Half Pins for External Fixators with Hydroxyapatite Coating
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Solution Overview
Problem
Existing external fixator technologies face challenges in optimizing tissue hygiene, minimizing contamination and infection, while providing accurate bone fixation, durability, and promoting bone growth and healing, with a need for versatile and efficient half pins that can facilitate easy insertion and removal while maintaining mechanical strength and load-bearing capacity.
Innovation Solution
The development of half pins with a minimally porous hydroxyapatite coating, variable thread pitch, constant major diameter threads, and a truncated or rounded tip, along with a titanium pin cube for secure attachment, which provides a hygienic seal and antimicrobial properties while allowing easy removal and promoting bone growth through controlled compression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydroxyapatite coating is applied to the half pin, then antimicrobial properties and tissue integration are improved, but manufacturing complexity increases
Solution Approach 1:
The patent applies a hydroxyapatite coating to the half pin, creating a composite structure that combines the mechanical strength of the metal pin with the biological compatibility and antimicrobial properties of hydroxyapatite. This composite approach resolves the contradiction by adding functional properties without fundamentally changing the core pin structure.
Solution Approach 2:
The hydroxyapatite coating is applied with controlled porosity to allow tissue ingrowth while maintaining antimicrobial barriers. The porous structure enables biological integration while the coating itself provides the protective function, resolving the contradiction between reliability improvement and manufacturing complexity.
2Object-affected harmful factors
If the half pin tip is truncated or rounded, then tissue damage during insertion is reduced, but anchoring capability may be compromised
Solution Approach 1:
The half pin features a truncated or rounded tip to reduce tissue damage during insertion, while the shaft retains full threading for anchoring capability. This local differentiation of properties resolves the contradiction by applying different geometries to different portions of the pin based on functional requirements.
3Reliability
If variable thread pitch is implemented, then bone compression and growth stimulation are improved, but manufacturing precision requirements increase
Solution Approach 1:
The half pin implements variable thread pitch along its length, transitioning from coarser pitch at the distal end for initial anchoring to finer pitch at the proximal end for compression and growth stimulation. This dynamic variation in thread geometry resolves the contradiction by providing different mechanical functions at different locations along 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
The hydroxyapatite-coated half pins effectively prevent contamination, facilitate easy insertion and removal, and stimulate bone growth by applying controlled compression, enhancing patient comfort and the effectiveness of external fixator systems.
Implementation Method 1
The present half pin is also distinctively provided with a particular hydroxyapatite coating on a specific portion—and majority surface—thereof, which has a porosity of 5% or less but must indeed be porous, with a pore size no greater than 10 micrometers
Implementation Method 2
the hydroxyapatite coating on threads and at least a portion of the non-threaded shaft nearest the head end, in use forms a hygienic seal between the pin surface and the skin and muscle (and fascia and adipose, etc.) adjacent its insertion
Implementation Method 3
the threaded portion of the shaft, when inserted in the bone, do compress the bone, which in turn enhances the grip of the threads in the bone and stimulates bone growth
Implementation Method 4
the ability of the hydroxyapatite to form a de facto seal for hygiene purposes, while simultaneously performing a 'quick release' function where the non-threaded portion of the half pin contacted the skin and muscle areas of half pin insertion
Data Source
AI summary
The invention is a half pin for use in conjunction with external fixators, in which the half pin has a thin hydroxyapatite coating over a substantial portion thereof, a not-sharp hole-finding tip, and a variable pitch pattern in the threaded portion of the half pin. The hydroxyapatite coating must be thin—40-70 microns, deposited by plasma spray—and with limited porosity and pore size, and must extend not only over all the threads of the half pin but also a substantial portion of the unthreaded shaft proximal to the threaded end. The invention also includes a pin cube for use in association with the coated half pins. Wires may also be coated with the hydroxyapatite coating.