My thanks to all that took the time to respond. I have quoted most of the responses below. Sorry if you are embarrassed by the spelling and typographical errors, but using spell- check doesn’t take all that much longer (I’ve really put myself on the line here, haven’t I?). One respondent requested that his response not be posted, some were personal messages (much
appreciated) and not really pertinent to the topic. All these were not quoted. At least one writer generously offered to respond to specific questions I might have, and in the interest of his time and sanity I have declined to include contact information.
Reviewing the material leads to the conclusion that most of the respondents
(10) do not use the technique. One is vehemently negative about it and nine are aware of the Otto Bock/TEC and Ossurr methods. Interestingly enough four of the responses cited the Ossurr method, which I would characterize as employing positive pressure in a sealed chamber and not negative, vacuum, pressure. This despite the fact that I specifically referenced the use of vacuum. Only one individual pointed out the discrepancy in his response, while the others did not. Six responses were positive about the use of vacuum assist. At least two of the respondents seemed to use it sparingly, while the others seemed to use it more routinely. At least one was quite enthusiastic.
As at least one individual pointed out, correctly, that there is nothing new about the use of assistive methods in casting TT residual limbs. Drew Hittenberger published an article in the 70’s describing his method. USMC carried the necessary parts in their catalog for years. It never seems to have caught on though. As I recall Drew specifically described the ability to hand mold and shape the tissues while under vacuum as an advantage. A variety of other techniques describing displacement media, fluidized sand beds, dilantancy (dilantency?), etc have been since at least the 50’s.
Again, they never seem to have had much impact, but variants emerge from time to time. Fads come and go. The use to CAD-CAM does seem to be catching on as the systems get more sophisticated.
I brought the subject up because one of my BK’s asked me about it. I would describe him as an active ,vigorous walker, moderately difficult to fit, and a good reporter about what he is experiencing. He stated that one of the best sockets he had ever had had been supplied by Jon Stakosa employing vacuum assisted casting. Knowing Jon’s reputation I suspect the results owed more to the technician that the technique. In any event, thanks again to all.
The responses follow.
Charles H. Pritham, CPO, FAAOP
cpritham@ec.rr.com
1. As part of the VASS/ Harmony system now taught by Ottobock, a cast is taken using a vacuum pump with an air bladder over a plaster wrap cast and gel liner. The vacuum method is a nice way to obtain a TSB cast and it will hold any modifications you mold in without having to hold your hands in a certain position until the plaster sets off
2. Iceross (ossur) makes the IceCast system
3. This can be tricky casting technique if you get a little carreid away witht he vacuum.I Take an old iceross clearpro liner and thread a male gas inlet into the pin threads.Then I push a hole into the liner through the area formally the site of the pin attachment.Take a band of used alpha liner and reflect it onto the thigh area.This will maintaina airtight seal with the liner.Hook up a hand powered pump(like the ones form a auto store for bleading brake lines) and apply vacuum until you reach your desired psi.This is a cost effect way of doing this as all of the components are old ,slightly retired components that cannot be used for anything but the trash can.I prefer this method on boney promient residuals and atheletes.Flabby tissue will just creat too much confusion and improper fit.Hope this helps
4. You may want to contact Otto Bock about TEC’s casting method using vacuum.
5. Me too!!!
6. I have done this periodically over the years and I do it by casting with relatively cold water and one layer of flex plaster and one of rigid. Then I pull a cast sock over the cast and then a plastic bag. Then I put the small latex hose from my vacum system into the bag, under the cast sock and fold the plastic bag around the thigh and seal the suction hose. I only eyeball the amount of sucktion because I don’t have any guages, but I get a pretty tight cast and use it when I have trouble getting a really nice tight fit proximally around the flairs. I don’t use it as much anymore when I cast with silicone liners. I did it last week for an old BK that I wanted to do a hard socket on. He doesn’t like it tight distally but wants it really tight proximally.
7. Contact Ossur. They have had a vacuum casting system for years. I think they are on their 3rd or4th generation of systems. I’m sure they would be happy to answer any questions you might have
8. have only seen this technique used for tec liners….maybe tehy could help give you some training.or even souorce a system which will work. I believe they might be owneed by Otto Bock now.
9. The otto bock rep was just in last week and handed me a sheet about this technique. It is not a new thing, TEC was teaching this at least 6 years ago (my prosthetist used that technique on me, and I had one very uncomfortable socket from him). I don’t use that at all, it does not seem to work. I have done it to myself a few times, just seeing what tricks in the modification steps would work with a cast like this, which would make a good fitting socket. I finally got tired of wasting my time and plaster. A good hand cast works better still.The vacuum cast is a poor attempt to be lazy and take the easy way out. Slap on the plaster, put on a bag, hook up a vacuum tube and wait 6 minutes for it to set up. Very clean and lazy.
And the results are poor.Just my experience, and my thoughts.
10. Ossur has had a system around for years.
11. don’t know if this falls into the category you describe, but I’ve used the Ossur Ice-Cast system over liners with pretty consistent success. I like the fact that you can vary the pressure dependent on the shape/consistancy of the residuum
12. TEC / Otto Bock has a video, I believe called “vacuum casting”
techniques. It’s obviously geared toward their specific liner, but the fundamentals are about the same. Otto Bock sells the three latex casting sleeves shown in the video for I’m sure is under a C note (which is so much nicer then a trash bag). You can purchase a needle valve, the flexible PVC hose at a hardware store as well as the plumbing fittings to use any old vacuum pump to cast with. The needle valve allows you to regulate the amount of vacuum drawn on the cast. I believe that vacuum casting is recommended for global loading recommended for thick gel liners. There is an added benefit of casting under vacuum, the plaster sets off much quicker.
13. I have settled on this casting technique after trying many other methods; (including using TracerCad with the tracing pen and the Omega T Ring system w/ the 8 small digital cameras)….Apply a knee-hi nylon stocking directly onto the RL, or over a properly sized gel suction liner, coming from proximal, situate the hose from a vacuum source (25-30lbs) just proximal to your anticipated trimline underneath the nylon making sure you cover the hose end w/ a piece of stockinette, (I usually tape the hose to the thigh), then apply a small, clear, very thin plastic bag (I use very small wastepaper basket bags) over everything making sure that the bag seals on the mid-thigh and tape off (I use 3M Transpore, great tape for many uses). There may be slight leakage where the bag goes over the hose…..I usually ask the patient/client to place two fingers on either side of the hose w/ gentle pressure to complete the seal and that usually works fine.
Sometimes w/ a little moisture or water, the bag seals itself around the hose. What you get from this is a very accurate picture of the underlying structures (even with a gel liner) and the tissue is already somewhat pre-tensioned. Next, I apply tubegauz doubled and also taped off. Mark out your favorite landmarks as needed. Flex knee to about 80 deg and use a 4 layer plaster splint to capture anterior aspect and rollout of femoral condyles and anterior tibia, when rigid, return knee to slight flexion (about 10 deg) and circumferentially use orthoflex or similar to capture volume. Finish off w/ the rest of the rigid roll. I continually check the
vacuum gauge to be certain it is still pulling 25-30. Now, if I’m doing a
weight-specific socket, I’ll modify by hand; but if it is a total surface bearing design with a gel liner, all I have to do is use the TracerCad wand and digitize to capture shape and volume, reduce anywhere from 2%-4% circumferentially, and I consistently get a socket w/ a sheath fit over the gel liner
