Mid-Flexion Knee Balancing for Stable Arthroplasty Kinematics
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Solution Overview
Problem
Total knee arthroplasty (TKA) procedures often result in abnormal kinematic motion patterns due to the loss of cruciate ligaments and improper soft tissue balancing, leading to mid-flexion instability and unnatural sliding motions in the knee joint, which can cause instability and discomfort for patients.
Innovation Solution
A joint distractor device and method for soft tissue balancing at mid-flexion angles between full extension and 90 degrees, allowing for precise alignment and resection of bones to mimic natural knee kinematics by using paddles and a measurement tool to determine the necessary gap for orthopedic implants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional TKA procedures are performed without mid-flexion soft tissue balancing, then the surgical process is simpler and faster, but the knee joint exhibits abnormal kinematic motion patterns and mid-flexion instability
Solution Approach 1:
The patent applies preliminary action by performing soft tissue balancing at mid-flexion (30-60 degrees) before completing the bone resections and implant placement. The distractor device is inserted and soft tissue tension is assessed and adjusted during the early stages of surgery, allowing the surgeon to establish proper ligament balance before finalizing the bone cuts. This preliminary soft tissue balancing prevents abnormal kinematic patterns and mid-flexion instability that would otherwise require complex revisions later.
2Ease of operation
If soft tissue balancing is performed at mid-flexion using a distractor device, then natural knee kinematics are restored, but the device complexity and surgical time increase
Solution Approach 1:
The distractor device incorporates self-service features through its automatic gap measurement and indication system. The device includes a measurement tool that automatically calculates the required bone resection depth based on the soft tissue balance achieved at mid-flexion. The device provides visual or digital indicators that guide the surgeon in making the appropriate bone cuts, eliminating the need for complex manual measurements and calculations. This self-service capability streamlines the workflow and reduces surgical time despite the additional balancing step.
3Object-affected harmful factors
If the femoral condyles are allowed to slide abnormally in TKA, then the implant design is simpler, but the patient experiences instability and discomfort
Solution Approach 1:
The patent implements feedback through the distractor device's measurement and indication system that provides real-time information about soft tissue tension and gap measurements at mid-flexion. The device gives the surgeon feedback on whether the soft tissues are properly balanced by indicating the required bone resection depth. This feedback mechanism ensures that the knee joint achieves natural kinematics with proper femoral condyle rollback rather than abnormal sliding, thereby eliminating patient discomfort and instability without requiring overly complex implant designs.
Data Source
AI summary
Methods and devices are disclosed for soft tissue balancing of a knee joint during an arthroplasty procedure that include balancing the knee joint at or near mid-flexion, while maintaining the rotational position of the femur with respect to the tibia that replicates proper kinematic placement of these bones. Also disclosed are methods and devices for soft tissue balancing of a knee joint during an arthroplasty procedure that include balancing the knee joint at or near mid-flexion using one or more expansion devices that are not actively requiring monitoring and/or recording of forces applied by the bodily tissues, but instead uses incremental changes in actual length/height of the expansion device to determine whether the joint is properly tensioned or too lax.