Robotic Knee Soft Tissue Balancing with Adjustable Spacers
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Solution Overview
Problem
Conventional methods for soft tissue balancing in orthopedic surgeries, such as knee arthroplasty, lack precision and accuracy due to manual evaluations, leading to potential joint instability and errors in soft tissue tension assessments.
Innovation Solution
The integration of a robotic system with an eLibra device and adjustable spacers that wirelessly transmit force and tension data, allowing for precise soft tissue balancing by adjusting medial and lateral compartments of the knee using sensors and optical tracking, enabling accurate planning and execution of bone cuts and implant sizing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual evaluation methods are used for soft tissue balancing, then the surgical process is simple and quick to perform, but the measurement precision and accuracy of soft tissue tension assessment deteriorates
Solution Approach 1:
The patent replaces manual mechanical evaluation with a robotic system that uses sensors and optical tracking to measure soft tissue tension. The robotic arm equipped with force sensors and optical trackers objectively quantifies ligament tension during range of motion tests, eliminating the subjectivity and imprecision of hand-based assessment while providing detailed numerical data for soft tissue balancing decisions.
Solution Approach 2:
The patent introduces trial spacers as intermediary devices between the robotic system and the patient's knee joint. These spacers are placed in the joint space to maintain specific gap distances during range of motion testing, allowing the robotic system to indirectly measure soft tissue tension through controlled mechanical interaction. The spacers serve as mediators that enable precise measurement without direct contact with sensitive tissues.
2Reliability
If conventional manual methods are used, then the surgical procedure is faster to perform, but the reliability of joint stability assessment deteriorates
Solution Approach 1:
The patent performs preliminary soft tissue balancing assessments using the robotic system before final implant placement. By conducting range of motion tests with trial spacers and measuring ligament tension in advance, the surgical team can identify and correct soft tissue imbalances before committing to the final implant configuration. This preliminary action increases the reliability of joint stability assessment by allowing multiple measurements and adjustments prior to the irreversible final implantation.
Solution Approach 2:
The patent implements a feedback loop where the robotic system continuously measures soft tissue tension during range of motion testing and provides real-time data to the surgical team. The system measures ligament tension at various angles of knee flexion and extension, compares these measurements against target values, and allows for iterative adjustments of trial spacers or bone cuts. This feedback mechanism enhances the reliability of joint stability assessment by enabling data-driven decision-making and verification of balancing outcomes.
3Manufacturing precision
If robotic systems with sensors and optical tracking are implemented, then the manufacturing precision of bone cuts and implant positioning is improved, but the device complexity and cost increase
Solution Approach 1:
The robotic system performs multiple functions within a single integrated platform: it positions and guides bone cuts with high precision, places trial spacers accurately, conducts range of motion testing, measures soft tissue tension, and guides final implant positioning. The optical tracking system and force sensors serve multiple measurement purposes simultaneously. This multi-functionality justifies the device complexity by consolidating numerous surgical tasks into one versatile system, improving overall manufacturing precision across all these functions.
Solution Approach 2:
The robotic system divides the complex task of knee arthroplasty into discrete, measurable steps: initial bone surface registration, precise bone cut execution, trial spacer placement, range of motion testing with tension measurement, and final implant positioning. Each step is independently controlled and measured by the robotic system with sub-millimeter accuracy. This segmentation allows for precise control and verification of each surgical action, improving manufacturing precision while making the complex process more manageable and predictable.
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 approach enhances the precision and accuracy of soft tissue balancing, reducing errors and improving joint stability by providing real-time feedback and allowing for adjustments during the surgical procedure, thereby ensuring optimal tension and alignment throughout the range of motion.
Implementation Method 1
a force sensor device to: measure a force applied to the trial device
Implementation Method 2
using sensors and optical tracking
Data Source
AI summary
A system and method may be used to evaluate soft tissue. A knee arthroplasty soft tissue evaluation may use an adjustable spacer, such as varying sized physical spacers or an inflatable bladder, along with a sensor to measure force, pressure, gap distance, or the like during a range of motion test. A method may include maintaining an equal pressure or gap distance for a medial component and a lateral component of an adjustable spacer during a range of motion test. Information, including, for example a maximum or minimum gap distance or pressure may be determined during the range of motion test. The determined information may be output for display or used to update a surgical plan.