Instrumented Knee Gap Balancing With Ligament Force Modeling
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Solution Overview
Problem
Current state-of-the-art gap balancing devices for total knee arthroplasty are complex, difficult to use, and do not enable proper balance with the patella in place, particularly when working with different knee implant systems.
Innovation Solution
An instrumented tensioner-balancer is used to measure bone and soft tissue parameters of the knee joint by applying a distraction force, collecting data, and deriving a digital geometric model to optimize ligament tautness, allowing for precise gap balancing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current state-of-the-art gap balancing devices are used, then gap balancing can be performed, but the devices are complex and difficult to use
Solution Approach 1:
The gap balancing device is divided into separate functional modules: a tensioning device for applying distraction force, a measurement device for measuring gap distances, and a calculation device for determining ligament tension. This segmentation allows each module to be optimized independently and simplifies the overall system architecture, making the device easier to use while maintaining gap balancing capability.
Solution Approach 2:
The gap balancing device is designed to be system-independent, meaning it can be used with different knee implant systems rather than being proprietary to one manufacturer. This multi-functionality is achieved by using universal measurement and calculation methods that work across various implant types, reducing the need for multiple specialized devices and simplifying the surgical workflow.
2Reliability
If current gap balancing devices are used, then gap balancing can be performed, but they do not enable proper balance with the patella in place
Solution Approach 1:
The gap balancing device is designed to be system-independent, meaning it can be used with different knee implant systems rather than being proprietary to one manufacturer. This multi-functionality is achieved by using universal measurement and calculation methods that work across various implant types, reducing the need for multiple specialized devices and simplifying the surgical workflow.
Solution Approach 2:
The device allows for dynamic adjustment of measurement parameters and distraction forces to accommodate different implant systems and patient anatomies. By changing parameters such as distraction force magnitude, measurement reference points, and calculation algorithms, the device adapts to various surgical scenarios including those with the patella in place, enhancing its versatility without compromising reliability.
3Productivity
If manual gap balancing methods are used, then surgical procedure can be completed, but achieving proper balance is difficult and complex
Solution Approach 1:
The gap balancing device incorporates real-time feedback through automated measurement and calculation functions. The measurement device continuously monitors gap distances, and the calculation device immediately computes ligament tension values, providing the surgeon with real-time feedback on balancing status. This eliminates the need for complex manual assessments and makes achieving proper balance straightforward and efficient.
Solution Approach 2:
Traditional manual gap balancing methods relying on surgeon experience and physical manipulation are replaced with an instrumented system that uses sensors, measurement devices, and calculation algorithms. This substitution of mechanical/manual processes with automated measurement and computation systems significantly improves ease of operation while maintaining surgical efficiency.
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 precise balancing of flexion and extension gaps in knee arthroplasty by providing a digital geometric model for selecting the optimal ligament tautness, facilitating the use of different knee implant systems.
Implementation Method 1
a means of applying a distraction force to the knee joint
Implementation Method 2
collecting distraction height data and distraction force data of the femur bone relative to the tibia bone from at least one sensor
Data Source
AI summary
A method of evaluating a human knee joint includes: inserting a tensioner-balancer; moving the knee joint to one or more positions within its range of motion; using the tensioner-balancer to maintain a predetermined distraction load range or a predetermined distraction height range, and collecting distraction height data and distraction force data of the femur relative to the tibia; deriving ligament displacement data and load data; processing the collected data to produce a digital geometric model of the knee joint, wherein the model includes a ligament force versus displacement characterization curve for each of a plurality of flexion angles; using a software application, evaluating the digital geometric model of the knee in comparison to patient population data; using the software application, selecting a portion of the characterization curve that represents an optimized level of ligament tautness, based on the evaluation; and storing the digital geometric model for further use.