MARVIN GARDNER, M.E. EDWIN KINNEN, PH.D. MARTHA GRAM, B.S., R.P.T.
Children with severe physical handicaps that preclude standing and walking can be placed in orthoses at a very early age. Clinically, we have found that physical and emotional adjustments are improved if these patients can remain upright unaided and experience limited movement within their homes and schools. The parapodium has proved to be particularly useful for this purpose for children with spina bifida with myelomeningocele1.
As disabled children become somewhat mobile, they develop an interest in auxiliary devices to increase the range of their independent activities. Primary-school-age patients particularly would appreciate a hand-driven tricycle, both for recreation use in a gym or neighborhood setting, and for short-distance transportation. A tricycle, designed for this purpose, is described here for the potential benefit of any child.
Design and Construction
The design objectives were to construct a tricycle with hand-operated steering, propelling, and locking features for use by children wearing the parapodium. Operating mechanisms were to be adjustable to accommodate different arm and trunk dimensions. Also necessary was a broad seating surface at the level of a wheelchair to aid transfer to and from the vehicle, and a platform underneath to support the parapodium base and provide the rider with a sense of security. Finally, the trike had to be reasonably rugged to withstand abuse and neglect.
The design took maximum advantage of discarded bicycles and generally available new bicycle parts. Two sizes were constructed. These models are shown in Figure 1 . Some dimensional details are given in the Appendix.
The large, flat, padded seat helps the rider to transfer to and from a wheelchair. Alternately, a child wearing a parapodium can approach the trike from the side and then turn forward when fully seated. Seat height is adjustable. The seat belt and L-shaped backrest provide adequate support. The vertical distance from the hand crank to the base and the horizontal distance to the edge of the seat can be adjusted by loosening bolts on a pivoting and sliding support for the double chain drive.
The front axle has a coaster brake which allows the rider to reverse cranking motion to slow or stop forward motion. Three-speed gearing was found necessary because of the increased cranking effort required on a slight grade. This design had a three-to-one ratio between high speed and low speed. Approximately four lbs. of pull on the pedal will start the trike moving in low gear on a level surface. The shift lever and the console add eye appeal for the young rider. A cable-operated, caliper-type brake locks the trike for mounting. The operating lever for this lock is positioned just below the shift console in these models as seen in Figure 2 and Figure 3 , but it can also be located beneath the front edge of the seat.
The frames and drive trains were assembled from used bicycle parts, requiring two bikes for one trike. The smaller model, Figure 3 , has 16-in, pneumatic-tube wheels and was made from 16-in, bike frames. The larger one was made from 20-in, wheels and frames. The sectioned bike frames were gas welded to stock tubing for the trike frame. Lightweight expanded steel was added for strength and surface effects. Wheel fenders seemed superfluous but could be added. The complete fabrication procedure used modest machine-shop equipment.
The coaster brake, caliper brake, three-speed shift console, wire basket, tires, and tubes were purchased new. These items plus stock metal, paint, and incidentals resulted in a materials cost per trike of about $120.
The trikes proved to be reasonably stable as a result of the low profile and large rear wheel spacing. However, a determined rider can tip the vehicle with sufficient speed and a sharp turning maneuver. The unguarded lower chain section has not been hazardous. The wire basket on the larger trike, Figure 2 , provides carrying space; it also covers the lower rear-wheel cross-brace to discourage playmates from pushing and hopping on as a second rider.
Twenty-five trikes have been assembled, 10 of the smaller size. These are now being used by children in families of the Spina Bifida Association of Greater Rochester or by patients of the Birth Defects Center who have the trikes on loan.
Children and parents have found the hand-driven tricycle appealing for several reasons. With an appearance somewhat like the familiar trike, the disabled child feels more confident joining his neighborhood peer group in outdoor play. The child also becomes more mobile and independent. Patients have reported riding the trike to school and entering neighborhood "bike rodeos." Parents agree that the trike has increased their children's ability to find and socialize with friends nearby. Since isolation is a frequent problem of the disabled child, the hand-driven trike has potential value for assisting mental and emotional development.
Tricycles constructed from this basic design will be available for purchase in the near future from Community Playthings, Rifton, NY 12471.
This report describes the work and contributions of the Biomechanics Group of the Birth Defects Clinic, Department of Pediatrics, School of Medicine and Dentistry, University of Rochester, Rochester, NY 14642. Partial support for this work was obtained from a number of individuals and organizations within the Rochester community. Ideas for this trike were developed with the aid of a drawing of a "Therapeutic Type Bicycle" developed by Angelo Vittori, Chisholm, Minnesota.
- Motloch, Wallace M., The parapodium: an orthotic device for neuromuscular disorders. Artif Limbs., 15:2:36--47, 1971.