Modular Femoral Sizer Gap Referencing
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Solution Overview
Problem
Traditional femoral sizers in knee arthroplasty procedures face complexity due to reliance on posterior condyles for measurement, which becomes inaccurate with varying posterior resections, making it difficult to achieve balanced flexion and extension gaps.
Innovation Solution
A modular femoral sizer system that uses the intended flexion gap height as a reference point instead of posterior condyles, allowing for accurate sizing of the femur independent of posterior resection thickness, integrated with a drill guide for precise alignment and measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional femoral sizers use posterior condyles as reference point, then measurement is straightforward, but measurement precision deteriorates when posterior resection thickness varies
Solution Approach 1:
The patent introduces a drill guide as an intermediary device that establishes a reference point on the distal femur surface, independent of the posterior condyles. This mediator transfers the reference function from the condyles to a new location that remains stable despite varying posterior resection thickness, thereby maintaining measurement precision while simplifying the sizing procedure.
Solution Approach 2:
Instead of referencing the femur from the posterior condyles (traditional approach), the patent inverts the reference strategy by using a drill guide to establish a reference point on the distal femur surface. This reversal allows accurate femoral sizing to be achieved independent of posterior resection variations, resolving the contradiction between measurement accuracy and procedure simplicity.
2Reliability
If posterior resection amount is varied to balance flexion and extension gaps, then gap balancing is achieved, but femoral sizing accuracy deteriorates with traditional sizers
Solution Approach 1:
The drill guide acts as a mediator that decouples the femoral sizing reference from the posterior condyles. By establishing a stable reference point on the distal femur surface through the drill guide, the system maintains accurate femoral size determination even when posterior resection varies to achieve gap balancing, thus resolving the contradiction between gap balancing reliability and sizing precision.
3Reliability
If surgeon manually adjusts femoral implant size based on gap matching, then gap balancing can be achieved, but procedure time and complexity increase
Solution Approach 1:
The drill guide performs the preliminary action of establishing an accurate reference point and measuring the femoral gap before femoral implant selection. By pre-establishing the correct reference and measurement, the system eliminates the need for manual adjustment and iterative gap matching, thereby reducing procedure time while maintaining gap balancing accuracy.
Solution Approach 2:
The drill guide provides direct feedback through its measurement indicators, showing the surgeon the accurate femoral size determination. This immediate feedback eliminates the need for manual adjustment iterations, reducing procedure time while maintaining the reliability of gap matching through precise, real-time measurement information.
Data Source
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AI summary
A knee arthroplasty assembly for use in a patient's knee joint including a tibia and a femur is disclosed. The assembly can include a tool (10), a first accessory (90), and a second accessory (100). The tool can include a tibial component (14) configured for placement against the tibia and a femoral component (16) configured for placement against the femur. The femoral component can be moveably coupled to the tibial component to place the patient's knee joint in tension by separating the tibia and the femur. The first accessory can be removeably coupled to the tibial component of the tool. The second accessory can be referenced to the first accessory and can have a reference indicator (114A, 114B) that references the femur for determining a size of the femur.