EMS aid development of prosthetic hand for children

Citation

(2002), "EMS aid development of prosthetic hand for children", Assembly Automation, Vol. 22 No. 1. https://doi.org/10.1108/aa.2002.03322aaf.001

EMS aid development of prosthetic hand for children

EMS aid development of prosthetic hand for children

Keywords: Motors, Prosthetics, Actuators

Nature and circumstance can be equally cruel, never more so however than when children are involved. It is thanks to the good work being undertaken by the Bio- Engineering unit at the Princess Margaret Rose Orthopaedic Hospital in Edinburgh, part of the Lothian Primary Care NHS Trust, that much of the pain and trauma is alleviated for children who through nature or circumstance, have lost a hand.

Aldermaston based Electro Mechanical Systems Limited has provided products and technical guidance on small DC motors and gearheads to the development team at the Princess Margaret Rose Bio-Engineering unit in order that they produce a child size artificial hand that offers realism and functionality, thereby enabling youngsters to move, pick-up and place objects with relative ease (Plate 1).

Plate 1

Though still in the clinical trials stage, the development team is hoping that someone will provide additional funding so that the project may be completed and the hands be made available to those who need them. It also needs to be said that the self-esteem and self-confidence of the recipients is raised to such a degree that they become well adjusted adults, able to lead relatively normal lives.

Presently the prosthetic hands are covered using PVC, the standard material used throughout the industry. It is not however, without its disadvantages. PVC for example soaks up newsprint and is harder to clean than the alternative silicone covering used on some prosthetics. Silicone has a better 'depth' of colour than PVC and is therefore more realistic. Coverings are cast from the hands of volunteers so have all of the features and appearance of natural skin.

The development programme has lasted for some twenty years. David Gow, the Director of Rehabilitation, Engineering Services, has been with the project from day one! It goes without saying that his knowledge is second- to-none and his value to the team which is in the world's top five in its field, is beyond calculation. We gratefully acknowledge him for providing the photographs used in this article.

The Edinburgh group first developed an adult size mechanical hand while a similar project in Sweden was working on a child's hand. The problem with mechanically operated prostheses is that a high degree of wrist muscle development is required to operate the limb successfully. This is usually present in adults but not in children. An electrically operated prosthesis would be the answer. David Gow is gracious in his recognition of EMS who he says have been working with him from the commencement of the electronic hand programme.

Happily, Aldermaston based EMS, now arguably the UK's leading provider of specialised small drive products, were able to help because market led demand for smaller motors and gearboxes in the micro drive area accelerated existing development programmes to such a degree that ultra compact, high power-to-weight ratio units ideally suited to the Edinburgh team's application soon became available.

In the current generation of child size prostheses, EMS provide two 10mm diameter planetary gearheads (Product Ref 1016M006G), offering 64:1 reduction whilst the equivalent adult prosthiesis uses a single 10mm diameter unit (Product Ref 1016M006G), along with a 14mm unit (Product Ref 1319E006S) which offers 43:1 reduction. In both cases the drive motor is located in the thumb. All are compact, powerful, extremely light weight and reliable.

It is now possible to fit electrically operated hands to children of just two years of age. Experts say that this is the ideal age for children to receive a hand as limbs fitted later than this are often discarded by the user. From 2 years to adulthood, three sizes of hand are generally required. The smallest hands weigh just 130 grammes inclusive of its external battery and the hand is removed for recharging. A one-hour charge gives four-to- five hours operation.

Obviously the hope is to develop an internal battery at some point which will make the limb completely self contained and more convenient to the wearer. At £5,000 to £6,000 each, they are not cheap but production on a commercial scale should see the unit price fall considerably. Smaller limbs, when superceded by a larger limb on a growing child can be refurbished but at present this seems not to be economically viable.

For further information contact Jeff Mead, Electro Mechanical Systems, Eros House, Calleva Industrial Park, Aldermaston, Reading, Berks, RG8 7LN. Tel: 0118 9817 391; Fax: 0118 9817 613; E-mail: jmead@ems-ltd.com ; Web site: http://www.ems-limited.co.uk