Locking Peg Extended Thread for Bone Extraction
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Solution Overview
Problem
Traditional locking pegs used in bone plates are difficult to remove from bone due to their unthreaded shafts, which lack the necessary axial force for extraction, making removal challenging and potentially risky for patients.
Innovation Solution
A locking peg design featuring a shaft with a threaded proximal portion and an unthreaded distal portion, where the threaded portion extends 2 to 6 revolutions into the bone, providing additional axial force for easier removal by extending the threading beyond the head of the peg.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If locking pegs have unthreaded shafts to enable quick insertion and reduce tissue damage risk, then insertion speed is improved and tissue damage risk is reduced, but removal difficulty increases significantly
Solution Approach 1:
The shaft is segmented into two distinct portions: an unthreaded distal portion for quick insertion and minimal tissue damage, and a threaded proximal portion for effective removal. This segmentation allows each portion to fulfill its specific function optimally without compromise.
Solution Approach 2:
Different portions of the shaft have different threading characteristics tailored to their specific functions. The distal portion is unthreaded to minimize tissue damage during insertion, while the proximal portion is threaded to provide axial force during removal. This local differentiation resolves the contradiction between easy insertion and easy removal.
2Object-affected harmful factors
If locking pegs have unthreaded shafts to minimize tissue damage risk, then tissue damage risk is reduced, but axial force for extraction is insufficient
Solution Approach 1:
The shaft is divided into functional segments: the unthreaded distal portion minimizes tissue damage during insertion, while the threaded proximal portion provides the necessary axial force for extraction. This segmentation resolves the contradiction between minimizing harm and providing sufficient extraction force.
Solution Approach 2:
The shaft exhibits local quality variation with different threading characteristics at different locations. The unthreaded distal portion reduces tissue damage risk, while the threaded proximal portion generates extraction force. This localized functional differentiation simultaneously addresses both requirements.
3Ease of operation
If the threaded head unscrews only a small amount from the bone plate, then the locking mechanism is disengaged, but the head does not protrude enough to be grasped for removal
Solution Approach 1:
The threaded proximal portion is designed to advance further into the bone during initial insertion, creating a reservoir of axial movement potential. During removal, this pre-positioned threading allows the head to be pulled out further as the threads disengage, providing sufficient protrusion for grasping without requiring complex removal procedures.
Data Source
AI summary
A locking peg includes a head and a shaft. The head is at the proximal end of the locking peg, and a shaft extends distally from the head to a distal end of the locking peg. The shaft has a threaded proximal portion and an unthreaded distal portion. A length of the unthreaded distal portion of the shaft is greater than a length of the threaded proximal portion of the shaft. When the locking peg is inserted into a bone through a bone plate, the threaded proximal portion of the shaft extends into the bone. This extended threading provides additional axial force to help explant the locking peg during removal of the locking peg.