Is the Patellar Bar Dead?
Walking around the exhibit hall at a conference, I stopped at one of the booths to chat with a buddy of mine. I leaned over and said in a smug, sarcastic voice, "You're kidding me, right? These are the craziest trim lines for a BK I have ever seen; those shapes don't 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 historical literature about prosthetics, and I know that Charles Radcliffe, MS, ME, pioneered many of the concepts that are still used today in transtibial prostheses. Radcliffe's contributions are, and continue to be, extremely valuable to the prosthetics field. (Editor's note: For more information about Radcliffe, read, "Charles Radcliffe, Father of Prosthetics Biomechanics," The O&P EDGE, March 2006) I began to realize, however, that many of the theories behind the patellar tendon bearing (PTB) prosthesis were actually created in the 1950s—long before gel liners. Socket technology has not kept up with the designs and progression of new interface technology.
At the end of 2008, I needed a few extra continuing education credits, so I decided to take one of the inaugural RCR socket design courses at Northwestern University Prosthetics-Orthotics Center (NUPOC), Chicago, Illinois, organized by the Orthotic and Prosthetic Group of American (OPGA), Waterloo, Iowa. Two days before I left for Chicago, OPGA called and said 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 to say, "No," but I realized that the worst that could happen was that I would fail miserably, so I took the spot and haven't looked back since.
Dale Perkins, CPO, with Rehab Systems Orthotic and Prosthetic Technologies, Boise, Idaho, challenged my conventional thinking as well as my historical perspective about transtibial socket design with the development of the RCR socket. The socket design is a result of challenges he experienced with putting a patellar bar in his own prosthetic socket. Perkins underwent a closed femoral shortening on his limb to even his knee center and to get a better foot under his socket. One of the unintended consequences of the femoral shortening was that his 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, which 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 mid-stance, his gait pattern improved.
Perkins concluded that with the advent of liners, he no longer needed to load the patellar tendon. In fact, by relieving the patellar tendon, he found that it is able to fully fire. Relieving the tendon allowed the quadriceps to better respond to strength training, and he was able to achieve a more normal extension at mid-stance.
I, and 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 newfound knowledge, I went back to my office and tried it on my first, brave patient volunteer. The patient was in a socket with a very tight anterior-posterior (AP) dimension socket—so tight, that it actually caused a bulge in the popliteal area. My patient told me that he mostly just sat around because it was too painful to walk any distance. I cast 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, he began to smile; this was the first time he was truly comfortable. I knew at that point not to do too much to the cast because I didn't want to 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 I was confident that I had provided a great-fitting socket.
The patient returned after three days, and I was able to quickly align the prosthesis and allow him to leave on the copolymer check socket. I followed up with the patient after one week, and he had increased his activity level and kept telling me he was amazed not to have pain. After this experience with the RCR, I wanted all of my transtibial patients to experience the comfort and freedom it offers.
I recently documented a case in which a patient had worn out his Össur Comfort 3mm locking liner in the patellar tendon area and had developed a dark calloused spot on his patellar tendon. I put him into an RCR socket, and over the course of four weeks, the callous lightened and eventually returned to normal, supple, non-calloused skin. The patient's gait pattern improved and became more normal, and he felt uninhibited around his knee because there was no material hindering full extension. The cosmesis was also improved because the lower-profile socket had no anterior gapping. He was thrilled 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-foot 4-inch frame out of a low chair.
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 mid-stance. I have also discovered that the problems I was having with distal tibia breakdown and alignment issues have been resolved with the RCR method. Patients love the extra extension and flexion. I was further surprised that even the relatively happy patients I already had became even happier when I switched them to the RCR because of the increased freedom they felt. Physical therapists have told me that they are impressed with the design. They also tell me they never really understood why there was a bar in the socket to begin with.
I believe that the RCR socket design and theory can benefit all transtibial amputees. It is strange to think about not having a bar in a socket, but the time has come to say goodbye to the tradition and keep on developing socket designs that are relevant to today's advances in interface technology. The RCR design and process is systematic and gives me confidence that I can make patients happy and comfortable in their prostheses.
Brent Wright, CP, BOCO, works at EastPoint Prosthetics and Orthotics, Kingston, North Carolina. He maintains a blog called "LifEnabled" at http://livinglifenabled.com and can be reached at