Variable Angle Locking Buttress Pin Removal Mechanism
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Solution Overview
Problem
Buttress pins used in bone fixation are difficult to remove from bones once they have healed, as they tend to rotate within the bone instead of disengaging from the plate hole, making complete withdrawal impossible.
Innovation Solution
A buttress pin design featuring a threaded head and shaft with a smooth distal portion and a rounded end, including a threaded neck that engages the bone and bone plate simultaneously, allowing for easy removal by providing a clear grip for forceps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a buttress pin is designed with threading that fully engages the bone for secure fixation, then the fixation strength is improved, but the pin becomes difficult to remove as it rotates within the bone instead of disengaging from the plate hole
Solution Approach 1:
The buttress pin is divided into two distinct threaded sections: a first threading on the head for engaging the plate hole, and a second threading on the shaft for engaging the bone. This segmentation allows each threading to serve its specific function independently, enabling the pin to be secured during insertion while facilitating removal by disengaging from the plate hole first
Solution Approach 2:
The first threading acts as an intermediary mechanism between the buttress pin and the plate hole. During insertion, this intermediary threading engages first to guide and secure the pin in the plate, but during removal, it allows the pin to disengage from the plate hole before the second threading disengages from the bone, preventing rotation and enabling complete withdrawal
2Strength
If the threading extends over the entire length of the shaft, then the fixation strength is improved, but the pin cannot be removed as the threading prevents disengagement from the plate hole
Solution Approach 1:
The threading is segmented into two distinct sections along the shaft length: first threading on the head portion for plate hole engagement, and second threading on the distal shaft portion for bone engagement. This spatial segmentation ensures that not the entire length is threaded, allowing the unthreaded intermediate section to facilitate disengagement from the plate hole during removal
Solution Approach 2:
Different portions of the shaft have different threading characteristics: the head has first threading optimized for plate engagement, while the distal shaft has second threading optimized for bone engagement. This local differentiation allows each section to perform its specific function while enabling removal by creating a disengagement sequence
3Strength
If the distal end of the threading is positioned close to the distal end of the shaft, then the fixation strength is improved, but the pin becomes difficult to remove as there is insufficient space for disengagement
Solution Approach 1:
The first threading is positioned to engage the plate hole in advance during insertion, securing the pin before the second threading engages the bone. During removal, this preliminary positioning of the first threading allows it to disengage first, creating the necessary space and sequence for complete pin withdrawal without rotation
Solution Approach 2:
The threading arrangement creates a temporal and spatial sequence in the engagement and disengagement process. By positioning the first threading at the proximal end and second threading at the distal end, the invention transforms the removal process into a staged event where disengagement occurs in a specific sequence along the longitudinal dimension of the pin
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates the removal of the buttress pin from the bone without damaging the surrounding tissue, enabling secure fixation and easy retrieval once healing is complete.
Implementation Method 1
the head comprising a rounded outer profile and including first threading and a shaft extending distally from the head, the shaft including second threading extending over at least a portion of a length thereof
Data Source
Figure 1~2
Figure 3
AI summary
A buttress pin for fixing an implant to a bone, comprises a head at a proximal end, the head comprising a rounded outer profile and including first threading and a shaft extending distally from the head, the shaft including second threading extending over at least a portion of a length thereof, a position of a proximal end of the second threading along the shaft being spaced from a distal end of the first threading by a distance equal to a distance between a proximal end of a hole in an implant to be anchored to a bone via the buttress pin and a surface of the bone when the implant is in a target position on the bone.