Dynamic Knee Balancer Actuator for Ligament Tension
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Solution Overview
Problem
Current devices and techniques for total knee arthroplasty (TKA) surgery fail to dynamically balance ligament tension throughout the full range of knee motion, leading to instability, limited range of motion, and uneven wear of prosthetic devices, especially in minimally invasive procedures where access to the lateral side is restricted.
Innovation Solution
A femoral assembly with a stationary and adjustable member that allows for dynamic ligament tension balancing through a range of motion, using an actuator mechanism to adjust tension in the medial or lateral side without eversion of the patella, providing positional information for precise bone cuts and prosthetic component placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If minimally invasive TKA techniques are used with smaller incisions, then patient trauma is reduced and recovery time is shortened, but access to the lateral side of the knee is restricted making ligament tension balancing difficult
Solution Approach 1:
The device is divided into separate medial and lateral components that can be independently positioned and adjusted. The lateral component can be accessed and adjusted through the medial incision, allowing minimally invasive access while maintaining the ability to balance both medial and lateral ligament tensions
Solution Approach 2:
The medial component acts as an intermediary mechanism that transmits adjustment forces to the lateral component. By adjusting the medial component, the lateral ligament tension is indirectly balanced without requiring direct access to the lateral side
2Ease of operation
If traditional TKA techniques with patella eversion are used, then access to the distal femur is improved, but procedural time and rehabilitation time are increased
Solution Approach 1:
The device provides preliminary positioning and stabilization of the femoral component during the surgical procedure. Positioning features are pre-configured to guide accurate bone cuts and component placement without requiring extensive manual manipulation or patella eversion
Solution Approach 2:
The device replaces the need for mechanical patella eversion with a visualization and positioning system that works through the minimally invasive incision. Sensors and positioning features provide the necessary mechanical guidance without the harmful mechanical action of eversion
3Device complexity
If ligament tension is not dynamically balanced through full range of motion, then surgical procedure is simpler, but knee stability and range of motion are compromised
Solution Approach 1:
The device incorporates dynamic adjustment capabilities that allow ligament tension to be balanced through the full range of motion. The adjustable members can be modified while the knee is moved through flexion and extension, ensuring proper tension at all angles rather than just in a static position
Solution Approach 2:
The device provides real-time feedback on ligament tension through sensors and positioning features that indicate when proper balance is achieved. This feedback mechanism guides the surgeon in making precise adjustments to achieve optimal knee stability and range of motion
4Manufacturing precision
If precise positioning features are added to the device, then prosthetic component placement accuracy is improved, but device complexity increases
Solution Approach 1:
Positioning features are concentrated at specific critical locations on the device where they are most needed for accurate component placement. Rather than distributing complexity throughout the entire device, localization of sensing and positioning elements achieves high precision with minimal added complexity
Data Source
AI summary
A device for performing a surgical procedure on a knee comprises a femoral assembly comprising a stationary femoral member attachable to the distal femur, an adjustable femoral member movably coupled with the stationary member to adjust tension in at least one ligament of or adjacent the knee and an adjustment mechanism coupled to the assembly. The adjustable member includes at least one positioning feature that moves relative to the distal femur as the adjustable member is adjusted and identifies at least one position on the distal femur. The adjustable member is movably couplable with a tibial member engaged with a proximal tibia to allow the knee to be moved through a range of motion without removing the femoral and tibial members. The mechanism includes an actuator positioned proximate a medial or lateral portion of the adjustable member. The actuator is configured to adjust an opposite portion of the adjustable member.