making guides

[rpapandrea]

I have been printing bones for surgical planning for over 5 years.  I will sometimes invert a contralateral to create a "normal" template.  My next step is to create custom cutting or drilling jigs.  Does anyone have any experience with this?  Any suggestions for software?

 

Thanks,

 

Rick Papandrea, MD

Partner, Orthopaedic associates of WI

2014.forearm.pdf

[mikefazz]

While I haven't done this before from similar projects I can think of a fairly simple procedure:

1.  Create 3D model of anatomy to do surgery on

2.  Create cylinders to represent drill bits and place/orient them where you want

3.  Create a block that will represent the jig and orient it so it overlaps the anatomy

4. Do boolean subtractions to remove the cylinders (create holes) and intersecting anatomy (create reference surface)

 

Mike

 

 

[Dr. Mike]

Custom cutting and drilling guides for intra-op use are a specialized medical product and thus extra care needs to be taken. I am a big advocate of open source and free software, but in this case I think you should use FDA approved software such as Mimics from Materialise.  Unfortunately, it is pricy. Alternatively, you can contact a company that designs custom surgical guides and is aware of the evolving FDA guidance with respect to 3D printed medical devices. The image below is a pic I took at RSNA 2016 of a fibular cutting guide that was used in a mandibular reconstruction. It was made by the 3D systems subsidiary Medical Modeling.

 

Hope this helps.

 

[ztan]

At the moment, FDA required materials are required for jig usage in practice in the US.  The cost is significant, but this is built from time saving for surgeons ($$$), FDA compliance ($$$$) and medicolegal risk ($$$$$).

 

I have my reservations about a lot of the currently available custom jigs which often require much more extensive exposure and periosteal/tendon stripping than you would normally do, as the surface registration occurs at the bone surface rather than over periosteum and tendon insertions.  I prefer making a few models and doing surgery in plasticus for planning and plate pre-contouring than using jigs.

 

Having said that you can either:

Free: Learn how to use Blender to intersect a part of a bone with a guide/stamp of your creation.

$$$: Learn how to use SolidWorks.

 

Basic steps:

1. Have models of intact anatomy and corrected anatomy - this requires learning how to perform digital surgery using your software program.

2. Create a guide tool geometry.

3. Intersect with the surface you want to have surface registration with.

4. Decide on cutting planes/screw trajectories - you will need geometry and/or models of the implants you want to use.

5. Intersect these with the guide and build suitable guide structures based on what you want to put through.

 

I would suggest that if we want to make a collaborative guide on how to make guides, we do this using Blender to get maximum accessibility.

[kopachini]

Regarding to this cutting jigs, what plastic are they made from? And what type of sterilisation is used? EtO?

[Dr. Mike]

I just returned from a 3D printing conference and Mayo Clinic is using the Form 2 printer with their dental resin to make cutting guides for complex craniofacial surgery. You can learn more about the Dental SG resin here. 

[mikefazz]

I've looked a little into FDA approved materials and am interested in what it takes for a material to be considered safe for surgical guides.  The dental material above adheres to the following:

EN-ISO 10993-1:2009/AC:2010, EN-ISO 20795-1:2013, EN-ISO 7405:2009/A1:2013

 

The material guidel!ne from taulman3d (http://taulman3d.com/guidelne-spec.html) meets:

ISO 11607-1: 2006, ISO 10993, USP Class VI, USP <661>, DMF (Drug Master File) number  16525

 

Taulman3d also has nylon 680 (http://taulman3d.com/nylon-680-spec.html)

CAS Reg. No. 51995-62-1 

meets:  21CFR177.1500 / CFR177.1395

testing follows  regulations 21 CFR Parts 210, 211 and 820

 

Now I realize just because the material is approved doesn't mean it is approved after printed as it has to 'go through' the machine so that may require a COA.

 

Of course any advice here is not taken as 'legal advice' just interested in what it takes to be able to properly produce surgical guides.  From my understanding it is mostly a requirement of the client to get FDA approval, I would expect a surgical guide to be at least class 2 and likely class 3.

[kopachini]

Thanks for your replies dr. Mike and Mikefazz

[Dr. Mike]

This is an area of active debate and discussion. The FDA is evaluating the situation and still working on recommendations and guidelines for surgical guides. Nobody knows what the regs should be, including the FDA. Its hard to keep on top of the latest recommendations since they are constantly changing. Here is an article written by the FDA workgroup on 3D printing. Here is a link to the FDA page on the topic. Hope this helps.

 

[mplishka]

Just some thoughts on this topic:

 

The FDA is of the mindset that  3D printed devices  are pretty much equivalent to their non-3d printed counterparts unless there are new concerns introduced by the printing process with regards to safety  or efficacy .   It is the responsibility of the manufacturer to prove that there are no new concerns, or, at least establish there are no new concerns.

 

Surgical inserts and other manual surgical tools, in general, are class 1 devices. Class 2 devices are those that are doing something else (think interventional devices, etc.) and not just going along for the ride so to speak.  Class 3 devices are directly intervening in the well-being of the patient, and they're typically implanted in the body and left forever. There are exceptions to these, as sutures and various spine implants, for example, are Class 2, but that is because at the end of the day it's all about risk. So, well established technologies that carry a low risk to the patient, even though they may be implanted, are often Class 2. The FDA is constantly revisiting the classifications of devices as their histories become more in depth.

 

Regarding materials, again, it's based on risk. Once a material has a track record of being safe for a particular use, it's safe. That is, unless the material itself is somehow modified by a non-typical process. In 3D printing, the process and material are very intimately entwined. In other words, it's hard to make a functional product unless the processing parameters are pretty spot-on. So then it comes down to what is being done to the material afterwards. The best way to find out is just to take  some material processed like the finished product (from manufacturing all the way through to sterilization) and do your testing. You can be confident then that, barring material formulation or process changes, the material will be fine.

Although the FDA doesn't like using the term, if you do an internet search for class 6 materials, it'll give you a good idea of how  materials are tested for various types of use. I personally still like using this as a benchmark just because it's easier to access them to jump into the ISO regs.

There's also cleanliness and sterility not to mention pyrogenicity,( but I just did :-) ).  Again, it's just a matter of processing a device a certain way, sticking to that process, and testing a representative sample.

I hope this makes sense. If it doesn't please let me know.

 

[Dr. Mike]

Here is a freeware tutorial I wrote for a presentation at RSNA. In it, I discuss the latest information from the FDA on when it is OK to use non-FDA reviewed software.