While generally not required by medical device regulations, it is often a nice touch to add electropolishing and laser marks to your K-Wire project. The electropolishing will give it a nice clean and bright finish. The laser marks add functionality for doctors by adding depth markers so they know how far a guide wire has gone in.
The process for Modern Grinding to make a K-Wire is to first take a raw piece of stainless steel wire with the clients designated diameter. Next we grind a trocar tip (and threads if desired). We will then cut the second end to length and soft grind this end so that there are no burrs or hard edges. Next we electropolish, then laser mark, then passivate per ASTM A967 and send out to our happy clients.
Below is a photo of a threaded k-wire with electropolishing and a smooth k-wire with a laser marked depth marker. If you have questions about this product or process or if you need help with your next project don’t hesitate to contact us.
K-Wire with Electropolish and Laser Mark
At Modern Grinding, we have customers ask for Spade Tip K-Wires. This is normally followed by a pause and then when we ask what they mean by spade tip, they aren’t really sure. The wikipedia definition of spade tip is “a tool designed primarily for the purpose of digging” Usually when a customer asks us for a spade tip, they mean a sharp tip for digging into bone.
There are two sharp tips that we typically manufacture, trocar tip and diamond tip. Trocar is far and away the most typical spade tip k-wire. Diamond tip is less prevalent but still available. We have also had a customer ask about grinding “flats” on the back end of the k-wire for drilling purposes and he referred to the flats as a spade tip.
This post was trying to dispel the rumor of what spade tip k-wire is. We may ask you to clarify what you mean by spade tip, there are many different types.
We have been asked a couple times whether or not K-Wire is MRI compatible. We cannot speak for all K-Wires since K-Wires can come in different shapes and sizes. The most common K-Wire is made of Stainless Steel. Nitinol is the second most common, we typically see it in about 8% of the K-Wires we make.
It is possible for K-Wires to be MRI compatible. Often times the distributor or OEM you purchased from will have labeling which describes the compatibility of the K-Wire you are using. If you are unsure, make sure to contact the K-Wire OEM for additional information.
Here are several good articles discussing this topic:
Make sure to consult your MRI operator prior to the scan if you have a K-Wire implant in your body.
Not all K-Wire electropolishing is created equal! Next time you are researching electropolishing your k-wires make sure your manufacturer knows what they are doing. We have seen numerous cases of finished products getting ruined after they are finished due to a poor electropolish job.
Stainless Steel K-Wire Electropolishing
Stainless Steel Electropolishing is fairly straight forward. The majority of electropolishing is done on stainless steel products. As a medical device designer good questions to ask are:
1. How much material is going to be taken off during this process?
As electropolishing is a subtractive process, material is taken off of the surface during the manufacturing process. A good manufacturer should be able to keep material loss down to .0001 in tolerance.
2. Do you adhere to ASTM B912 – 02 standard?
The answer here should be yes and it should be on your drawing.
Nitinol K-Wire Electropolishing
As a medical device desinger, you should ask around, before excepting an electropolisher to do nitinol. I would stick with some of the larger electropolishing companies. Nitinol electropolishing is not a standard thing and some companies approach it differently in terms of the chemicals used and amplification. Different processes can lead to adverse surface finish effects. The only advice I can provide is
1. Do your homework and double check quotes and the process they are going to use before doing a large batch
2. Ask them to do a sample for you.
That is all I have for today, I hope this helps on your next k-wire electropolishing project.
K-Wire Tip Angle
The typical angle that we manufacture on a k-wire is 15 degrees. We have manufactured anywhere from 7 degrees to 45 degrees for custom parts but 15 degrees is the standard angle that we see. 15 degrees is measured against the center line of the part, not the two sides of the angle. For trocar tips, if you are looking at the face of the K-Wire, the angle is almost always 120 degrees per face or equally distributed among the three faces of the K-Wire.
K-Wire Tip Styles
The most common K-Wire tip we manufacture is the trocar tip, which is a 3 faced tip. We also manufacture diamond which is a two faced tip but this is much less common.
K-Wire Relief Angles
Some customers request relief angles but this is fairly infrequent. We can program relief angles into out machine but inspecting and analyzing them is difficult. A relief angle of 5 degrees can carry a tolerance of 3-5 degrees which essentially wipes out the relief. Long story short, we can do them, but it is very tough to inspect.
