Flipping-Type Graft Fixation Device with Sliding Loop
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Solution Overview
Problem
Flipping-type graft fixation devices require the bar to be passed completely outside the tunnel, leading to reduced contact between the graft and bone, potentially slowing the healing process due to increased motion of the graft within the tunnel.
Innovation Solution
A method involving a graft construct draped over a loop from a fixation buckle, where the buckle is pulled up through the bone tunnel, rotated to prevent re-entry, and secured with a sliding loop mechanism to minimize the gap between the graft and bone, using an elongated body with slots and a tang to guide the loop to a midpoint position for secure fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the bar is passed completely outside the tunnel to initiate flipping, then the bar can be rotated to prevent re-entry, but the suture loop falls back into the tunnel by about 50% of the bar length, decreasing graft contact with bone
Solution Approach 1:
The patent changes the flipping mechanism from a 90-degree rotation in three-dimensional space to a planar flip within the tunnel plane. The bar is designed to flip 180 degrees within the tunnel rather than rotating outside the tunnel, maintaining the loop's position and preventing it from falling back into the tunnel.
Solution Approach 2:
The bar includes pre-formed features such as a cam surface and engagement surface that enable the flipping action to occur within the tunnel. The cam surface is positioned to engage the loop and guide it through the flipping motion, ensuring the loop remains positioned correctly throughout the process.
2Ease of operation
If longer suture loop lengths are used to accommodate the flipping motion, then the bar can be flipped outside the tunnel, but the graft motion within the tunnel increases, potentially slowing the healing process
Solution Approach 1:
The patent confines the flipping motion to the tunnel plane rather than allowing three-dimensional rotation outside the tunnel. This dimensional constraint ensures that the loop does not gain excessive length and that graft motion within the tunnel is minimized, promoting stable healing.
3Reliability
If the bar is flipped approximately 90 degrees outside the tunnel, then the bar will not pass back through the tunnel, but the suture loop falls back into the tunnel by about 50% of the bar length
Solution Approach 1:
The patent achieves one-way fixation by flipping the bar 180 degrees within the tunnel plane rather than rotating 90 degrees outside the tunnel. The cam surface and engagement surface work together to guide the loop through the flipping motion, ensuring precise positioning and preventing the loop from falling back into the tunnel.
Solution Approach 2:
The bar includes pre-formed cam and engagement surfaces that are designed to guide the loop through the flipping motion. These features are positioned and dimensioned to ensure the loop reaches the correct position during the flip, eliminating the need for the loop to fall back into the tunnel.
Data Source
AI summary
A buckle useful for cortical fixation has a graft retention loop slidably affixed thereto for movement from a first position adjacent a first end of the buckle to a second position at about the midpoint of the buckle. The buckle, with a graft over the loop, is drawn up lengthwise through a bone tunnel through a tibia and then flipped sideways to rest against the surface of the bone with the loop and graft depending back into the tunnel. The sliding attachment of the loop permits flipping of the buckle minimizes the flipping distance, which is the excess amount of the loop which must be pulled free of the tunnel to allow the buckle to be flipped sideways.