Mid-Flexion Joint Distractor for Knee Arthroplasty Stability
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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, leading to mid-flexion instability and unnatural sliding of femoral condyles, which are not adequately addressed by current balancing methods that focus on full extension or 90 degrees of flexion.
Innovation Solution
A joint distractor device and method for soft tissue balancing at mid-flexion angles between full extension and 90 degrees, allowing precise alignment and resection of bones to mimic natural knee kinematics by tensioning soft tissues before principal bone cuts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft tissue balancing is performed at full extension or 90 degrees of flexion, then the knee joint can be stabilized at these positions, but mid-flexion instability and abnormal kinematic motion patterns persist
Solution Approach 1:
The patent applies preliminary action by performing soft tissue balancing at mid-flexion (30-60 degrees) before final implant positioning. This intermediate balancing step establishes proper soft tissue tension at the critical mid-flexion position where traditional methods fail, preventing mid-flexion instability while maintaining natural kinematic motion patterns throughout the full range of motion.
2Ease of manufacture
If traditional TKA balancing methods are used focusing on full extension or 90 degrees of flexion, then surgical procedure is simplified, but abnormal sliding of femoral condyles and mid-flexion instability occur
Solution Approach 1:
The patent segments the balancing procedure into distinct phases: initial balancing at mid-flexion (30-60 degrees), followed by final positioning at full extension and 90 degrees of flexion. This segmentation allows each phase to address specific functional requirements, with mid-flexion balancing establishing natural kinematics and subsequent phases optimizing stability at extreme positions, thereby improving overall joint functionality without excessive complexity.
3Ease of operation
If cruciate ligaments are removed during TKA, then implant placement is facilitated, but natural kinematic motion patterns are lost and abnormal sliding occurs
Solution Approach 1:
The patent applies parameter changes by modifying the balancing parameters (soft tissue tension, gap measurements) at mid-flexion angles (30-60 degrees) rather than at full extension or 90 degrees of flexion. This parameter change in the balancing reference position restores natural kinematic motion patterns and prevents abnormal sliding of femoral condyles, even when cruciate ligaments are removed, because it establishes correct soft tissue tension at the critical mid-flexion position where natural kinematics occur.
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.