Bone Screw Cross-Hole Fixation for Charcot Foot Stability
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Solution Overview
Problem
Existing bone screws for treating Charcot foot suffer from high infection risk and long-term instability due to migration from the initial implant position, compromising treatment outcomes.
Innovation Solution
A bone screw design featuring at least one transverse through-hole for pin insertion, which projects on opposite sides to constrain the screw, combined with a tightening device and centering instrument for minimally invasive pin placement, ensuring stable fixation and reduced migration risk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a bone screw is implanted to support the arches of the foot, then the structural support function is improved, but the risk of infection and long-term stability deteriorate due to migration from initial implant position
Solution Approach 1:
The bone screw is divided into three distinct portions: a head portion with threading for bone engagement, a non-threaded intermediate portion for insertion, and a tip portion with threading for compression. This segmentation allows each portion to perform its specific function optimally while working together to prevent migration and maintain long-term stability.
Solution Approach 2:
The invention employs nested structures including a tightening element that fits within an axial channel of the head portion, and a coupling mechanism where the head portion can be removably coupled to the intermediate portion. These nested elements work together to secure the screw in place and prevent migration over time.
2Strength
If a bone screw with large diameter non-threaded stem is used to support patient weight, then the load-bearing capacity is improved, but the risk of infection increases due to larger incision requirements
Solution Approach 1:
The bone screw features different threading characteristics in different portions: the head and tip portions have external threading for bone engagement and compression, while the intermediate portion is non-threaded to facilitate minimally invasive insertion. This local differentiation allows the screw to maintain load-bearing capacity while reducing incision size and infection risk.
Solution Approach 2:
The invention changes the threading parameter along the length of the screw, transitioning from threaded (head) to non-threaded (intermediate) to threaded (tip). This parameter variation enables the intermediate portion to be inserted through a smaller incision while the threaded portions provide adequate load-bearing capacity once implanted.
3Strength
If a bone screw with external threading at head and tip is used to generate bone compression, then the bone compression function is improved, but the device complexity increases due to additional structural features required to prevent migration
Solution Approach 1:
The bone screw is designed as a multi-functional device where the external threading at the head and tip portions simultaneously provides bone engagement, compression force generation, and migration prevention. The intermediate non-threaded portion serves dual purposes of facilitating insertion and acting as a spacer. This multi-functionality reduces the need for additional separate structural features.
Solution Approach 2:
The invention merges multiple functions into a single integrated screw structure. The threading pattern itself serves both compression and anchoring functions, while the intermediate portion combines insertion facilitation with structural spacing. This merging eliminates the need for separate components and reduces overall device complexity.
Data Source
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AI summary
The present invention relates to an improved bone screw(1') for the treatment of bone collapses or deformations, such as in the case of the Charcot foot, comprising a non-threaded intermediate portion (2) spaced between a tip portion (3) and a head portion (4) externally threaded; the bone screw (1') further comprising at least one transverse hole (6) arranged for inserting a corresponding at least one pin (7) to prevent the migration of said bone screw (1) when implanted into the bone. The present invention also relates to an insertion instrument (20) for inserting at least one pin (7) into at least one hole (6) of the bone screw (1').