Rotary Mill Guide Portion for Precise 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 impingement of the polyethylene bearing component on femoral condylar bone tissue, causing post-operative pain, damage, and increased wear due to the lack of precision and uniformity in bone edge removal.
Innovation Solution
A rotary mill with a guide portion having alignment features matching the prosthesis component, allowing precise bone removal without additional bone removal, using pre-drilled peg holes for fixation and featuring a guide peg that adjusts to ensure accurate bone resection, minimizing the risk of impingement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bone chisel is used to manually remove anterior bone, then the surgery can be performed with simple equipment, but the bone removal is non-uniform and imprecise leading to impingement and post-operative complications
Solution Approach 1:
A guide portion is introduced as an intermediary element that interfaces between the rotary mill and the bone. The guide portion includes alignment features that mate with pre-drilled peg holes, serving as a mediator to transfer precise positioning information from the prosthesis component to the bone resection process, thereby achieving accurate bone removal without requiring complex specialized equipment
Solution Approach 2:
Peg holes are drilled in advance during the prosthesis preparation phase, creating pre-prepared fixation features before the actual bone resection. This preliminary action establishes precise reference points that guide subsequent bone removal, ensuring accuracy without adding complexity to the resection equipment itself
2Manufacturing precision
If conventional guided mills requiring dedicated drill holes are used, then precise bone removal can be achieved, but additional bone must be removed to create holes for the guide rod
Solution Approach 1:
The guide portion is designed with multi-functionality: the alignment features serve dual purposes of both guiding the rotary mill for precise bone removal and providing fixation points for the guide portion itself. This eliminates the need for separate dedicated guide holes, as the same peg holes used for prosthesis fixation also serve as guide references, thereby preventing additional bone loss
Solution Approach 2:
The functions of guidance and fixation are merged into a single integrated guide portion structure. The alignment features that guide the milling operation are combined with the fixation features that secure the guide to the bone, eliminating the need for separate guide holes and reducing total bone loss
3Device complexity
If manual bone chiseling is used, then equipment simplicity is maintained, but the bearing component may impinge on femoral condylar bone tissue causing pain and wear
Solution Approach 1:
The manual mechanical chiseling process is replaced with a rotary mill system that provides controlled, precise bone removal. The substitution of manual chopping action with rotary milling enables accurate shaping of the bone surface to prevent impingement, while the guide portion ensures the milling occurs at the correct location without requiring complex automated systems
Data Source
AI summary
A rotary mill is disclosed comprising a body portion (4) having a milling surface (10) and a central bore (20) 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.