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Richard Erlacher
09/12/12 09:57
Read: 659 times
Denver, Co
USA


 
#188312 - I'm not sure ...
Responding to: Erik Malund's previous message
It all depends on whether what's needed is a quantitative assessment of backpressure, or just a qualitative one.

I've seen a number of ways in which below-knee prostheses are fitted, as that's what I have worn for the past 40 years, but it's always in the realm of "art/black-magic" as far as I can tell, as the experience and skill of the prosthetist is a major factor in the outcome. I've discussed this with one or two of these guys, and they seem to feel it's really important to know where the hard regions are, and where the transition regions are, and even which areas are predominantly soft and therefore moveable tissue. That soft tissue, BTW, often contains water which, when the device is worn, can be worked out, thereby affecting the security of the fit. That fit affects the precision with which one can control and rely on the footfall while walking. As the fluid in the stump is reduced by activity, the fit suffers, unless there's really good registration between the socket and the hard portions of the stump.

After several decades, the hard areas on my own stump are just skin covering bone. Shortly after amputation, that's not the case, though some prominent hard areas are already well defined. As the amputee ages post-op, the muscle can atrophy, becoming reduced in volume and more "flabby", making its location critical as opposed to those hard areas, as excessive movement can easily cause blistering.

I'm not sure how much useful information can be extracted from MRI or ultrasound records, particularly in view of the fact that incremental swelling occurs, at least in my case, as soon as the prosthesis is removed. This increases as time passes. I know it sometimes helps with fit if the amputee wraps the stump in an "ACE" bandage as the fit procedure progresses. Investigation of what quantitative information and qualitative information can be extracted from those examinations, but I do wonder how the data can be interpreted without involving specialized medical personnel.

Cost is a factor, after all, as some of us pay for some of our own prosthetic work.

I'm still aghast at the amount the MRI costs here in the U.S. That's probably not because of the hardware, but because of the specialized personnel required to interpret the resulting images.

RE


List of 49 messages in thread
TopicAuthorDate
How would you do this?      Richard Erlacher      09/10/12 10:30      
   I have no idea if this would work, but ....      Erik Malund      09/10/12 10:32      
      How would one actuate them?      Richard Erlacher      09/10/12 12:29      
   strain guage      Mahmood Elnasser      09/10/12 11:03      
      Yes, you might be onto something.      Richard Erlacher      09/10/12 12:49      
         Computer-controlled?      Per Westermark      09/10/12 16:37      
            computer controlled      Richard Erlacher      09/10/12 19:52      
               Calibration + redundant force-limitation      Per Westermark      09/11/12 00:03      
               Interesting problem      Jim Granville      09/13/12 15:06      
                  Yes, it seemed coarse, at first.      Richard Erlacher      09/13/12 17:08      
                     Precision is cheap ?      Jim Granville      09/14/12 15:15      
                        I don't follow ...       Richard Erlacher      09/15/12 09:59      
                           Precision      Jim Granville      09/15/12 19:09      
                              other considerations      Richard Erlacher      09/15/12 20:15      
         Tomographic imaging?      Christoph Franck      09/11/12 04:47      
            There's one major problem ... maybe two ...      Richard Erlacher      09/11/12 09:20      
               $100 MRI unit      Erik Malund      09/11/12 09:31      
                  I'm not sure ...       Richard Erlacher      09/12/12 09:57      
         Voice coil and LVDT?      Oliver Sedlacek      09/12/12 02:37      
            Not having a lot of experience with this sort of stuff ...      Richard Erlacher      09/12/12 10:07      
               Danger/problems with hydraulic since no spring effect      Per Westermark      09/12/12 13:55      
                  A few things puzzle me with this approach      Richard Erlacher      09/13/12 02:07      
   Ultra Sound Probing      Michael Karas      09/10/12 16:36      
      Ultra-sound is better for measuring surface or sub-surface      Per Westermark      09/10/12 16:39      
   I would not use volumetric imaging      Justin Fontes      09/13/12 11:05      
      I'm not sure what you mean      Richard Erlacher      09/13/12 16:59      
         another thought      Rick Gebhardt      09/17/12 13:43      
            I consider that one of the more "pregnant" approaches      Richard Erlacher      09/17/12 15:25      
               Lots of options available      Per Westermark      09/17/12 16:14      
                  You've got to consider cost      Richard Erlacher      09/18/12 16:50      
                     Cost/safety      Per Westermark      09/18/12 18:29      
                     Cost target?      Oliver Sedlacek      09/21/12 08:37      
                        The price target comes from a few prosthetists      Richard Erlacher      09/21/12 21:46      
   comercial CMM      Mahmood Elnasser      09/17/12 13:58      
      This only received cursory examination       Richard Erlacher      09/17/12 15:28      
         pneumatic actuator      Rick Gebhardt      09/17/12 20:14      
            Yes ... but what would this cost?      Richard Erlacher      09/17/12 23:30      
               100 rods?      Per Westermark      09/18/12 02:04      
                  Patient size ...      Christoph Franck      09/18/12 06:12      
                     That's what I'm considering      Richard Erlacher      09/18/12 07:50      
                     AAACK! ... another double post ...       Richard Erlacher      09/18/12 07:50      
                  it's not as big as you think!      Richard Erlacher      09/18/12 07:40      
                     90% coverage      Maarten Brock      09/19/12 03:47      
                        So maybe vacuum pump for the too fat people      Per Westermark      09/19/12 06:38      
   I do not know if this is relevant, but      Erik Malund      09/19/12 07:52      
      I'll have to look into this.      Richard Erlacher      09/19/12 09:13      
         Single air pressure sensor sensor for tip force guestimate      Per Westermark      09/19/12 11:27      
   What about infrared?      Marshall Brown      09/21/12 03:03      
      How would you do this so it would retail for under $5k      Richard Erlacher      09/21/12 08:21      

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