Knee Tensioner-Balancer for In-Place Patella Gap Balancing
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Solution Overview
Problem
Current state-of-the-art gap balancing devices for total knee arthroplasty are complex, large, and do not enable balancing with the patella in-place, making it difficult to achieve proper balance and symmetry in flexion and extension gaps.
Innovation Solution
A tensioner-balancer apparatus and method for evaluating a human knee joint, incorporating a baseplate and top plate with force sensors, capable of measuring gap distances, angles, and applying loads to balance the joint, and a robot arm for precise cutting and implant placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current state-of-the-art gap balancing devices are used, then measurement capability is provided, but device complexity increases and ease of operation deteriorates
Solution Approach 1:
The tensioner-balancer is divided into separate functional modules: a tensioner component for applying distraction force, a balancer component for measuring gap distances, and interface components for bone engagement. This segmentation allows each module to be optimized independently and simplifies the overall device structure compared to integrated prior art devices.
Solution Approach 2:
The tensioner-balancer combines multiple functions into a single device: it can distract the joint, measure gap distances, measure angles, and apply controlled loads. This multi-functionality eliminates the need for multiple separate devices while maintaining measurement precision and reducing device complexity.
2Measurement precision
If current gap balancing devices are used, then some measurement capability is provided, but ease of operation with patella in-place deteriorates
Solution Approach 1:
The tensioner-balancer serves as an intermediary device that can be inserted between the femur and tibia to provide measurement and distraction functions. Its compact design allows it to fit within the joint space without requiring patellar removal, facilitating ease of operation while maintaining measurement precision.
3Manufacturing precision
If precise gap measurement is achieved, then surgical outcome is improved, but device complexity increases
Solution Approach 1:
The device replaces complex mechanical measurement systems with simpler sensor-based measurement. Force sensors and displacement sensors provide precise gap and angle measurements through electrical signals rather than complex mechanical linkages, reducing device complexity while maintaining manufacturing precision.
Data Source
AI summary
A method of evaluating a human knee joint including a femur bone, a tibia bone, and ligaments. The method includes: inserting into the joint a tensioner-balancer that includes at least one force sensor; providing an electronic receiving device; moving the knee joint through at least a portion of its range of motion; using the electronic receiving device to collect data from the at least one force sensor; processing the collected force data to produce a digital geometric model of the knee joint, wherein the data includes: a medial spline representing a locus of points of contact of a medial condyle of the femur F with the tensioner-balancer, over a range of knee flexion angles; and a lateral spline representing the locus of points of contact of the femur F with the tensioner-balancer, over a range of knee flexion angles; and storing the digital geometric model for further use.