A Dynamic Solution for the Pediatric Symes Amputee
Taylor Mcleod is like any other 20-month-old child. He is full of energy and eager to explore the world around him. He climbs, toddles around, and gets into everything. But not so long ago, his mobility was greatly limited. As a unilateral congenital Symes amputee, every step was a struggle for Taylor. Now, thanks to his new articulated Symes ankle prosthosis (ASAP), he is able to walk, climb, and explore his world at will.
|From left: Daniel Record, CP, LP, RN; Taylor Mcleod; and Charles Kinne, CO.|
Taylor was born with a malformation of his left foot as a result of amniotic band syndrome (ABS), an in utero condition in which fetal parts—usually a limb or digits—become entrapped in fibrous amniotic bands. Without blood flow, the affected parts do not properly develop. Though ABS usually affects the extremities, it can also involve portions of the head or face. Malformation can range from stunted growth of the digits or distal lymphadema to more serious deformities, such as syndactlyly (webbed digits), limb-length discrepancy, and even amputation of all or portions of the limb.
In Taylor's case, the result was a nearly textbook Symes amputation. When he arrived at our Paducah, Kentucky, office for evaluation, he exhibited no leg-length discrepancy and appeared to have proper formation of both the calcaneus and malleoli. His lower-leg musculature appeared to be normal and well developed. Aside from his congenital abnormality, he was an otherwise healthy child. He was just beginning to become ambulatory and had progressed as far as physical therapy could take him without a prosthesis. The absence of his foot would not allow him to walk more than a step or two before falling.
When I met Taylor, one of my first concerns was that current prosthetic applications and componentry for the Symes amputee would not work well due to his age and small size. Pediatric componentry options were simply too heavy and cumbersome for a 20-month-old to use. It became readily apparent that Taylor would require a new and innovative approach. I consulted with my co-worker, Charles Kinne, CO, who has a great deal of experience working with pediatric bracing, in the hope that together we could contrive a better solution for this child by looking at the situation from both a prosthetic and an orthotic viewpoint.
Initial Evaluation and Considerations
We began with a thorough examination of our young client, which led to a few new concerns. Considering Taylor's age, our primary concern was that the prosthesis provide a natural gait pattern without compromising the toddler's physical growth and development. We therefore eliminated the option of a prosthetic socket design because it would be too constrictive and would not provide enough airflow to the limb. It would also not be lightweight, adaptable, or adjustable enough to accommodate for rapid changes in size and length. Other problems with a socket-type design included ease of application and comfort.
We were also concerned that the prosthesis not create a significant length discrepancy between the sound and amputated legs. This is a common problem with Symes prostheses, due to the added height of a foot attached to the socket. If we could avoid a length discrepancy, we wouldn't need shoe buildups on the sound side, and we could also prevent any spinal complications from improper pelvic alignment.
Our goal was to provide a dynamic prosthosis that would, if possible, allow for full range of motion at the ankle, thus allowing for full muscular development in the lower limb. Furthermore, it would promote a more natural gait pattern, lower energy consumption, and avoid risk of socket fracture, which is prevalent in Symes prostheses. In order to be functionally dynamic, we decided that the prosthesis must exhibit two characteristics: it must be self-suspending, so that it would not migrate and chafe the skin, and it must preserve proper ankle alignment to discourage tibial varum, which frequently occurs in mature Symes amputees.
|Detail of the ASAP.|
Our initial design began with a solid ankle AFO because of its lightweight construction and design. While this design lent itself well to our goal of minimizing leg-length discrepancy and allowing for adjustability, it would not provide the suspension needed to prevent migration, nor would it encourage natural gait, due to its non-articulating ankle. We decided to tackle the suspension problem first.
Suspension presented a big problem because standard suspension methods conflicted with our primary goal of minimal limb constriction. While proper suspension requires some compression of the residuum and friction on the skin, we wanted to minimize these forces in order to promote healthy movement and growth. To overcome this hurdle, we came up with a compromise. We started with an anterior locking shell and a soft toe filler attached to the foot plate of the AFO. We used a prosthetic sock, which acted as an interface to allow airflow to the residuum while allowing for the necessary tension on the skin. This was moderately successful but still problematic. We had to insert additional padding to the inner side of the anterior shell to gain purchase on the limb. The anterior shell was secured by a piece of two-inch elastic webbing that encircled the calf portion and was then secured with Velcro to the posterior of the prosthosis. This made donning the prosthosis easy.
|Anterior view of the ASAP in stance.|
A second part of the suspension equation was provided by bringing the proximal toe-filler over the dorsum of the residuum, providing a "cupping" of the anterior distal limb. Not only did this completely fill out the shoe, it also helped to provide a light capture and aided suspension while preventing trauma to the skin that could result from too much movement. After trying a number of materials, we found that Aliplast provided the best padding while maintaining a low coefficient of friction to prevent blistering on the anterior-distal portion of the residuum.
Preserving Ankle Alignment
At this point, we made alterations to the design to realize our goal of producing a fully articulating prosthosis. We started with the idea of using a free-motion joint for the ankle. Pediatric Tamarack joints were the obvious choice, due to their light weight and ease of use, but we didn't need their function as a dorsiflexion assist. Instead, we needed dorsiflexion resistance to support the child's weight and reduce energy expenditure by providing a smooth rollover at terminal stance. We used a pediatric joint and reversed it to produce the dorsiflexion resistance we needed.
Reversing the joints provided amazing results. It gave enough resistance to allow for full support of Taylor's weight and produced a smooth and effortless rollover. Within two weeks of wearing the ASAP, Taylor went from constantly falling to walking independently.
One particularly nice aspect of the design was adjustability. At his two-week follow-up appointment, Taylor's residual limb had atrophied very slightly and was beginning to piston in the prosthosis. By adding a layer of Plastazote to the inner anterior shell, we gained enough compression to achieve complete suspension. A thicker prosthetic sock could also be applied to tighten the fit. Another plus is that a variety of stiffer Tamarack joints are available to progressively match dorsiflexion resistance as Taylor's weight increases. Medium and adult joints can be substituted for the pediatric joints as necessary. The Tamarack joint is also consistent with the water-friendly design of this prosthosis, a plus for the patient and his parents.
The application of an AFO-type prosthosis and toe-filler proved to be a very rewarding experience. I was pleased to discover a new application with minimal limitations for pediatric Symes amputees. I was also happy to see that Taylor's family and physical therapist were pleased with his progress. They report that he is now able to climb and walk just as any boy his age would. But at the end of the day, the greatest reward came from seeing the smile on Taylor's face as he walked confidently across the room without a care in the world. O&P EDGE
Daniel Record, CP, LP, RN, is a district manager at Paducah Prosthetics, Paducah, Kentucky, a Physiocorp company. He can be contacted at