Strain-Gauged Joint Tensioning for Pre-Resection Knee Laxity
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Solution Overview
Problem
The lack of standardization in collecting soft-tissue tension/laxity data during robotically assisted total knee arthroplasty leads to inconsistent results, and existing methods require tibial resection before ligament tensioning, complicating the quantification of varus/valgus force application.
Innovation Solution
A joint tensioning system with a first and second arm configured to align with joint locations, allowing manual separation to apply a distraction force, equipped with a sensor device to measure strain and determine the applied distraction force, and a computing device to calculate the force based on the strain measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If manual stress application is used to quantify ligament laxity, then the procedure can be performed without tibial resection, but the amount of varus/valgus force applied cannot be standardized
Solution Approach 1:
The patent replaces manual mechanical stress application with an instrumented system that uses sensors (strain gauges, force sensors) to objectively measure and quantify the distraction force applied to the knee joint. This substitution transforms subjective manual force application into precise, measurable mechanical data, resolving the contradiction between procedural simplicity and measurement accuracy.
2Extent of automation
If z-retractor is used to apply varus/valgus stress, then automated force application is achieved, but standardization of force magnitude remains challenging
Solution Approach 1:
The patent implements a feedback system where sensors continuously measure the distraction force applied to the joint, and this data is transmitted to a computing device that provides real-time feedback to the operator. The system can indicate when a target force magnitude is reached, enabling standardized force application while maintaining automation. This feedback loop resolves the contradiction by providing both automated force application and precise force standardization.
3Reliability
If tibial resection is performed before ligament tensioning, then soft-tissue assessment can be conducted, but the procedure becomes more complex and time-consuming
Solution Approach 1:
The patent enables soft-tissue tension assessment to be performed before tibial resection by using the instrumented distraction device to apply controlled forces and measure ligament laxity in the intact joint. This preliminary assessment allows surgeons to evaluate soft-tissue balance prior to bone resection, potentially guiding resection planning and reducing the need for intraoperative ligament releases, thereby simplifying the overall procedure while maintaining assessment reliability.
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
Standardizes the collection of soft-tissue tension/laxity data, enabling precise quantification of ligament laxity without requiring tibial resection, thereby improving the consistency and accuracy of robotic knee arthroplasty procedures.
Implementation Method 1
A sensor device is located in the first arm and positioned to measure a strain applied to the first tip based on the distraction force applied to the joint
Data Source
AI summary
A joint tensioning device and methods of use thereof are disclosed. The joint tensioning device includes a flexing arm and a loading arm having a tensioning tip and a loading tip, respectively, configured for insertion into a joint. The flexing arm is coupled to the loading arm such that, during use, the loading arm may be adjusted to separate the tensioning tip and the loading tip to apply a distraction force to the joint. A strain gauge measures strain applied to the flexing arm based on the applied distraction force. The measured strain is used to determine the amount of force applied to the joint. The force data is employed in surgical planning to determine the amount of joint laxity when a particular load is applied to the joint.