Unicondylar Tibial Implant Cutting Guides for Precise Keel Placement
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Solution Overview
Problem
Traditional partial knee arthroplasty methods face challenges in accurately and precisely positioning the tibial keel within the bone slot, leading to potential interference with the cortical bone wall and increased stress, which can result in fractures.
Innovation Solution
A cutting guide slot with T-shaped ends is used, featuring perpendicular walls at the ends of the longitudinal slot to allow for precise placement of the keel, avoiding interference with the cortical bone wall by using a reciprocating saw blade that engages flush with these ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional cutting guides with rounded slot ends are used, then the cutting process is simpler, but the keel placement precision deteriorates leading to cortical bone contact and stress concentration
Solution Approach 1:
The cutting guide slot is segmented into multiple functional zones: a longitudinal portion for guiding the saw blade, and perpendicular end portions forming T-shaped ends. This segmentation allows the cutting guide to provide both simplified operation and precise keel placement by creating distinct functional regions within the slot structure.
Solution Approach 2:
The T-shaped ends act as intermediary reference features between the cutting guide and the reciprocating saw blade. The perpendicular end walls provide fixed reference points that mediate the positioning relationship, ensuring repeatable and precise keel placement while maintaining surgical simplicity.
2Reliability
If the slot width is increased to allow press-fit configuration, then the keel fixation is improved, but the risk of cortical bone contact increases
Solution Approach 1:
The slot dimensions are precisely controlled with specific parameter ranges: the longitudinal portion length is 15-30mm, the end wall extensions are 5-10mm perpendicular to the longitudinal axis, and the slot width matches the keel dimensions. These parameter changes enable press-fit fixation while maintaining safe distance from cortical bone through accurate dimensional control.
3Productivity
If imprecise keel placement occurs, then the surgical procedure is faster, but undesirable stress on cortical bone increases leading to fracture risk
Solution Approach 1:
The T-shaped ends are pre-formed in the cutting guide slot before surgery. This preliminary action creates built-in reference features that guide the reciprocating saw blade to the exact desired position, eliminating the need for additional positioning steps and ensuring accurate keel placement that protects cortical bone strength.
Data Source
AI summary
A tibial implant cutting guide comprises a plate to engage a resected surface and an elongate slot extending through the plate along an axis and having first and second longitudinal walls extending parallel to the axis, and a first end wall perpendicular to the axis, the first and second longitudinal walls are spaced apart by a distance and the first end wall is at least as wide as the distance. A method of arthroplasty comprises resecting a tibia to form a resected surface, advancing a cutting head in a cutting slot of a plate to engage flush with a flat first end of the cutting slot to form a bone channel, and inserting a keel into the bone channel. A method of manufacturing a tibial template comprises forming a longitudinal cutting slot in a plate and forming a widening of the cutting slot at an end of the cutting slot.