Non-Circular Allograft Bone Graft Shaping Instruments
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Solution Overview
Problem
Current knee replacement surgery techniques are limited by the inability to use non-circular shaped allograft bone plugs, which do not match the oval or oblong arthritic cartilage damage patterns, and lack instruments to accurately size and shape donor femur implants for precise fitting in osteoarthritis distal femur resurfacing procedures.
Innovation Solution
The development of sizing guides, osteotomes, and templates that allow for the extraction and shaping of non-circular allograft bone and cartilage plugs from donor femurs, enabling precise matching and cutting to fit the recipient's femoral size and curvature, facilitating the use of oval or oblong implants in knee replacement surgery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If circular allograft bone plugs are used, then the implant can be easily manufactured and implanted, but the shape does not match the oval or oblong arthritic cartilage damage pattern
Solution Approach 1:
The implant extraction process is segmented into multiple cutting steps using specialized instruments. The allograft is first outlined, then cut in half, and finally shaped into the precise oval or oblong configuration needed to match the cartilage damage pattern, rather than attempting to extract a single complex shape in one step
Solution Approach 2:
The cartilage damage pattern is outlined and marked on the donor femur before any cutting begins. This preliminary action defines the exact shape and size of the allograft needed, ensuring it will match the recipient's defect while guiding subsequent cutting steps
2Shape
If non-circular allograft plugs are extracted, then the implant shape matches the arthritic damage pattern, but specialized instruments and techniques are required
Solution Approach 1:
A template instrument serves as an intermediary between the outlined cartilage damage pattern and the final allograft shape. The template is placed over the outline and guides the cutting instruments to create the precise non-circular shape needed, translating the desired geometry into actionable cutting paths
Solution Approach 2:
The shaping process is divided into sequential cutting operations using different specialized instruments. Osteotomes are used for initial shaping, followed by rasp instruments for fine-tuning the contours, allowing complex non-circular shapes to be created through multiple simpler steps rather than one complex operation
3Manufacturing precision
If precise sizing and shaping instruments are used, then the implant fits the recipient's femoral size and curvature accurately, but the procedure becomes more complex
Solution Approach 1:
The sizing instrument is designed to perform multiple functions: it measures the recipient's femoral defect dimensions, determines the appropriate allograft size, and guides the positioning and orientation of the implant. This multi-functionality consolidates several separate measurement and alignment steps into a single versatile tool
Solution Approach 2:
The recipient's femoral defect is precisely measured and characterized before the donor femur is processed. This preliminary assessment of size, shape, and curvature allows the surgeon to select and prepare the appropriate allograft dimensions in advance, ensuring accurate fit without requiring complex intraoperative adjustments
Data Source
AI summary
A technique for knee replacement surgery that allow for the removal of an oval oblong-shaped allograft bone and cartilage plug from a donor distal femur. The technique uses instruments including (i) sizing guides to match the recipient's femoral size and curvature to that of a donor femur (the sizing guides also acting as a wide pin placement template for the donor distal femur); (ii) osteotomes that cut the curved and straight portions of the implant shape (these may be disposable or reusable); and (iii) templates that fit over the guide pins and have openings to allow the osteotomes to cut the donor femur plug to the correct size, shape and depth. The instruments allow for a non-circular shape to be extracted from a donor femur for use in a bone-saving osteoarthritis distal femur resurfacing procedure.