We often get inquiries for K-wires with little understanding of the options so I will try to lay out what our typical customer purchases and the cost differential between options. When someone refers to a “K-Wire” they each tend to think that there is a standard design for this type of product. My understanding is that “K-Wire” refers to a certain type of medical procedure, typically a wire used to fixate a bone fracture. So the design of a “k-wire” can vary dramatically depending on what type of procedure is being done.
The two most basic kinds of materials used in K-Wires are Stainless Steel and Nitinol. Stainless steel is the most common material used. Stainless steel tends to be more stiff while nitinol is durable. Nitinol has many additional properties of medical interest – http://en.wikipedia.org/wiki/Nickel_titanium. Nitinol typically costs about 4 times as much as stainless steel with all else equal. If you are trying to quote out a certain diameter but you are flexible, let the manufacturer know this. Often manufacturers will have stock material laying around which they can quote you a lower price for. This especially comes into play if you are doing a small prototyping run.
The most typical k-wire profile includes a trocar tip on one end, a short thread (approximately 1 cm) and a radius tip on the second end. Modern Grinding doesn’t stock K-Wires, we only make them to customer specification. In order for us to stock them we need an FDA approved design.
We have made k-wires with a double flat on the second end for drilling. We have made fully threaded k-wires. Clients have asked us for a “k-wire” with two blunt ends. I personally wouldn’t refer to that as a “k-wire” just a wire with two blunt ends.
K-Wire Electropolishing and Laser Marking
About 20% of our customers will get some sort of post process on the K-Wire. This is most commonly electropolishing and laser marking. Electropolishing is a subtractive process which brings out a chrome like shine on the Stainless Steel. Laser marking can include depth markers along the length of the wire. It can also include a unique identifier on the K-Wire.
If you don’t know what type of threads you would like, ask the manufacturer what they typically use based on the wire size you are using. If you request a specialized thread, it will end up costing you more. Threads need to be profiled into the grinding wheel or die that is being used. If you use a typical thread, the manufacturing company most likely has the tooling for the job.
There has been a flurry of activity at Modern Grinding recently with universities labs who are setting up fracture research for the semester. Many Phase I and Phase II studies are going into effect right now. We like to work with groups throughout the semester to find the right k-wires for research. Many groups will get a wire prototyping kit from us with a variety of wire types (stainless steel, nitinol) a variety of diameters and a variety of tips.
Don’t get us wrong, we feel bad for some of the animals who undergo this type of research but we are also happy that we are helping fuel innovations which help improve fracture care for future generations. Many researchers who contact us don’t quite know all of the ways we can process a wire and the lead times associated with different processes.
If you are are researching k-wire or nitinol products please contact us and we will do our best to give you the tools to succeed this semester.
Modern Grinding is a K-Wire Supplier to some of the largest medical device companies in the world. They have established themselves as a leader in the field of forming complex wire. Because they specialize in K-Wire applications, they are well suited to work on Nitinol and Stainless Steel in precise diameters.
The medical device supply chain is complex and difficult to navigate for new entrants to the field. Many companies approach Modern Grinding for customized K-Wires based on research and advanced project needs. Modern Grinding is happy to accommodate all types of projects and considers itself on the leading edge of K-Wire capabilities.
Consider Modern Grinding for your next K-Wire supply need.
K-Wire fixation is a procedure to hold bone in place for recovery after a bone fracture. Percutaneous pin fixation is the process of fixation through the skin. K-Wire fixation uses a variety of tips to help achieve percutaneous guidance to the desired location. If possible, percutaneous fixation is preferred since opening up the skin requires additional tools and recovery time by the patient.
Temporary K-Wire Fixation
In certain cases temporary fixation is all that is needed. This process can take 4-6 weeks for recovery and then the K-Wire is taken out. Sometimes the pin is left visible outside of the skin for easier removal.
Definitive K-Wire Fixation
If the fracture is small such as in hand and wrist fractures, the K-Wire maybe be place in the wrist permanently.
Lost K-Wire Fixation
Sometimes the fixation maybe back out of the bone and be lost. This is most likely if the K-Wire is between two bones which move a lot. Measures are taken to help secure the fixation such as specialized tips and threading for portions of the K-Wire.
Several articles have come out comparing varying technologies with Kirschner Wires for orthopedic procedures. The Journal of Foot and Ankle Surgery expresses the merits of this type of surgery for Proximal Interphalangeal Joint Arthrodesis – http://www.jfas.org/article/S1067-2516(13)00061-6/abstract
A similar article identifying the benefits of implants for Hammer Toe –http://www.sciencedirect.com/science/article/pii/S1067251612003055
Modern Grinding can manufacture a variety of custom surgical implants for your next research project.