Rotary Mill Guide Portion for Precision Bone Resection
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Solution Overview
Problem
In partial knee replacement surgery, the manual removal of anterior bone using a bone chisel is prone to errors, leading to uneven bone edges and variable bone removal, which can result in impingement and failure of the polyethylene bearing component.
Innovation Solution
A rotary mill with a guide portion featuring alignment pegs matching the prosthesis component, allowing precise bone removal without additional bone preparation, using existing peg holes for fixation and incorporating depth stops for accurate bone resection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bone chisel is used to manually remove anterior bone, then the procedure is simple and requires minimal equipment, but the bone removal is non-uniform and the amount of bone removed is uncertain and variable
Solution Approach 1:
A guide portion is introduced as an intermediary device between the surgeon and the bone removal process. This guide portion includes a guide body with alignment features that mate with prosthesis component features, and a guide peg that directs the milling cutter. The intermediary guide ensures precise, uniform bone removal while maintaining procedural simplicity through its straightforward attachment and guidance mechanism.
2Manufacturing precision
If a guide portion with alignment features is used to precisely guide bone removal, then manufacturing precision of bone resection is improved, but device complexity increases
Solution Approach 1:
The guide portion is designed to be universal and multi-functional. The guide body incorporates alignment features that mate with standard prosthesis component features (such as peg holes or flange recesses), allowing the same guide structure to work with different prosthesis components. The guide peg serves multiple functions: guiding the milling cutter, limiting its travel distance, and ensuring proper orientation. This multi-functionality reduces the need for multiple specialized tools.
Solution Approach 2:
The guide portion utilizes the existing structure of the prosthesis component itself as part of the guidance system. The alignment features on the guide body nest within or mate with corresponding features on the prosthesis component (such as inserting the guide body into the prosthesis or mating alignment pegs with prosthesis peg holes). This nesting approach integrates the guidance function into the existing component structure rather than adding entirely separate guidance mechanisms.
3Manufacturing precision
If conventional guided mills requiring a dedicated guide rod hole are used, then precise bone removal is achieved, but additional bone preparation is required
Solution Approach 1:
The guide portion is designed to utilize existing prosthesis component features (peg holes, flange recesses) for attachment and alignment, eliminating the need for dedicated guide rod holes. The alignment features on the guide body can mate with these pre-existing features, allowing the guidance system to function using already-prepared bone structures without requiring additional bone removal or preparation steps.
Data Source
AI summary
A rotary mill is disclosed comprising a body portion (4) having a milling surface (10) and a central bore (30) extending along an axis of rotation (18) of the body portion (4); and a guide portion (6) having a guide body (22) and a guide peg (24) extending from the guide body (22), the guide peg (24) operable to be received in the central bore (20) of the body portion (4), the guide body (22) having at least one alignment feature (28, 30) which is the same as that of a prosthesis component. A method of implanting a unicondylar femoral component is also disclosed, the method comprising, a) reaming the femoral condylar surface to accept the unicondylar femoral component; b) drilling peg holes for affixing the unicondylar femoral component; c) affixing a guide portion of a rotary mill onto the prepared condylar surface using the drilled peg holes; d) reaming a portion of bone anterior to the affixed guide portion; e) removing the guide portion from the bone; and f) affixing a unicondylar femoral component to the prepared condylar surface.