Image: Gregory Doerr
Compared with adult amputees, the number of pediatric amputees is much lower. This means less research and fewer prosthetic options are available to children. However, more hospitals and manufacturers are beginning to develop custom prostheses for specific activities and are developing existing prostheses that are lighter and smaller so children can easily use them.
“I think the things we are always struggling with in pediatrics are the size, the weights and the availability of the componentry,” Don Virostek, CPO, LPO, director of orthotics at Texas Scottish Rite Hospital, told O&P Business News. “Typically [prostheses] come out in the adult population first and then are eventually shrunk down over time to be able to use more in the pediatric population. So we are always on the tail end of some of that development because more adult amputees are out there. [Manufacturers want] to get those products out to [adults] first and then it trickles down.”
But according to David Rotter, CPO, LPO, clinical director of prosthetics at Scheck and Siress and vice president of the Association of Children’s Prosthetic-Orthotic Clinics, some children do not always wear their prescribed prosthesis.
David Rotter
“There are kids born with upper limb congenital deficiencies that do just fine without a prosthesis and decide not to wear one at all. Where the fitting becomes successful is when the user gets or derives utility from the device and can do something more efficiently and quickly with the device that they couldn’t otherwise do on their own,” Rotter said.
“I think we are seeing in adults and especially in children that activity specific applications are becoming a more standard approach to care. Instead of thinking the child’s going to get a hook or a hand and that is it, it becomes what activities the child wants to engage in and how can we help facilitate that with the different types of appliances that are available or that we can custom make,” he said.
It is important for children with amputations to be able to enjoy the same activities as able-bodied children without feeling that they cannot perform as well because they are missing a limb. Recently, more companies have focused on developing prostheses that will help pediatric amputees pursue the sports and other activities they enjoy.
“For someone who wants to play guitar or shoot a bow and arrow or use a kayak or lift weights, these offerings are becoming more common, where in years past the focus was on what were perceived as ADL based ‘functional devices,’” Rotter said. “I think there is a better understanding now that often kids, especially congenital limb deficient kids, are well served by activity specific devices that could help them do things that they would otherwise have difficulty doing.”
According to Virostek, Texas Scottish Rite Hospital has designed custom devices to help children effectively continue with extracurricular activities, such as playing violin and bass drum, flag or baton twirling and cheerleading.
“We have [developed] a lot of specific types of devices to get kids to be active in whatever sport or activity they enjoy,” Virostek said.
Because children have the tendency to run around more often than adults, this has led to the prescribing of a more activity-specific running prosthesis, which in some situations is used as their main prosthesis.
“It is somewhat unique because those particular feet have no heels on them so the kids can’t stand in one position and balance easily,” Virostek said. “They tend to be on the tips of their toes and bouncing around, not in one position.”
“Our goal is still to get the kids to be as functional as possible [so it is important to make] the prosthesis lighter and stronger and allow children to get through their activity level so nothing breaks,” Virostek added.
Advances in socket design primarily for transfemoral deficiencies, suspension, prosthetic knees, prosthetic feet and myoelectric and external powered upper extremity prosthetics developed by the Department of Veterans Affairs have helped pave the way for pediatric prosthetics.
“Pediatric prosthetics are not just small adult prosthetics. Pediatric prosthetics are not simple or basic — there are unique issues and concerns (size, weight, clearance, durability, adjustability for growth, etc.) with the pediatric population. Typically, it takes a while until these innovations can be applied to pediatric prosthetics. However, it does occur in most cases,” JoAnne Kanas, PT, CPO, DPT, corporate director of orthotics and prosthetics at Shriners Hospitals for Children, told O&P Business News. “Our patients and families see these same innovations on TV, in magazines and online. They are a well-educated group and they will routinely come to our O&P clinics with printouts, photos and requests. While in many instances these options are not clinically applicable, we enjoy these discussions as it keeps everyone up to date and lets our families know what future options might be for them.”
Gait laboratory
When children are fit with a prosthesis, sometimes it does not fit comfortably or exactly as it should.
“What we are seeing now in the more recent innovations are the things that are coming down from the increased design and innovation from the war effort,” Freeman Miller, MD, of Nemours/Alfred I. duPont Hospital for Children, told O&P Business News. “Things like design of ankle joints are coming down to the pediatric level, but for smaller kids, especially for 7- to 8-year-olds, the problem with those joints is they are still a bit too big and not properly sized for pediatrics.”
At duPont Hospital for Children, Miller and colleagues use the gait laboratory to more precisely discern how a prosthesis affects a child’s ability to walk and move. Practitioners construct a 3-D computer model by recording a patient’s movement through a system of moving cameras and force plates on the floor. They then calculate the forces that are occurring at different joints.
Freeman Miller
“The gait laboratory has been developed primarily for doing evaluations of walking in children with complicated walking problems, usually with children with cerebral palsy,” Miller said. “However, we also do our prosthetic clinic in the gait lab because sometimes it is difficult to see whether the prosthesis is aligned as best as it can be. We use that system to assess the proper alignment of the prosthesis.”
