Marriage of High and Low Technology in Peruvian Wheelchair Design

by Marc Krizack (krizack@sfsu.edu)

A Peruvian medical student and a North American rehabilitation engineer have teamed up to create low-cost customized wheelchairs using special computer software and a toy-sized wooden seating simulator to aid in the customization process.

In 1997, John Olivera Vilcapoma, a physical therapist in Lima who is currently studying neurosurgery, and Todd Lefkowicz, a mechanical engineer at the University of Washington in Seattle, began a six-month project in Lima to provide low cost wheelchairs for disabled children with cerebral palsy and special seating needs.

A New  Paradigm

Usually, customized wheelchair seating starts with a standard wheelchair frame or base on which is then mounted the seating system which was designed for a particular child.  What is especially intriguing, and possibly unique, about this project is that it starts with the special seating needs of the child, then redesigns the wheelchair frame to accommodate the individualized seating.

The idea for reversing the standard order of custom seating design developed out of problems that Vilcapoma and Lefkowicz encountered in trying to use adjustable mounting hardware on existing slingseat wheelchairs.  They found that the mounting hardware was one of the most difficult and time consuming components of the system to build, leading to a substantial increase in costs.  They reasoned that if the wheelchair frame, which often had to be customized anyway, were designed after the seating was designed, the need for mounting hardware would be eliminated.

The problem with this idea, however, was that to redesign the chair in every instance in order to save the time and cost of fabricating and installing mounting hardware for the seating could actually increase total cost.  Redesigning a wheelchair is not a simple process.  A change in the dimensions of one part of the chair often requires corresponding changes in other parts.  A change in seat angle, for example can require changes in the length of the seat rail tubes and the locations of bends in the tubing would have to be recalculated as well.

The Magic of Computer Assisted Design

To solve this problem, Lefkowicz and Vilcapoma decided to design a hand-held wooden seating simulator to allow Peruvian rehab professionals to establish the required seating angles for each client.  He then created a software package that would allow rehab professionals to make rapid redesigns to the chair simply by plugging in the new dimensions.  If the angle of the seat was changed, the computer program would automatically recalculate the other necessary changes and redraw the new chair, like magic.  The program also shows how to assemble the re-sized tubes so they can be welded at the proper angles.

To accommodate this method, Lefkowicz chose an early model of the Whirlwind Africa-I wheelchair, designed by Whirlwind Wheelchair International of San Francisco State University.  The Africa-I is widely available in Peru.  It has a folding x-brace, but unlike most folding chairs, the seat rail tubes are not connected to the backrest tubes.   This feature allows the chair to fold even if the seat rail tubes are not at 90o angles to the backrest tubes.  This characteristic facilitates custom design changes to the wheelchair frame to accommodate a wide range of seating systems which then can be mounted flat against the seat rail tubes without the need for traditional mounting hardware.

The system's maiden voyage proved successful.  The builders were able to incorporate all the dimensions calculated by the software program into the resulting wheelchair, which sold for US$200, US$70 less than a traditional design wheelchair manufactured by the same shop.

DOS-based Program

The software program that Lefkowicz designed is DOS-based, which means it can run on any PC-compatible computer, including those built in the 1980's when a 286 felt as fast as the Concorde, a 20 megabyte hard drive seemed unfillable, and one megabyte of RAM was so excessive that only the rich and the nerdy had it.  Lefkowicz hopes to further refine the software program, make it easier to use, and offer more design options.

Lefkowicz, who is the new co-chair of RESNA's Special Interest Group-17, Appropriate Technology in Developing Countries (SIG-17) for 2000-2001, stresses that this method is only a tool, albeit an important one, in meeting the seating needs of disabled children in Peru, and by extension, around the world.  The most important element, says Lefkowicz, is "educating other Peruvian rehabilitation professionals about the benefits of special seating and positioning, helping them get more experience, and improving the quality of their interventions."

Todd Lefkowicz can be reached at ToddL@u.washington.edu