Trans-USA Hip Disarticulation/Transpelvic Prostheses Tour: Part Five = Torrence, CA
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February's Corner [ February ], highlighted our visit to Ventura, California and the David Littig's demonstration of how he applies the Strut he invented. The next day, Steve Taylor and I traveled from our hotel to nearby Torrence and visited Carlos Sambrano at his facility, Life-Like Prosthetics. As the name suggests, Carlos' philosophy emphasizes creating a prosthesis with as natural an appearance as is feasible. He uses proprietary polyurethane elastomers to create both flexible sockets as well as durable and stain-resistance coatings over the protective foam covering of the prosthesis.
Carlos' technical skills are outstanding, and he devotes a great deal of time and effort to making prostheses that are both functional and aesthetic. Since people with these high-level amputations have lost such a substantial portion of their bodies, this attention to detail in the appearance of the artificial limb is often very important to them. Carlos always keeps the final appearance in mind as he completes the fitting and alignment procedures, and will often make small changes that enhance the ultimate appearance.
He showed us several examples of his work, and the overall contours were as sleek and smooth as I have ever seen. There were literally no demarcation lines between the leg and socket portions, since the polyurethane spray bonded permanently to both cover and socket. The drawback to this approach is that the covering must be stripped off and re-sprayed to inspect or service the components, so this is not suitable for everyone. But, for experienced amputees who have a mature gait pattern and whose experience makes them confident that their components rarely need attention, this offers a great looking final result.
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Carlos prefers to use the Littig Strut in his fittings, and has a large experience with this component for both hip disarticulation and transpelvic applications. He had a transpelvic prosthesis in process while we were there, and showed us a socket design with proximal support that extended well up on the thorax on one side in an effort to stabilize a concomitant scoliotic curve.
Carlos prefers to use the most flexible Strut alternative for a given patient's weight, particularly for the initial fitting, because he believes the ability to deflect the spring under static body weight helps the amputee get a "feel" for how the Strut can facilitate hip joint flexion. During the dynamic alignment trials, he always attaches a temporary stride-limiting strap fashioned from one inch elastic webbing. Otherwise, the prosthesis will tend to take too long a step as the patient walks with more vigor. [In the finished prosthesis, the protective foam covering and spray covering provide this function.]
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The highlight of our visit was the chance to meet one of Carlos' local patients, a very articulate young professional who had been wearing a transpelvic prosthesis for several years. She reported that, in her experience, the design had been pretty durable and comfortable, and had worked well in her daily work setting as well as in her leisure activities. There was some obvious scuffing on the covering from the abrasion that is inherent in prolonged sitting and the associated weight shifting weight, but both she and Carlos pointed out that he could re-spray locally and overcome such normal wear and tear.
The most impressive thing for me was the chance to observe her gait pattern. It took about two steps for her to reach the cadence for which the Strut resistance had been optimized, but every step from then on was as fluid and symmetric as I have ever seen in a high level prosthesis. [Click here to download a short video clip to see for yourself, and try running it as a continuous loop to imagine what a series of steps would look like.]
This young lady was able and willing to walk continuously for several minutes, and could slightly vary her cadence, exhibiting no problems turning or slowing down or stopping ambulation. However, she was obviously getting winded and starting to perspire after continuously walking, so it is clear that even with a Strut it takes a lot of energy to propel a high level prosthesis.
In many ways, this visit on our trip illustrated both the state of the art as well as the limitations in current technology. With a concerted effort, physically fit individuals can obviously learn to develop a more normal gait pattern with a hip flexion bias component in the prosthesis, but it still takes pronounced effort to walk with a transpelvic or hip disarticulation prosthesis. There is still plenty of room for improvements in the function of prosthetic hip joint mechanisms, and a powered joint offering active flexion that is automatically cadence responsive would likely be a significant breakthrough for this population.