A Transitional Walking Device for Children with Cerebral Palsy

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A Transitional Walking Device for Children with Cerebral Palsy

Designers: Jonathan Brightwell, Cara Rouse, Nathan Fife
Client Coordinator: Scott Sall, Children’s Hospital of Alabama

 

The Client Coordinator is a physical therapist who specializes in working on motor coordination and balance with children who have Cerebral Palsy (CP).  He has found in the past that many of the CP children with whom he works have an extremely difficult time improving their gait with a traditional walker and even more difficulty transitioning from a walker to hand canes.  The four wheel pull-behind walkers that most of these children use are designed for the children to hold their upper body rigid, placing all of their weight on their arms and dragging their feet along with them.  The coordinator noticed that after using the walkers for a prolonged length of time, many of the children develop a rigid upper body and are unable to adjust to the upper body movement required to walk with hand canes.  The aim of the present project was to develop a transitional walker that will allow arm movement (flexion and extension) as in contrary walking (where the arm that swings forward is on the opposite side of the foot moving back).

The design was subject to the following constraints:  The device must emulate normal walking as closely as possible.  The device must accommodate children with CP ranging from 4 to 8 years old; up to 100 lbs. and a height range of 32 to 48 in (Krick, J Amer Diet Assoc, 1996).  Accordingly, the arm canes used in the design will need to be adjusted to the proper height for each child (16 to 32 inches).  The device also needs to have adjustments for the widths between the canes.  In addition, the handles of the canes should have a 360 degree adjustable range in the horizontal plane.  This will accommodate any abnormal hand position caused by CP.  Because children of different ages move their arms at different distances when walking, the length of forward and backward movement of the canes must also be adjustable.  Also, adjustments must require few tools.  The completed device should be transportable within the therapy room from the treadmill to the storage closet.  The budget for this team project was $1500 and the time allowed was approximately 4 months.

TECHNICAL DESCRIPTION

 

The device was designed specifically for an existing treadmill located in the Physical Therapy-Occupational Therapy Department of Children’s Hospital of Alabama. The device has two basic components: the drive-side and the non-drive side.  Both components are contained in rectangular boxes with a tube steel frame and are enclosed by 1/2 inch plywood.  Each box was painted with a jungle theme and a cheetah, leading the children to name the device the “Cheetah Walker”.

The drive side of the device (Figure 18) has a 3/4 horsepower Baylor Industrial DC electric motor with a gear reducer and runs at a speed of 68 rpm. The motor was attached to the frame using one eighth inch steel.  Sprocket 1 was attached to the gear reducer and is powered by the electric motor.  Sprocket 1 turns the chain and three more sprockets attached to the chain.  A pushrod is attached to sprocket 2, changing the rotational motion into linear motion.  The other end of the pushrod is attached to a 3/8 inch steel bar that is welded to a one inch steal tube. The steel tube has a ½ inch steel bar welded 7 inches above the attachment that is connected to the frame by two pillow boxes.  At the top, and perpendicular to the one inch steel tubing, is welded a 1.5 inch steel tube that holds the cane width adjustment tube.  Sprocket 3 was used to re-route the chain, preventing mechanical rubbing.

The non-drive side of the device is powered by the drive side by way of an axle that runs underneath the treadmill.  The chain on the drive side turns sprocket 4, which turns the axle. The axle is attached to the frame by two pillow blocks.  The axle has two breaks in its length.  These breaks are linked together by mated couplings.  The middle length of axle is supported by two pillow blocks that are attached to a separate 4.5 x 29 inch frame made of one inch steel.  The non-drive side has two sprockets which are attached by a chain. One sprocket turns with the axle. The cane movement mechanism works here in the same way as on the non-drive side. The cane mechanism has a retractable 1 inch square tube that is pinned inside the 1.5 inch steel tube from either the drive or non-drive side.  This allows for the 13 to 22 inch width for cane placement, accommodating different sizes of children.  At the end of the retractable bar is a clamp from a percussion stand.   The adjustability of this clamp allows for the 360 degree rotation of the canes.  Normal adult canes were cut in order to fit into the clamp and to fit our height adjustability specifications.  The final design is shown being used by a child with CP in Figure 18.  Total cost = $1260.

18 - transitional walking device118 - transitional walking device2
Figure 18.  Four year old girl using the transitional walking device while client coordinator Scott Sall of Children’s Hospital looks on. The “cheetah walker”, which contains the motor, speed reducer, chain drive and follower sprockets that result in hand cane motion (at left) and transfer rotation to the non-drive side via an axle (right).