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

[Juan Marti]

Hello AllTheThings..!

thanks so much for your insight. Its nice to chat to someone who 'gets'it.... I am actually a veterinary surgeon so I am doing this in dogs (pics attached of typical THR), so I appreciate the hammer comment very much

There is no way to do this pre-operation, I believe, and doing it in model plastic bones would not really achieve what I want, which is measuring the soft tissue tension across the hip. This is a combined, summated effect of things like joint capsule and all tendons and muscles across the hip.

So, I wanted to ask you about your comment about the 'fairly fast/high sample rate force gauge' and the 'high speed log of the data'. I did a 'dry run' yesterday in theatre and the event of pulling on the hohman etc until reduction is achieved will only last a few seconds, perhaps 3-5. I am trying to keep this initial experiment relatively low -cost, also bearing in mind andftrying to understand the possible limitation of going for a cheaper force gauge versus a more expensive one. I dont think I need to have the capabilities of tracking the forces to be able to graph them or anything like this and as long as I have a peak force value, i think this is all I need. So, initially, I looked at purchasing something like a Beesland SF- 500 or similar, to keep it simple and cheap. do you think this would be adequate..?? was attaching a link here but.......

I also wonder if this can be properly calibrated, though. ??

There will be NO way to standardize the angle of the instrument pulling back on the Hohman retractor, I think, since it will rely more on a 'feel' of the right direction of pull, as I am used to do it with my hand.. so this will be a limitation of the proper force aplied since the angle will probably be fairly consistent but not absolutely the same every time or 'standardizable'

I need to get you a picture of what I mean, so we can be on the same page. I also need to describe the second part of this study, which is similar. Gotta go to theater now.. Just realized, I need to have 10 messages before the system allows me to attach pics...!!

Thanks again

Juan

 

[Juan Marti]

Dear AllTheThing,

Hope you are well. I typed a reply to your last message but I am not sure what happened.....I was doing other things and perhaps I got timed out or something, since I thought I had sent it, but now can't see it on the conversation...... By the way, I am a veterinary surgeon, not a human surgeon.

No way this can be done "pre op" because, yes, the tension that we are measuring comes from the soft tissues around the hip..

I think what you mean by "fast/high sample rate"...this is to be able to detect EXACTLY the moment in which the traction acutely drops, and call that PEAK value...correct..?? . I am trying to keep this cheap and I was originally thinking of a Beesland SF 500 type of digital force gauge or similar, since I don't need to do graphs or fancy charts. But I do realise the quality of the device will be compromised in the cheaper versions....do you think something like a Beesland will be able to be calibrated and consistently measure what I need to ..?? I tried to include a link, but this system does not allow me to do this yet ( I need 10 plain messages before I can do this...)

So I think there will be no way to really standardise the angle of pulling back on the Hohman retractor, since this is more of a feel in surgery. My guess is that the angle will be roughly always the same but will not be standardised. Again, I tried to include some pics here last week, but could not.

I need to explain to you , also, the second part of this study, but I gotta go to surgery now

Juan

 

[Juan Marti]

Wel....Now that I sent you the last message, I was able to see the previous one, the one I thought had not registered.....sorry about that.... JM

 

[AllTheThings]

No problem at all

With cosine errors, you just try and be as good as you can for this application.

For sample rates, I will try and give background:

You will want to sample at about half the length of the "event". So a hand clap can be ~ 4 milliseconds. So you need to sample very 2 milliseconds, or 500 Hz. If your insertion is a half second, then you will want to sample at a quarter second of faster. This is all so you capture the peak as best as possible.

Generally, any decent force gauge can sample at 1 KHz, and return the peak. So that would be the parameter to look at when selecting a gauge.

You should be able to verify the gauge by hanging a weight off of it.

Good luck in surgery!

 

[Juan Marti]

Thanks for your response..!!

the second part of the study is to measure what is called the SCHUCK test, in humans, which is the subjective assessment of soft tissue tension across the hip by looping a long swab or tape and pulling back, in the direction of the femoral neck, to measure the resistance of the head being lifted off the socket, all the way to luxating the hip. So, this is to avoid leaving too tight or too lose a hip in surgery. Human surgeons do this routinely but I understand they never really measure the force, and this remains a subjective feel. Again, can't put a link yet so please go to Youtube and type : 'Balancing the hip and the schuck test' and you will see what I mean.

No instruments involved so the traction is more linear along the neck, and this tape could be connected directly to the hook of the force gauge, for a straightforward measurement. Still waiting for the ethical approval of this study really, so....

Thanks again

Juan