Although the results gleaned from the gait lab cannot determine what type of prosthesis would best fit on a particular patient, it does show how the prosthesis should be adjusted for full comfort and is a good option for training patients how to walk with it
“About a year ago, we had a teenager who had a recent amputation and he was doing well with his temporary prosthesis, but when he got his permanent prosthesis he could not get comfortable with it. So we tested him in the gait laboratory and saw where there was a misalignment that was causing pressure in his knee joint and where the top of the prosthesis was fitting on the residual limb,” Miller said. “It allowed us to make some minor adjustments to the alignment that made him comfortable and then he ended up functioning well with his prosthesis. We do not have to do that with every patient we see, but we do it when there is a patient who is having problems and we can’t figure out what’s causing the problem.”
3-D printing
Another helpful tool used to advance pediatric prosthetics is the 3-D printer, which has provided opportunities for both amputee and able-bodied individuals to create prostheses that are simply constructed and less expensive than more sophisticated prostheses. However, one of the main drawbacks with 3-D printing is it may not create a durable product, particularly if plastic is used. Its use in pediatric prosthetics may be limited to upper extremity uses.
“Upper extremity prostheses for children need to be very light and, if they are only for cosmetic use, using 3-D printing might be an option,” Miller said. “The forces in current printable prosthetic material by itself are not strong enough. There are ways to add composite layers with carbon fiber, but it still requires having someone adjust the prosthesis. There is no system that I am aware of that can print ready-to-wear prostheses.”
There are various types of materials that can be used to print prostheses with a 3-D printer. However, most often ABS plastic is used, and, according to Rotter, this brittle material makes most manufacturers hesitant to use a 3-D printer, but they do use the device for prototyping.
“As far as upper extremity is concerned, 3-D printing could be more applicable to that kind of scenario where there is less of a weight bearing issue and less of a force is put on the device,” Rotter said. “The application that 3-D printing is used most widely for, right now, is prototyping shapes and then that would be converted to a different, stronger material.”
“Depending on the printer, you may be able to print something highly durable, but I would assume the cost would also be much higher,” Virostek added. “If you are making the components for the arm, 3-D printing may suffice, but to make a 3-D printed socket, I would think this would be difficult to accomplish on a large scale.”
For now, practitioners are still waiting to see exactly what 3-D printers will be able to provide before diving head first into investment.
“I think it is great that you have other people who are coming up with different interesting ideas and putting those ideas out there in the main stream press or on the internet for everyone to see,” Rotter said. Indeed, there are several examples of entrepreneurs using 3-D printing to create prostheses as a low-cost alternative to traditional prostheses (see For More Information). “I think that is a good thing because it stimulates thought, it stimulates ideas and a lot of the great ideas in our industry have come from independent people who had a great idea who wanted to see it to fruition.”
Improvements in pediatric prosthetics
While there is focus on providing children with prostheses that will help them participate in different activities, there are still existing prostheses that need to be redesigned with children in mind, such as knee and ankle joints and prosthetic feet.
“The most sophisticated prosthetics, like the ankle and knee joints, especially the knee joints that are computer controlled, are getting a size reduction, but because there are so few children some of those things are just very slow to not available,” Miller said. “While it wouldn’t make sense to have a sophisticated computerized controlled knee for a 2-year-old it would make sense to have it for an 8-year-old [child]. It is a problem of numbers. We do have reasonably good options, but some of those sophisticated new recent developments are not available for kids.”
Miller also believes research on understanding the relationship to a child’s size and the benefit of having ankle articulation vs. simple feet that are lightweight would be beneficial to children in the long run. Since sophisticated knees and ankle joints are not yet available for children, often adolescents and teenagers are prescribed lightweight adult knees. However, not only are the lightweight adult knees too big for children, they also do not provide the best mobility for pediatric patients of any age.
“I have always thought kids with lower limb [amputations should have] knees that respond to speed. We concentrate hydraulic technology in the adult population, 
but the kids would really be the best beneficiaries for that because they go from walk to run to walk routinely and the prosthetic knees haven’t caught up with that yet,” Rotter said. “Adolescents are often forced to use lightweight adult knees, so I think that is an area for improvement with children.”
Besides developing better knee and ankle joints for children, Miller reminds practitioners it is important to keep an eye on the growth of their pediatric patients. Children experience a lot of growth in the length and alignment of the limb, but if they have a residual limb that is very short, there are advancements in orthopedic management so the residual limb can be lengthened for a better prosthetic fit.
“It is important to constantly pay attention to the length of the residual limb that we consider ideal for prosthetic fitting as the child grows,” Miller said. “I think sometimes, if we think about all of the modern sophisticated technology that’s available to build prostheses, we can lose sight of the fact that we also have to keep in touch with the child and continue to monitor the child’s growth, especially as it relates to the amputated limb so that we end up with an optimal limb.” — by Casey Tingle
Disclosure: Miller is employed by Nemours/Alfred I. duPont Hospital for Children, Wilmington, Del. Kanas is employed at Shriners Hospitals for Children, Tampa, Fla. Rotter is employed at Scheck and Siress, Chicago. Virostek is employed by Texas Scottish Rite Hospital for Children, Dallas.
