Modular Femoral Sizing Guide for Minimally Invasive Knee Arthroplasty
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Solution Overview
Problem
Existing methods for determining the anterior-posterior dimension of the femur during knee arthroplasty, particularly in minimally invasive procedures, face challenges such as skin tightening around small incisions, making it difficult to insert instruments accurately and potentially leading to errors, and requiring additional surgical steps that complicate the procedure and recovery.
Innovation Solution
A modular instrument comprising discrete components that can be inserted separately through a smaller incision, allowing for assembly within the knee joint, featuring a sliding mechanism with an implant size indicator that can be locked in place, enabling accurate measurement of the anterior-posterior dimension without the need for extensive skin manipulation or additional surgical steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a small incision is made in the knee joint for minimally invasive procedures, then patient recovery time is reduced and tissue damage is minimized, but the skin surrounding the incision tightens when the knee is flexed, making it difficult to insert the sizing guide accurately
Solution Approach 1:
The sizing guide is divided into multiple discrete components: a base component that contacts the posterior femoral condyles, a stylus component with a measurement indicator, and a locking mechanism. These separate components can be inserted through the small incision individually and then assembled within the knee joint to form the complete measurement device.
Solution Approach 2:
The stylus component is designed to be received within a receiving structure on the base component, with the measurement indicator positioned within the assembly. This nested configuration allows the entire sizing guide to be compact enough for minimally invasive insertion while maintaining its measurement functionality when assembled.
2Measurement precision
If the knee joint is placed in 90° flexion to measure the anterior-posterior dimension, then the measurement can be performed as described in prior art, but the incision moves distally away from the distal femur, making it difficult for the surgeon to visually assess stylus positioning
Solution Approach 1:
The measurement indicator on the stylus component includes visual features such as color-coded markings or contrasting colors that allow the surgeon to easily identify the measurement reading and confirm proper stylus positioning on the anterior cortex of the distal femur, even when direct visualization is limited by the incision position.
3Ease of operation
If an additional surgical step of removing an initial section of the anterior cortex is performed to provide additional space, then the sizing guide can be inserted more easily, but further instrumentation is required and the final implant positioning may be influenced
Solution Approach 1:
The sizing guide is divided into multiple discrete components: a base component that contacts the posterior femoral condyles, a stylus component with a measurement indicator, and a locking mechanism. These separate components can be inserted through the small incision individually and then assembled within the knee joint to form the complete measurement device.
Data Source
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AI summary
An instrument for use in determining an anterior-posterior dimension of a femur during a minimally invasive surgical procedure includes a body having a base and a member extending upwardly from the base, said member providing a first part of a sliding mechanism. A stylus includes a stylus support providing a second part of a sliding mechanism which can engage with the member to allow relative sliding movement between the stylus and base, and a stylus member mounted on the stylus support. An implant size indicator interacts with the sliding mechanism to be moved relative to a scale by the member to indicate a size of an implant corresponding to the relative positions of the body and stylus.