Offset Adapter Unit Neck Fracture Prevention
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Solution Overview
Problem
In revision total knee arthroplasty, existing offset adapter units are prone to fracture at the neck due to repetitive bending moments from axial loads, leading to increased pain and risk of reoperation.
Innovation Solution
An offset adapter unit with an expanded step in the screw connecting region and a nut with a step portion is designed to cover the adapter, enhancing the strength by distributing the load and preventing fracture at the most vulnerable part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a common offset adapter is used to connect and fix the extension stem to the femur or tibia, then the extension stem can be attached to accommodate bone defects or deformities, but the neck of the adapter is prone to fracture due to repetitive bending moments from axial loads
Solution Approach 1:
The adapter is divided into distinct segments: a head portion with a first diameter and a body portion with a second diameter. This segmentation allows each part to be optimized independently - the head for adaptability and the body for strength against bending moments.
Solution Approach 2:
The adapter employs asymmetric diameter design where the head portion has a different diameter than the body portion. This asymmetry creates a geometric configuration that resists bending moments while maintaining the offset functionality needed for bone defects.
2Device complexity
If the adapter neck is made narrower to reduce material usage, then the device complexity and material consumption decrease, but the risk of fracture at the narrowest area increases
Solution Approach 1:
Different parts of the adapter have different diameters tailored to their specific functional requirements. The body portion has a larger diameter specifically at the location subject to bending moments, providing localized strength where needed without unnecessarily increasing complexity elsewhere.
Data Source
AI summary
The present invention relates to an implant playing a role as a joint in coupling a revision implant in revision total knee arthroplasty and, more specifically, to an offset adapter unit comprising an adapter which couples a femoral member or a tibial member to a stem member in revision total knee arthroplasty; and a nut coupled to the adapter, thereby improving the strength by considering fracture occurring in the narrowest area.