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Prosthetics virtual trainer

Adapting to a prosthesis or a transplant could be very challenging, as they are pieces foreign to the body and thus is a process in which the mind and body has issues and may take significant time.

Reeducating the body to accept a prosthetic is a hard task for which science and technology have tried to assist; in the past two decades materials are becoming lighter and more functional thanks to the appearance of new materials, such as titanium and advancements in computer science and robotics. Despite the aforementioned, two of every 10 people cannot adapt or cannot maneuver their new alien objects.

Prosthesis rejection happens in part because they are heavier than expected or because during rehabilitation they did not work on specific functions of the new prosthesis. This process includes strengthening exercises to recover the strength they had in the muscles before the amputation and basic muscle signal detection during the contraction and relaxation processes (electromyographic signals) with the purpose of achieving better movement of the apparatus.

To train people without upper limbs or hands and help them during the adaptation process before receiving their definitive prosthesis, Universidad Nacional de Colombia (UNal) Engineering and Industrial Automation Master´s degree holder Johanna Carolina Chico Moreno created a virtual tool she named Dharma 1.0, a tool which helps test the movement capability by means of electromyographic signals in a virtual 3-D virtual prosthesis.

Rehabilitation, a fundamental step

Universidad Nacional University Hospital Physiatrists and Department of Physical Medicine and Rehabilitation Professor Dr. Octavio Silva, says that currently when an extremity is amputated the amputee goes through a mental process which is supported by psychology and psychiatric personnel. The process then continues with pain management before and after surgery in order to avoid phantom limb syndrome, which is the sensation that an amputated or missing limb is still attached to the body and despite not having the limb; amputees can still feel pain in the phantom limb.

During surgery, specialists take special care for the stump to be in conditions to receive the prosthesis and avoid deformation caused by muscle or joint retraction. Afterwards, they carry out the first phase of rehab where they reeducate the sensitiveness of the affected area with minor stimuli so the stump can later tolerate friction.

In the following phase, joint mobility is restored and muscles are strengthened by opening and closing hand exercises as well as forearm movements known and pronation and supination movements.

These types of movements are detected or read by a biofeedback technique in which a series of sensors are placed on the amputated member to detect muscle electric impulses which are indicated in a display showing a series of colored bars depicting movement direction.

How Dharma 1.0 works

The system integrates sensors and virtual reality. The prototype uses a sensor which acquires spatial data and arm electromyographic signals. Then two 3-D had prosthesis models and a software program generate a picture of the movements carried out by the patient.

The program uses a set of images or intuitive graphic interfase which produces an immersive environment to the patient. In other words, it makes the patient feel as if rehab was happening on its own hand or arm.

To test how Dharma 1.0 worked on commercial prostheses the first version of the prototype setup two prostheses, models E-nables´ Flexy Hand and Michelangelo manufactured by Ottoback. The former is an open source (it can interphase with any system) model  and very accessible due to its low cost in comparison to the latter model which costs approximately US $30.000 which features more than seven functions and separate thumb movement.

Furthermore, in the system created, the electromyographic signals are no longer depicted as bars and allow carrying out different activities to strengthen the muscles and maintain a follow-up of the progression of training in one or more patients.

The creator of the prototype says that “although implementing the tool does not ensure the prosthesis will not be rejected, it does reduce rehab time by a quarter –although rehabilitation times vary according to each particular patient– but also prosthesis adaptation and maneuverability are improved”.

Professor Silva also added that “the virtual tool aids the rehabilitation process for all types of amputees and has turned into another virtual reality tool with people with movement complications”.

“The virtual tool aids the rehabilitation process for all types of amputees and has turned into another virtual reality tool with people with movement complications”.

Optimal signals

The effectiveness of the tool was tested on male patients without a left arm. The first patient was a 52-year old male which had been amputated at the forearm due to an occupational accident which occurred 18 years ago and the second was a 19-year old congenital amputee.

Both subjects used the arm band (with the sensors) and they performed flexing, extension, hand closure and grip exercises with the virtual prosthesis. They also had to grip and sustain a cube in their hands. Tests showed that both patients correctly sent and received electromyographic signals.

Patient performance was similar in almost every phase of the tests, however researcher Chico said the first patient stated having initial difficulties because he had previously used a prosthesis and occasionally had phantom limb syndrome, which conditioned his movements. On the other hand the second patient, despite not having previous experiences using a prosthesis, had a quick adaptation in a virtual environment.

The scope of Dharma 1.0 is promising as the creator is planning to extend patient immersion by using virtual reality helmets which provide a more real rehab scenario. Furthermore, they will include different types of prosthesis in order to create a database and carry out patient follow-ups and assign individual therapies.

The scope of Dharma 1.0 is promising as the creator is planning to extend patient immersion by using virtual reality helmets which provide a more real rehab scenario.

By using a 3-D model they can also manufacture personalized devices, transforming the current prosthesis manufacturing standardized process.

The virtual tool created by Colombian technology could turn into a personal ally of the medical personnel during the rehab process for any patient with motor difficulties and will also allow amputees to have a closer relationship with the prosthesis which will become part of his/her new daily life.

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