displaced from the first and second axis and producing a third output voltage indicating the at least one of normal and shear force on the knee joint
Data Source
AI summary
A device for measuring normal force, shear forces, and location of the center of pressure in a joint, for example, in lateral and/or medial knee compartments, in the preclinical environment and in the surgical environment to balance the contact forces over a full flexion range. Further, in certain embodiments, the device measures active, passive and shear forces over a full flexion range and is adaptable for both total knee arthroplasty and unicompartmental knee arthroplasty.