Sustainable O&P Fabrication for Developing Countries
February 2011 Issue
"Live simply, so that other people can simply live." —Mahatma Gandhi
Polystyrene "beads" in beanbag chairs. Coffee beans and tea leaves packed in vacuum-sealed bags. Sand on a beach. New prosthetic technologies for developing nations. These seemingly unrelated items inspired Yeongchi Wu, MD, then director of research at the Center for International Rehabilitation (CIR), Chicago, Illinois, and his team to create a simpler, less expensive, and more sustainable casting technique for fabricating prosthetic limbs in developing countries. "Although the cost-effective green technology was developed for low-income countries, I believe it also can be very useful here [in the United States]," Wu says.
Developing the technologies, systems, and clinical protocols to meet the need for prosthetic care in developing nations, and even in more developed nations such as India and Thailand, which struggle with some of the same issues, is a challenge. Many individuals who have undergone amputation live in impoverished areas still reeling from the effect of recently ended or ongoing armed conflict. Large numbers of persons with one or more amputations live in remote rural areas far from urban hospitals and prosthetic facilities. To reach medical and prosthetic care, these patients must take precious time away from families and work to travel for days over difficult and often dangerous terrain.
There is an ongoing need for appropriate technology, which the International Society for Prosthetics and Orthotics (ISPO) defines as "a system providing proper fit and alignment based on sound biomechanical principles, which suits the needs of the individual and can be sustained by the country at the most economical and affordable price."
Researchers, engineers, physicians, prosthetists, and other professionals involved in rehabilitation are stepping into the breach to develop appropriate technologies to aid amputee survivors of war, poverty, disease, and natural disasters in the developing world. Among these professionals are Wu and his CIR colleagues, including Hector Casanova, CP, and colleagues at the Northwestern University Prosthetics-Orthotics Center (NUPOC), Chicago, Illinois. Although Wu is now semi-retired, he continues to write papers related to research and development work, prepare grant proposals, and conduct distance learning courses.
Under a series of grants from the National Institute on Disability and Rehabilitation Research (NIDRR), the CIR established the Rehabilitation Engineering Research Center (RERC) on Improved Technology Access for Landmine Survivors (1997-2003 and 2003-2008). (Author's note: For more information about the CIR, visit www.cirnetwork.org)
One RERC project aimed to develop appropriate fabrication technologies that would be timely, cost-efficient, and improve service delivery to more patients and would be sustainable through local rehabilitation programs. The CIR casting systems originated from a matrix primarily focused on helping landmine survivors.
Even in areas where hostilities have long since ceased, landmines continue to be a lurking scourge. Within the past several decades, the mines have caused hundreds of thousands of casualties worldwide, with large numbers of victims throughout Asia, Africa, and Latin America. Survivors often struggle with the aftermath of horrific injuries.
Although the CIR Sand-Casting System and the newer version, the CIR-Wu Casting System (also called the CIR PS Casting System), have been used in several countries, Thailand and India have seen the widest use. Both of these countries have suffered a substantial number of landmine casualties. The heavily mined borders between Thailand and its war-torn neighbors, Cambodia and Myanmar, are a constant source of danger.
Seeking a New Approach
Plaster-based casting has been the most common casting procedure used in low-income countries; however, its use is sometimes problematic. Plaster may not be available in some countries, and plaster casting creates non-recyclable waste that has to be collected, transported, and disposed.
Wu and his team looked for a new approach. Wu was intrigued by the dilatancy (the tendency of a compacted granular material to dilate and increase in viscosity as it undergoes shear stresses) system used in wheelchair seating and positioning. This phenomenon is identical to the technique used to vacuum pack items such as coffee beans or tea leaves for sale in grocery stores—under vacuum, the food becomes a solid mass.
Wu saw dilatancy as a potential alternative for plaster of Paris because it would not require complicated set-up equipment and it would eliminate the availability problems associated with plaster.
"We tried many types of granules such as rice, mustard seeds, poppy seeds, tea leaves, coffee powder, plastic beads, scraps of polystyrene boards, etc.," Wu says. The team ended up choosing polystyrene (PS) beads. "Because they are lightweight, PS beads can simply be wrapped around the limb in the casting bag, unlike most heavy casting materials that require compressed air for fluidization, which is essential for the residual limb to insert into the casting materials [sand] in the CIR Sand Casting System," Wu explains.
Wu's artistic interests also played a part in developing the prosthetic-casting technology. In addition to his medical career, Wu is an artist and sculptor whose work has been collected by many art enthusiasts. Wu has illustrated most of his publications himself. "At a foundry I observed the process of fluidization, which involves high-pressure pumping of high-pressure air into silica sand, being used in lost-wax casting for bronze sculpture," he says. "This was adopted in the CIR Sand Casting System." In turn, the technique used in the new CIR PS Casting System will eventually be applied in sculpture and ceramics, he adds.
