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Resistance and comfort

Wrist ortheses made of resin and nanoparticles of clay are customized


A new material comprising a polymer resin covered with particles of nanoceramics, to be used in appliances to immobilize wrists and other parts of the body, was developed at the Federal University of Minas Gerais/UFMG. The nanocompound, created to be sold in kits and applied according to the need of each patient, can be sent to any destination in the world. “In the case of an earthquake, for example, this material can be sent on a large scale to immobilize arms and legs; this is a quick and easy way of providing medical care”, says professor Antonio Ávila, coordinator of the post-graduate course in mechanical engineering and advisor of the doctorate thesis that resulted in this new product. The product has already been patented by the university’s Coordenadoria de Transferência e Inovação Tecnológica, Department of Technological Innovation and Transfer.

One of the advantages of this material, in comparison with the imported material used in the appliances called ortheses is the cold-molding process. “When blended with the hardening liquid, the resin produces enough heat to mold the material”, says professor Adriana Valladão, from the occupational therapy department at the School of Physical Education, Physiotherapy and Therapy of the UFMG, who developed the material during her doctorate studies. The heating cannot be compared to the thermally molded imported material, a plastic which needs to be heated in hot water at a temperature of up to 70 degrees Celsius before it can be used. But the resistance and rigidity of the materials are very similar.

Cold-molding allows nanocompounds to be used also on patients with burns. “Outer layers cover a more rigid inner layer made of fiberglass material and nanostructured material to provide resistance”, Ávila explains. To make the patient more comfortable, the fiberglass material is covered with soft neoprene rubber, a synthetic material used in diving suits, for example. In the kits, the outer layer materials, the inner layer materials and the neoprene are packaged separately. The nanostructured material that covers the central part includes montmorillonite, a clay with high absorption capacity, which is treated and baked to transform into ceramic. “The ceramic we are working with is approximately 50 nanometers thick”, says Ávila. Brazil has a mine with this kind of clay, but the nanometric granulation processing is not done here because Brazil lacks the appropriate technology. One kilo of this material costs approximately R$ 20,00, which is appropriate for low-cost therapies.


Alternative materials
From the time she was in the master’s program, when she studied the mechanical characteristics of materials used for ortheses available in the market, Adriana realized that the variety of available products was insufficient. “All the products were imported and therefore expensive”, she says. From then onwards, the researcher decided to focus her work on alternative materials that would help reduce the costs of the public hospitals and of the Sistema Único de Saúde/SUS the Brazilian Public Health Care System. Initially, Ávila had thought of using nanostructured material for aeronautic applications, as an extension of his post-graduate studies in the field of airspace engineering at the US’s University of Arizona. Ávila concluded his post-doctorate studies in March 2004. Adriana had the idea of using nanoceramic in material for orthesis. Work on the project began in 2004 with funding from the Conselho Nacional de Desenvolvimento Científico e Tecnológico/CNPq agency and the Ministry of Health.

At first, the idea was to work with nanostructured material for wrist ortheses; however, this material can also be used for the neck, back and lower limbs. “We chose wrist orthesis because it is the kind of appliance used in various pathologies, such as carpal tunnel syndrome, tendonitis and other injuries resulting from repetitive movements, to minimize or reduce the movements of the wrist and thus minimize such symptoms as pain and tingling”, says Adriana. Carpal tunnel syndrome is a medical condition which occurs when the median nerve in the wrist gets compressed, causing numbness and tingling in the hands, especially at the finger tips. Twenty six people, whose average age was 22 years, took part in the evaluation of the orthesis. All of them carried out daily tasks, such as picking up heavy objects, typing, and eating. “The objective was to verify whether the orthesis would become deformed or not during these tasks and whether it would keep the wrist in the correct position”, says Adriana. When comparing the wrist orthesis developed by Adriana with the wrist ortheses made from thermo-molded material found on the market, the result was quite similar. “Although the rigidity was quite similar to the material currently being used, the orthesis made from the nanostructured compound is quite flexible, which provides a better fit around the patient’s hand and makes him more comfortable”, she says.

A cost analysis of the two materials showed that the one developed at the UFMG is 30% less expensive than the imported material. A 40 to 60-centimeter strip of imported thermo-molded material costs approximately R$ 400,00 while the manufacture of a wrist orthesis costs R$ 52,00. The same kind of orthesis made of nanostructured material costs from R$ 14,00 to R$ 17,00. “As the government spends around R$5 million annually for the financing of ortheses, the difference allows a higher number of people to be treated at the same cost”, says Ávila.