Modular Ligament Strain Sensor for TKA
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Solution Overview
Problem
Current methods for measuring ligament strain during total knee arthroplasty (TKA) surgery are complex, often require cutting ligament fibers, and lack modularity, leading to instability and increased wear of prosthetic devices, necessitating repeat surgeries.
Innovation Solution
A device comprising ligament-retaining elements, a bridging element, and a sensor that measures strain differences without cutting ligaments, allowing for remote measurement and minimizing interference with the ligament, using a wire with low deformation materials and a linear variable differential transformer sensor for accurate strain detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ligament strain measurement methods are used during TKA surgery, then ligament tension can be assessed, but the measurement process is complex, requires cutting ligament fibers, and lacks modularity
Solution Approach 1:
The measurement device is divided into modular components: a sensor unit with housing, a separate ligament-retaining element, and a bridging element. This segmentation allows each component to be optimized independently and facilitates sterile processing and surgical installation while maintaining measurement accuracy.
Solution Approach 2:
A bridging element is introduced as an intermediary component that connects the sensor to the ligament without requiring direct attachment to bone or cutting of ligament fibers. The bridging element transmits ligament strain to the sensor while maintaining a minimally invasive configuration.
2Measurement precision
If ligament fibers are cut to measure strain, then measurement can be performed, but ligament strength is reduced and instability occurs
Solution Approach 1:
The ligament-retaining element applies localized compression to a small portion of the ligament without cutting or damaging the surrounding tissue. This localized interaction allows strain measurement while preserving the overall integrity and strength of the ligament.
Solution Approach 2:
The ligament itself serves as the structural element being measured without requiring external modification. The device measures strain through the ligament's natural mechanical properties without altering its continuity or strength.
3Measurement precision
If complex measurement procedures are used, then ligament strain can be measured, but surgery time increases and productivity decreases
Solution Approach 1:
The sensor unit is pre-assembled and sterilized before surgery, with the ligament-retaining element and bridging element prepared in advance. This preliminary preparation eliminates time-consuming assembly steps during surgery and allows for quick installation and measurement.
4Measurement precision
If non-modular measurement devices are used, then measurement can be performed, but adaptability to different surgical needs is reduced
Solution Approach 1:
The device is designed as a modular system with separate sensor unit, ligament-retaining element, and bridging element that can be independently selected and combined. This segmentation enables adaptation to different ligament sizes, surgical approaches, and measurement requirements.
Solution Approach 2:
The sensor unit can measure strain in different ligaments (collateral ligaments, cruciate ligaments) by simply changing the ligament-retaining element and bridging element configuration. This universal design allows a single device platform to serve multiple surgical measurement needs.
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 enhances functional performance, reduces abnormal motion, and provides a more natural postoperative feeling by accurately measuring ligament strain, enabling better implant sizing and positioning, thus reducing the need for repeat surgeries and improving long-term prosthesis durability.
Implementation Method 1
a sensor configured to measure a strain-indicating parameter representing a position of the wire relative to the proximal end of the bridging element
Data Source
AI summary
The current invention relates to an integrated device suitable for measuring the difference between a strain in a ligament at a first point in time and said strain at a second point in time, said integrated device comprising: a ligament-attaching element adapted to be fastened on said ligament; a slider module adapted to be fastened on said ligament near said first ligament-attaching element, said slider module comprising a slider guiding channel; a slider comprising a distal slider end and a proximal slider end, said distal slider end fastened on said ligament-attaching element, said proximal slider end guided in said slider guiding channel; a sensor configured to measure a strain-indicating parameter representing a position of said proximal slider end for obtaining said difference between said strain in said ligament at said first point in time and said strain at said second point in time, wherein said sensor comprises a Hall sensor which converts a position of said proximal slider end into a conditioned electrical signal carrying said measurement of said strain-indicating parameter.