CIR Sand Casting System Breaks New Ground
After laboratory and field-testing in El Salvador, the CIR Sand Casting System was presented at the 11th ISPO World Congress in Hong Kong in 2004, followed by a yearlong ISPO-sponsored independent evaluation at the Vietnamese Training Centre for Orthopaedics (VIETCOT), Hanoi. The key components were a 24-inch high, eight-inch diameter PVC pipe sand container, clean dust-free sand, a vacuum pump with a large reserve tank, and an air compressor.
The results were better than historical reports of fittings with plaster of Paris casting by qualified prosthetists, according to the paper, "Sand-Casting Technique for Transtibial Prostheses," by J. Steen Jensen, P.A. Poetsma, and N.H. Thanh, published in Prosthetics and Orthotics International, August 2005. The authors note, however, that the fit was consistently larger than the residual limb, but add that total contact could be achieved by applying from two- to five-ply socks.
The system uses four basic steps, as outlined in a technical note, "CIR Sand Casting System for Transtibial Socket," by Wu, et al., Prosthetics and Orthotics International, 2003, 27, 146-152:
- Prepare the residual limb.
- Create the negative mold.
- Form and modify the positive model.
- Make a soft insert and vacuum form the socket.
A custom-made transtibial prosthesis can be fabricated for final dynamic alignment in about 90 minutes. (Author's note: That fabrication time has since been reduced to about an hour. To see a video of the process of duplicating a plaster model into a positive sand model in 50 seconds, visit www.ideanet.org/gallery/technology_details.cfm?galleryid=5B5D76735340 or www.youtube.com/user/CIRNetwork#p/u/8/DemNEFRGceA)
New CIR PS Casting System Debuts
In 2005 Wu and his team introduced an improved version of the casting system, the CIR PS Casting System, which was initially called the CIR-Wu Casting System or the CIR Casting System. The new version is less expensive to set up, requires less equipment, is lighter, smaller, and more portable, and captures a better-quality impression.
The biggest difference is that PS beads, which weigh only about one-tenth as much as sand, replace the sand as casting material. An elastic fabric bag replaces the PVC container, and the air compressor is eliminated.
Both versions also have an advantage over plaster of Paris in that the casting materials are reusable, thus eliminating waste and reducing costs.
The same ISPO team that tested the original system in Vietnam tested the new version, giving it a thumbs up.
In their paper, "Preliminary Experiences with the CIR Casting System for Transtibial Prosthetic Sockets," published in Prosthetics and Orthotics International, June 2009, the authors note that a good fit was obtained in a greater majority of cases than with the sand-casting technique and that there was a highly significant reduction in circumference measurements on the positive model. Unlike heavy sand that sediments to the lower end of an object, the micro-PS beads contained in a small fabric bag can be evenly distributed manually around the limb, similar to pressure casting, thus providing a better fit. The new CIR PS Casting System outperformed traditional plaster casting as well, according to the researchers. "The sockets manufactured in this small pilot series only required one one-ply sock to achieve a total contact fit, meaning with the full stump end, no open-ended sockets. This can be difficult to obtain with plaster casting even in trained hands," the authors point out.
Unlike the older sand-casting system, which can only be used for transtibial prostheses, the CIR PS Casting System, with different sizes of casting bags, can be applied to all levels of amputation, as well as for some orthotic applications. The steps for fabricating a transtibial socket are as follows:
- The casting bag filled with PS beads is rolled over the plastic-bag-covered residual limb and air is evacuated from the sealed casting bag to form the negative mold in a minute or less.
- The negative mold is then filled with casting material such as sand or glass beads to convert it into a positive sand or glass beads model.
- Once the positive model is formed through the application of vacuum pressure, the PS casting bag is disconnected from the vacuum and removed to reveal the positive model.
- The positive model is modified for pressure relief and weight-bearing before vacuum forming the socket.
- De-molding is performed by cutting open the plastic bag and draining out the sand or glass beads, which takes about 15 seconds.
A person who has experience in this method can fabricate a transtibial socket in about 30 minutes, and Wu notes that a person with an amputation can be on his or her way with a new prosthesis within about two hours of arriving at the clinic.
The technology earned Wu and his team recognition at the 13th ISPO World Congress held in conjunction with the ORTHOPÄDIE + REHA-TECHNIK international trade show May 10-15, 2010, in Leipzig, Germany. Wu's paper on the CIR PS Casting system, titled "CIR TF Casting System for Making Transfemoral Sockets," received the "Best Paper" award in craft/trade for technical innovation. (Author's note: To see a video of the CIR PS Casting System in action, visit www.ideanet.org/wu-temp/wu_casting_system.cfm)
Creating Elephant-Sized Prostheses
An adapted version of the system has been successfully used to fabricate prostheses for two gargantuan patients in Thailand—elephant landmine survivors Motala and Mosha.
