Reference Point Wedge for UKA to TKA Conversion Alignment
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Solution Overview
Problem
During the conversion of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA), the removal of the UKA implant creates a void on the femoral condyle, making it difficult to accurately align the TKA implant due to the loss of natural reference points, often resulting in malposition and poor patient outcomes.
Innovation Solution
A reference-point providing device with a wedge and mounting flange is used to fit into the void left by the UKA implant, providing a reference point for the posterior reference guide to ensure accurate alignment and rotation of the TKA implant, which is adjustable in thickness and attachment method to accommodate different prosthetic sizes and surgical needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If UKA implant is removed to convert to TKA, then the entire articular surface can be replaced, but the natural reference points on the femoral condyle are lost making alignment difficult
Solution Approach 1:
The reference point providing device is inserted into the void left by the UKA implant before the TKA implantation process begins. This preliminary placement restores the missing anatomical reference points on the femoral condyle, enabling accurate alignment measurements to be taken before the actual TKA implant is positioned and fixed.
Solution Approach 2:
The reference point providing device acts as an intermediary element between the void left by the removed UKA implant and the alignment measurement process. It temporarily fills the space and provides the necessary reference surfaces that would otherwise be absent, allowing the alignment tools to function correctly during the conversion surgery.
2Adaptability or versatility
If UKA implant is removed, then conversion to TKA is enabled, but the void created causes difficulty in determining correct rotation and alignment
Solution Approach 1:
The reference point providing device serves as a temporary intermediary structure that bridges the gap created by UKA implant removal. It provides the necessary geometric references on the femoral condyle surface, making the alignment and rotation determination process as straightforward as in primary TKA surgeries.
Solution Approach 2:
The reference point providing device replicates the function of the natural femoral condyle surface by providing equivalent geometric reference points. It copies the essential alignment features that would naturally exist, allowing surgeons to use standard alignment techniques without needing to develop new procedures for the void condition.
3Productivity
If incorrect alignment is achieved, then surgical procedure is completed, but patient outcomes deteriorate with pain and gait disturbances
Solution Approach 1:
The reference point providing device enables real-time feedback during the alignment process by providing fixed geometric references that can be measured against. This allows surgeons to verify correct alignment and rotation before final implant fixation, ensuring that the surgical procedure completes with accurate positioning rather than relying on post-operative outcomes to indicate problems.
Solution Approach 2:
By establishing accurate alignment references before the TKA implant is permanently fixed, the reference point providing device ensures that alignment decisions are made with precise information available. This preliminary alignment verification prevents incorrect implant positioning that would lead to poor patient outcomes.
Data Source
AI summary
A reference-point providing (RPP) device for conversion of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA), has a wedge having a joint surface, a bottom flat surface, and a second surface, the second surface extending from the bottom flat surface to the joint surface at a thick end of the wedge and a mounting flange; the wedge fitting in a space remaining after removal of a UKA implant with the joint surface providing a reference point for determining alignment of a TKA implant. Converting a UKA to TKA with the RPP requires removing UKA implant from a femur of a patient, inserting the RPP and attaching it to the femur; using a posterior reference guide having a first paddle on a condyle of the femur and a second paddle on the RPP, to determine necessary alignment and rotation of the TKA implant; and removing the RPP.