Gas Sterilization of a Force gauge, to be used in orthopedic surgery..??

[Juan Marti]

Good morning friends,

I am interested in taking a hand-held, digital force gauge (dynamometer) into surgery to measure certain forces, during hip replacement surgery. My concern is, of course, to have this device sterile and safe for my patients. Normal autoclave sterilisation will not be possible but I was wondering of Ethylene Oxide would be Ok for a device like this, because I have read about EO and problems with batteries, for example. The device I am thinking of may have embedded batteries that would connect to a charger OR normal AAA batteries..... so if having embedded problems is an issue with the integrity of the electronics ( or even a safety issue due to flammable gas....). could I gas sterile the device without the normal AAA batteries, gas-sterilize these separately and assembly everything in surgery..?? We routinely EO everything that cannot be autoclaved, of course, including electronics and cameras inside endoscopes etc.

This is my first post so the system does not allow me to insert a link. The typical force gauge, the kind I am thinking of is something like a BEESLAND SF-500 Force gauge or similar, if you want to have a quick look online

I would greatly appreciate your expertise or your suggestions to other forums that may be more appropriate for the question.

best wishes

Juan

 

[planB]

Juan,

battery-containing devices may _only_ be EO sterilised if the energy-source is designed to be physically isolated from igniting the sterilant in the chamber. Thus, EO-sterilizing the typical force gauge with batteries and typical household AAA batteries could lead to a similar disastrous outcome as depicted here.

Would wrapping the device (as typically done in robotics-assisted surgery) and only sterilise the patient-contacting components be an option?

HTH,

 

[Juan Marti]

Dear HTH,

Thanks so much for your reply. I take it that even sterilizing normal AAA batteries by themselves, separate from the device, could result in an ignition....

SO, :1. Is there another way to get these batteries sterilized..??.
2. Do you know if the EO sterilizacion process would damage the electronics of the force gauge..??

IF the batteries COULD be sterilized in another way, AND the device worked after EO sterilization, I could assemble the sterile components in surgery....If not, wrapping the non- sterile device as you describe may be the only other option , but would not be my preffered option, for sure.

Juan

 

[planB]

ad 1: the first 10 hits of this Google query provide you with some option to scope this topic. Note that these references typically talk about designated medical-device batteries and not household batteries.

ad 2: typically, EO is the preferred sterilization method for devices containing electronics (and withstanding pressure changes).

Hope this helps,

 

[Juan Marti]

Thanks Plan B,

yes, I had done that Google search before coming in here. As you say, I could not find any information about sterilising household batteries.

Do you suggest any of the other forums in here for this specific question of sterilisation of household batteries..?

Also, can you direct me somewhere where I can ask more detailed questions regarding the working modes of these force gauges, such as calibrate, peak mode measurements etc.??

Thanks again

Juan

 

[AllTheThings]

A digital force gauge will have a host of things in it that may get damaged by an EO process: conformal coatings on the PCB, whatever adhesive is used to bond strain gauges to the load cell...Silk screening on the control buttons are also a risk. I would avoid doing that if at all possible.

I would STRONGLY recommend sterile bagging with your end effector exposed, then sterilizing the end effector only...Or keeping the whole thing bagged, even the end effector, if you can. There are some products that may suite your needs: Protek™ PullUp™ Instrument Cover for Vacuum Assisted Biopsy Systems – Aspen Surgical

 

[Juan Marti]

Dear AllTheThings,

thanks so much for this information.

Juan

 

[AllTheThings]

Dear AllTheThings,

thanks so much for this information.

Juan

Any time! I may be able to answer your force gauge questions as well. I do a fair amount of force measurements.

 

[Juan Marti]

Dear AllTheThings

I will try to explain what I am trying to do. I would like to measure the force needed to reduce a hip during a hip replacement surgery. So, basically, the THR surgery is composed of replacing your socket with an artificial cup, your ball (femoral head) with a stem/neck, to which a metal ball is applied. Finally, the ball is 'popped' into the socket, to reduce the hip. The final tension across the hip can be increased by the surgeon, by applying sequentially longer neck/head combinations, so to avoid a hip that is left too loose in surgery. I want to measure the traction force applied to an instrument, which 'drives' the femur to pop the head into the socket. Typically, of course, it is the surgeon's hand who pulls back on this instrument (called Hohman retractor) until he head goes in so my idea is to connect the force gauge to the retractor and pull the force gauge back manually. Hope this makes sense....

So what I envision is that as I start to pull on the force gauge, the load goes up until the moment when the hip is reduced, when the load abruptly decreases. Would the device record the highest force achieved, before it acutely drops..?? Is this what is called the peak value..?? If not, I would have to look at the screen constantly and see how high the number goes, before it drops..!!

Thanks

JM

 

[AllTheThings]

Dear AllTheThings

I will try to explain what I am trying to do. I would like to measure the force needed to reduce a hip during a hip replacement surgery. So, basically, the THR surgery is composed of replacing your socket with an artificial cup, your ball (femoral head) with a stem/neck, to which a metal ball is applied. Finally, the ball is 'popped' into the socket, to reduce the hip. The final tension across the hip can be increased by the surgeon, by applying sequentially longer neck/head combinations, so to avoid a hip that is left too loose in surgery. I want to measure the traction force applied to an instrument, which 'drives' the femur to pop the head into the socket. Typically, of course, it is the surgeon's hand who pulls back on this instrument (called Hohman retractor) until he head goes in so my idea is to connect the force gauge to the retractor and pull the force gauge back manually. Hope this makes sense....

So what I envision is that as I start to pull on the force gauge, the load goes up until the moment when the hip is reduced, when the load abruptly decreases. Would the device record the highest force achieved, before it acutely drops..?? Is this what is called the peak value..?? If not, I would have to look at the screen constantly and see how high the number goes, before it drops..!!

Thanks

JM

That sounds like a really interesting project, and it makes sense. I wonder if that could be done pre-operation, with just the machined ball and socket? Or are there also forces from soft tissue that affect the force of insertion?

It seems like you would want to set up the force gauge to measure peak force...Which means you need a fairly fast/high sample rate force gauge. Chatillon, Imada, Mecmesin, and others all make decent gauges that would fit the need. They all make gauges that can record minimum or maximum force, so you can capture that peak. That will be accurate, second only to having a high speed log of the data. All of them will also have adapters that would allow you to hook onto the instrument. After that, it just becomes math: The lever arm of the Hohmann retractor, etc.

I am guessing that the biggest challenge would be convincing the surgeon to do it. In my (very limited) experience, most don't like anything between the 'feel' of the instrument and their hands. But maybe ortho is different. They use hammers

The second biggest challenge would probably be maintaining a 'normal' force, where the force gauge is pulling perpendicular to the lever arm of the Hohmann retractor. If not, you get error with respect to the cosine of the angle.

Hope this helps. You are working in a really neat realm