In 1998, Motala, age 38 at the time, was working in a logging camp along the Thailand-Myanmar border when a landmine suddenly exploded, shattering her left front foot. With her mahout (keeper and trainer), the three-ton elephant walked for three painful days to reach the Friends of the Asian Elephant (FAE) hospital in Lampang, Thailand. Her foot was beyond repair, and a 30-person team, including doctors and veterinarians, worked for four hours to amputate the infected tissue. Afterward, she was fitted with a canvas bag filled with sawdust to help her move on her amputated leg.
Motala's story captivated the public and media in Thailand and around the world. In 2006, she was joined by a baby elephant, Mosha (pictured above), who was just seven months old when she lost her right front leg to a landmine. Mosha, whose name means "star" in the Karen language, became an international star in 2009 when she became the first elephant to be fitted with a prosthesis.
Later, Motala was also successfully fitted with a prosthesis.
Therdchai Jivacate, MD, secretary general of the Prostheses Foundation of HRH The Princess Mother in Chiang Mai, utilized the CIR PS Casting System as he lent his expertise to help Mosha and Motala. Although the Foundation has fitted more than 16,000 human amputees, Mosha was Jivacate's first pachyderm patient. "When Mosha first saw her artificial leg, she was scared of it," a keeper said in a BBC news story dated March 10, 2009. "But as soon as the doctors put it on and she could put some weight on it, she didn't want to let them take it off."
Mosha's socket was fabricated from 12mm-thick high-density polyethylene (HDPE). The HDPE sheet was heated in the oven at 160 degrees Celsius (320 degrees Fahrenheit). When sufficiently softened, the sheet was wrapped on the modified plaster residual-limb mold, which had been previously covered with a soft Pe-Lite® sheet.
After hardening, the socket was removed from the mold. After trimming the socket edge, Jivacate placed it on Mosha's residual limb and had her weight bear on the affected leg. When Mosha showed no sign of pain or discomfort, the socket was then used for her prosthesis.
Some creative, out-of-the-box thinking went into the design and fabrication of the prosthesis. The shank connecting the steel socket holder to the foot plate was made of two-inch-diameter stainless steel. The connector between the shank and foot plate was made from a hard rubber bumper, which was used to absorb vibration between the engine and chassis of a pickup truck. "This bumper worked as a shock absorber and wrist joint, which can help Mosha walk better, especially when going up and down hills and over uneven ground," Jivacate explains. Polyurethane foam under a steel cover composed the foot plate.
Following Mosha's successful prosthetic fitting, Jivacate used the same methodology to fabricate a prosthesis for Motala that same year. In 2010, both of the elephant amputees received new prostheses.
Kudos for the Innovative System
Jivacate, whose foundation is the only facility in Thailand that provides free prosthetic care to impoverished amputees, is an enthusiastic proponent of the CIR system. The foundation began using an adapted version in 2008, and as of April 2010, the foundation, including its mobile-outreach clinics, had made 1,740 prostheses using the system, including 1,363 transtibial, 49 Symes, 302 transfemoral, and 26 knee disarticulation. "I think the CIR casting technique is the answer to making properly fitted sockets [in our region]," Jivacate says. "It is easy to use. This technique can save a lot of money, and polystyrene beads and sand can be reused again and again."
The CIR system also is widely used in India although the exact number of people who have been fit using this method is not available. According to Tarun Kumar Kulshreshtha, former director of the BMVSS-Jaipur Limb Program in New Delhi, India, the advantages of the system include ease and speed of use, the efficiency of prosthesis fabrication, and cost-effectiveness. However, Kulshreshtha says that the biggest advantage is the elimination of plaster of Paris. "The material used in the CIR PS System is reusable, and the system is neat and clean. Moreover, for an organization like us which receives large numbers of amputees, using a reusable material is always welcome."
Soikat Ghosh Moulic, assistant director, Prosthetics, Orthotics & Therapy Services, Partner Support, Mobility India in Bengaluru, adds, "The new CIR PS Casting System is an innovation that could sort out lots of issues related to the conventional methods of transtibial casting methodologies. The present system is easy to handle and most economical. The positive mold is ready in [a] few seconds with sand and is as good as plaster of Paris models. We are in a position to fabricate the socket within 30 minutes, and the service user is able to take the first trial within an hour's time.... The technology could be a boon for the developing countries like India and its neighboring countries."
Wu's Guiding Philosophy
Wu continues to develop new processes and devices to help improve care for individuals with disabilities, citing among his early influences Henry Betts, MD, former medical director and chairman of the Department of Physical Medicine and Rehabilitation of the Northwestern University Feinberg School of Medicine, and former medical director and CEO of the Rehabilitation Institute of Chicago (RIC). In a lecture to residents back in the 1970s, Wu recalls Betts saying, "Anything that improves the impaired function can be a potential therapeutic technique, even a better way to tie a shoe," to which Wu adds, "everything can be better, cheaper, and/or faster, as well as environmentally friendly."
Miki Fairley is a freelance writer based in southwest Colorado. She can be reached at