VASI Offers Advanced Pediatric Hand Technology

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By William J. Hanson, MS
Figure 1
Figure 1

The latest development in pediatric hand technology is the new Single Program-ming Module (SPM") circuit from Variety Ability Systems, Inc. (VASI) [Figure 1]. The SPM offers many features not previously available in prosthetic hand controllers. The circuit uses surface-mount technology, thus enabling VASI to make it lightweight and compact enough to fit all children's hand sizes from ages 1-11.

The microprocessor-based SPM circuit dramatically increases versatility and allows the use of a computer to set up and adjust the prosthetic system--an advanced feature that separates this controller from much of the competition.

The hand control strategy is downloaded from the VASI MyoWizard" system software [Figure 2]. This software has a patient evaluation mode that enables the prosthetist to look at muscle signal strength and adjust the prosthetic system to match the user's capabilities. VASI's proprietary interface software, MyoAssistant", displays simple bar graphs or time-history charts of muscle signal strength.

With the computer display, not only the prosthetist, but also the child and the parents can actually "see" the signals that are controlling the prosthetic system. Since many children are visual learners, this approach helps them understand what their various actions do--a concept that is often difficult for children to grasp.

Eight Control Strategies Available

Figure 2
Figure 2

At present, there are eight control strategies to choose from, based on the number of sites (one or two), the type of input device preferred (myoelectrodes, Touch Pads" or switches), and the output device (hand type). There are also many other control options which help the prosthetist match the control scheme to the patient's capabilities. Once properly set up, the system will be relatively easy for the child to operate because it has been "tuned" specifically for him/her. If the child needs a wrist rotator in addition to the electric hand, an LTI VariGrip" in-wrist controller can be used in lieu of the SPM hand circuit. This controller uses the same software, making it easy for practitioners to switch back and forth between them.

System Stores Information

The SPM and VariGrip prosthetic controllers have another interesting feature. They can store information about the prosthetic system's use, so the practitioner can review the information while servicing the prosthesis. The ability to reliably determine how frequently the prosthetic system is used and how it is being operated can be very helpful when dealing with children who cannot express themselves adequately. Usage information is also valuable when justifying the need for a new prosthesis. No longer must payers rely on "timeframe" when determining the need for replacement. Instead they can use the actual measured usage data.

For more information, 508.893.6363;

William J. Hanson is president of Liberating Technologies Inc., Holliston, Massachusetts.