Removable Knee Prosthesis Sensors for Objective Activity Monitoring
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Solution Overview
Problem
Current patient-reported outcome measures (PROMs) for assessing knee replacement surgery are subjective, insensitive, and lack reliability and responsiveness, while wearable activity trackers are uncomfortable and impractical for long-term use, failing to provide accurate, objective data on medium to long-term activity profiles.
Innovation Solution
An implantable electronic device with a self-contained, removably mounted electromechanical motion sensor, such as a three-axis piezoelectric accelerometer, is integrated into a knee prosthesis, allowing for accurate measurement of acceleration and rotation, with wireless communication and a rechargeable battery, housed in a blind cavity accessible via minor surgery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If patient-reported outcome measures (PROMs) are used to assess knee replacement surgery, then patient experience and quality of life can be evaluated, but the measures are subjective, insensitive, and lack reliability and responsiveness
Solution Approach 1:
The patent replaces subjective patient-reported outcome measures with objective electromechanical sensing systems. Accelerometers and gyroscopes embedded in the knee prosthesis directly measure physical activity parameters, eliminating the subjectivity inherent in patient questionnaires and providing reliable, quantifiable data about actual movement patterns and activity levels
Solution Approach 2:
The patent introduces an intermediary wireless communication system that bridges the implantable sensor and external monitoring devices. This intermediary enables continuous data transmission from the prosthesis to external devices, allowing objective activity assessment without requiring direct patient input while maintaining system reliability through automated data collection
2Measurement precision
If wearable activity trackers are used for short-term activity assessment, then activity quantification is possible, but they are uncomfortable and impractical for long-term use
Solution Approach 1:
The patent embeds the electromechanical sensing system within the knee prosthesis structure itself. The accelerometers and gyroscopes are nested inside the implantable component, eliminating the need for external wearable devices. This integration provides continuous long-term monitoring without the discomfort of external trackers while maintaining precise activity measurement capabilities
Solution Approach 2:
The patent merges the activity monitoring function with the knee prosthesis structure. By combining the therapeutic function of the prosthesis with the diagnostic function of activity monitoring in a single integrated system, the patent eliminates the separate wearable device requirement and enables seamless long-term use without compromising patient comfort
3Loss of information
If implantable electronic device is integrated into knee prosthesis, then objective long-term activity data can be collected, but the device complexity and surgical implantation difficulty increase
Solution Approach 1:
The patent designs the implantable electronic device to serve multiple functions: structural support as part of the knee prosthesis, housing for electromechanical sensors, wireless communication transceiver, and power management system. This multi-functionality reduces the need for separate components and simplifies the overall device architecture while enabling comprehensive objective activity monitoring
Solution Approach 2:
The patent segments the implantable electronic device into modular functional components that can be independently manufactured and tested before final assembly. The device is divided into sensing modules, communication modules, and power modules, allowing for simplified manufacturing processes and easier surgical implantation while maintaining the capability for objective long-term activity data collection
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
Provides objective, long-term quantification of physical activity, enabling early detection of implant issues and promoting balanced activity levels, while maintaining the prosthesis's structural integrity and user comfort.
Implementation Method 1
an electromechanical motion sensor, such as a three-axis piezoelectric accelerometer
Data Source
AI summary
An implantable electronic device (12) and an endoprosthesis activity monitoring system (10) with a knee prosthesis (11) are developed. Knee prosthesis (11) has at least two blind cavities (35.1, 35.2), one in a lateral aspect of a femoral component (11.1) or tibial component (11.2), within which devices (12) are removably mounted and remote device (18) in wireless communication with devices (12) to receive data transmitted from it. Devices (12) are configured to track movement of the prosthesis (11) and to report same to the remote device (18). Devices (12) are self-contained and include an accelerometer (13), memory (15), a wireless communication module (14), processor (17) and a battery (16). Activity information analysed allows for early diagnosis of implant specific problems like loosening of the prosthesis. Location of devices (12) in the lateral aspects improves accessibility. Devices can be removed by minor surgery without compromising structural integrity of the knee prosthesis.