Category Archives: Prosthetic Technical Tips

Why is the Rush Foot so Popular?

I was having a conversation with a friendand fellow prosthetist.  We were discussing which feet we used and he said that at the last Amputee Coalition of America conference the Rush Foot seem to be the foot of choice. He seemed a little perplexed because he had never used one before. I told him if he used one he probably would not order anything else.
I have been using the  Rush Foot for as long as they have been around. I continue to use it because patients love it. The walking is smooth, uneven terrain is not an issue, hills and ramps are no problem. The only issue I have had is one foot started to make a clicking sound and I could not trace it down. The clicking sound ended up being the foot starting to delaminate. When I started speaking with the people at Rush I realized I had gone too soft on a patient  who was a super high activity patient. The foot was essentially two categories less than what he needed. They replaced the foot under warranty without a hesitation. Great customer service! Great foot! Order one! Your patients will thank you.

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Hack for lateral wall of Transfermoral Cast before pouring plaster

Instead of pulling out the draw knife, pre-modify your cast by making two slits diagonally towards the trochanter.  Fold in the lateral aspect of cast and use tape or a staple to hold it in place.

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Is the Patellar Bar Dead?: Review of the RCR (Now StabileFlex) below-the knee prosthetic socket from Coyote Design (Part 5)

Using the RCR method over the last few years has been a rewarding road of discovery. I have a better understanding of gait and normal anatomy. I have learned that the high tension cast in full extension gives me the best “snapshot” of the limb for comfort at midstance. I have also discovered that the problems I was having (distal tibia break down and alignment issues) have been cured with the RCR method. Patients love extra extension as well as flexion. I was surprised that even the relatively happy patients I already had were even happier when I switched them over to the RCR because of the increased freedom they felt. Lastly, I have been overwhelmed with the feedback from physical therapists saying that they are so impressed with the thoughtfulness of the design, and tell me they really never understood why there was a bar in the socket to begin with.

I believe that the RCR socket design and theory benefit ALL below-the-knee amputees. It is strange to think about not having a bar in a socket, but the time has come to say so long to the tradition and keep on developing socket designs that are relevant to the interface technology advances we now know. The RCR design and process is a systematic process which gives me confidence that I can make patients happy and comfortable in their prosthesis.

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Is the Patellar Bar Dead?: Review of the RCR (Now Stabileflex) below-the knee prosthetic socket from Coyote Design (Part 4)

I recently documented a case where a patient had worn out his Ossur Comfort 3mm locking liner in the patellar tendon area. He also had a dark calloused spot on his patellar tendon. I put him into an RCR socket and the patient was thrilled. Over the course of 4 weeks, the dark callous turned lighter and eventually to normal, supple, non-calloused skin. His gait pattern was more normal, and he felt uninhibited around his knee because there was no material hindering full extension. The cosmesis was better because the socket was lower profile with no anterior gapping. Lastly, he was ecstatic that he was able to bend his leg up to about 110 degrees under him, which made it easier for him to get his 6’4” frame out of a low chair.

Initial evaluation

Two weeks after initial fitting

4 Weeks After Fitting

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Is the Patellar Bar Dead?: Review of the RCR (Now StabileFlex) below-the knee prosthetic socket from Coyote Design (Part 3)

Dale’s conclusion is that with the advent of liners, I no longer need to load the patellar tendon. In fact, if I relieve the patellar tendon it is able to fully fire. Once I relieve the tendon, the quadriceps are allowed to gain strength and more normal extension is achieved at midstance. With these concepts, I, along with others, have hypothesized that this may be the missing link to a normal gait pattern rather than a “normal amputee gait pattern”.

Armed with my new-found knowledge, I went back at my office and tried it on my first, brave patient volunteer. The patient was in a socket with a very tight AP─so tight, that it actually caused a bulge in the popliteal area. He said he mostly just sat around because it was too painful to walk any distance. I casted him with the two-part high tension cast that the RCR mandates and had him weight bear through the cast. As he was putting weight through the cast, a smile crossed his face; this was the first time he was truly comfortable. I knew at that point not to do too much to the cast because I could mess up the fit. I followed the modifying instructions and enhanced my cast accordingly. The process did not take a great amount of time, and it gave me the confidence that I had a great fitting socket. The patient returned, and I was able to quickly align the prosthesis and allow the patient to leave on the copolymer check socket. I followed up with the patient in one week, and he had increased his activity level and kept telling me he was so amazed to not have pain. After this experience with the RCR, I knew that all my transtibial patients deserved to experience the comfort and freedom it offers.

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Is the Patellar Bar Dead?: Review of the RCR (Now StabileFlex) below-the knee prosthetic socket from Coyote Design (Part 2)

At the end of 2008, I needed a few extra continuing ed credits, so I decided to take one of the inaugural RCR courses at Northwestern University organized by OPGA. Two days before I left for Chicago, OPGA called to let me know that one of their “hands on participants” had cancelled, and they were looking for a volunteer to take the spot. I must admit, my first thought was “no,” but I realized that the worst that could happen was to fail miserably so I took the spot and have not looked back since.

Dale Perkins, CPO with Rehab Systems in Boise, ID challenged my conventional thinking as well as historical perspective of transtibial socket design with the development of the RCR socket. The socket design is a result of challenges he experienced by putting a patellar bar in his own prosthetic socket. Dale underwent a closed femoral shortening on his limb to even his knee center, as well as to get a better foot under his socket. One of the unintended consequences of the femoral shortening was that the quadriceps were now long, which meant he had to undergo quadriceps strengthening. He had no issues in his socket at the time of the surgery, however, as he gained strength, he realized his patellar tendon was starting to bother him. He evaluated his socket and decided to remove the bar and essentially relieved the tendon. He found that once the tendon was relieved, he was able to continue strengthening his quadriceps. He also found that he was getting more extension than he had previously achieved with the bar. With the added normal extension moment he was getting at midstance, his gait pattern improved as well.

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Is the Patellar Bar Dead?: Review of the RCR (Now StabileFlex) below-the knee prosthetic socket from Coyote Design (Part 1)

As a young, know-it-all prosthetist, I leaned over to my buddy and said in a sarcastic smug voice, “You’re kidding me right? These are the craziest trimlines for a BK I have ever seen; those shapes do not make any sense and would never work.” Over the next two years, however, I could not get my mind off of what I had seen, and I wanted to know more.

I enjoy reading a great deal of prosthetic historical literature, and I know that Charles Radcliffe, MS, ME pioneered many of the concepts that are still used today in below-the-knee prosthetics. His contributions are and continue to be extremely valuable to the field of prosthetics. I began to realize, however, that many of the theories behind the Patellar Tendon Bearing (PTB) prosthesis were actually created in the 1950’s─long before gel liners. Socket technology has not kept up with the designs and progression of new interface technology

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Neat little trick to hold rivet punches




I learned this trick from Frank Hodges at Sunstone Lab.  Use an inexpensive magnetic tray from Harbor Freight and stick it right on your vice.  The rivets punches are now easily accessible and always in one place.


Magnet Rivet Holder

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Guest Post: Jeff Boonstra, CP, How to make those spectra socks last longer on a carbon fiber prosthetic foot. Use Shearban on the “toe”

Here is a tip that I thought was very cool.

Jeff Boonstra, CP, of Advanced Prosthetics Center emailed me this tip. Cover the toe of your carbon feet with a piece of shearban. This will increase the length of the spectra socks on the high activity feet by at least 2 times.

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Tired of feeling like a porcupine hugged you after grinding on carbon…check out new composite from Coyote Design…NO ITCH!

Tired of feeling like you have a porcupine in your shirt after grinding a carbon fiber prosthesis? Coyote Design has a new composite out that does not itch… and is flexible.

The RCR socket design from Coyote has always been most successful and most comfortable when the socket was flexible. In my experience I have had a patient love their copolymer test socket but not like their definitive carbon socket. The most common response when I make the switch back into a copoly socket is that it feels like it moves with them and is softer.

A complementary resin/composite combination has been the key to a flexible socket. Unlike other composites on the market the Coyote Composite is actually the simplest to work with. The lay-up for a normal below the knee socket with the Coyote Lock is two layers of multi-size nylon, 2 layers of composite, and two layers of multi-size nylon (reinforce distal end as needed). The composite will take pigment extremely well, and no extra nylons are needed to hide composite. When you grind the socket it does not itch and it finishes beautifully. So far my patients have loved the sockets.

If you want more information you can visit . If you want a couple insider tips on the resin and promoter we use, shoot me an email and I will let you in on a couple secrets.


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