Notes On Items Under Study At O.C.C.C.

Notes On Items Under Study At O.C.C.C.

Various members of the staff of the Ontario Crippled Children's Centre and the Prosthetic Research and Training Unit have prepared brief reports on selected prosthetic and orthotic items which are under development and study at the centre. Randy R. Mutrie, M.D., is Medical Director of Ontario Crippled Children's Centre and Mr. Colin A. McLaurin is Director, Prosthetic/Orthotic Research Projects.

-Editor

The Three-Wheeled Electric Cart

by Barbara Devitt, O.T. and William F. Sauter, C.P.O.(C)

To provide faster mobility for a child with quadrimembral phocomelia who had been using a Swivel Walker, an electric cart was developed. In one model it has two wheels in front and the U.S. Manufacturing Company powered wheel is installed in the rear as a propulsion unit (Fig. 1 ).

The three-wheeled electric cart has been designed so that it may be used by a child in either a standing or sitting position. However, the steering mechanism must be changed with each change in position. For standing operation a plywood platform about three-quarters of an inch from the floor is used (Fig. 2 ) so that the child may walk on to the cart with the Swivel Walker. The cart is steered by means of a special tiller bar which is shaped to fit around the child's torso just under the axillae. When the child leans either to the left or to the right, the drive wheel steers in the appropriate direction. Forward or reverse motion is selected by means of a lever switch mounted on the tiller. Note that when the cart is operated in the standing position the main drive wheel is in front and the other two wheels trail along like in a tricycle, the reverse of the situation shown in Fig. 1 .

When the cart is used with the child in the sitting position, the mounting platform may be removed to provide greater ground clearance. The child sits on the battery box facing in the opposite direction with the main drive wheel behind. In this position the child may drive up to a table or desk without hindrance. In the sitting position a different type of tiller is used but steering is still achieved by side-to-side motion.

The child was initially apprehensive about the powered cart but soon learned to steer it very accurately in either the standing or sitting position. She has taken the cart home and it is not yet known whether the standing or sitting position is preferred. The cart is operated in the sitting position only when the prosthesis is not worn and she is then unable to dismount without assistance. It is hoped that in the standing position the child can get on and off without assistance and so retain continuity of locomotion with either the Swivel Walker or the cart.

The Electric Elbow

By Kaare Lind Design and Development Technologist

The first prototype of the new electric elbow has been completed (Fig. 3 ). It was demonstrated at the CPRD Workshop on Powered Elbows at Santa Monica in October 1968. This elbow has been designed so that it may be used in a conventional prosthesis. It attaches to a standard Hosmer turntable and a standard Hosmer forearm saddle in the conventional way.

The first model fits the child-size Hosmer equipment only and is slightly heavier and slightly larger than the conventional child's elbow. The motor and switches are mounted within the elbow shell and control is obtained by use of a conventional elbow-lock control strap. A gentle pull causes the elbow to flex and a strong pull causes the elbow to extend. No adjustment to conventional harnessing is needed. The only variation from normal is the addition of two wires (Shaver Cord) connecting the back of the elbow to a 4 1/4 ounce NICAD battery pack which must be mounted on the prosthesis, the harness, or elsewhere on the body. Recently it has been our practice to mount the battery pack within the prosthesis whenever possible, thus minimizing the amount of external wiring required.

One of the features of the elbow is its quiet operation. This low noise level is made possible by the low-speed motor (6,000 rpm) and the initial worm gear reducer. The remainder of the reduction is obtained by straight spur gears to achieve an overall reduction ratio of 600:1. The model now on the drawing boards includes a safety clutch to avoid breakage if accidental falling should occur and a disconnect to provide a free-swinging elbow when desired. The disconnect for free-swing is operative when the elbow is fully extended and the powered operation reengages when elbow flexion is again selected, following the principle demonstrated in the AMBRL electric elbow.

Different control systems could be utilized, including myoelectric. The present control includes an automatic shut-off at full extension and flexion. Scott s electric limit switches could be used as an alternate method of control and would be especially desirable for nonstandard control systems.

Prof. R. N. Scott, Bio-Engineering Institute, University of New Brunswick, Fredericton, N.B.

Polycentric Knees

By Colin A. McLaurin, P.Eng. Project Director

Two pairs of polycentric knees (Fig. 4 A/B ) have been fitted, one pair to an active boy with bilateral proximal femoral focal deficiency (Fig. 5 ) and the other to a girl with bilateral phocomelia of the lower limbs plus some upper-extremity involvement.

Considerable gait improvement was demonstrated by the boy. With conventional legs he walked with a wide-base waddle and with the new prostheses a narrower base and a more normal gait was achieved. This boy is a very active user and is an ideal candidate for shakedown testing. Some structural modifications have been necessary.

The other user has always been an apprehensive child and gait improvement has not been as marked, but after several weeks of training and experience she has learned to flex the knees of the prostheses when walking. Her previous limbs required strong elastic knee extensors for stability; hence she walked with a stiff-knee gait.

As a temporary measure the limbs have been fitted with polyester laminated shin covers. The possibility of using polyurethane covers from Winnipeg and pre-formed Plastazote* covers is being investigated. The knee mechanism is finished to form a wood block (Fig. 6 ) which can be shaped and laminated like a conventional wood knee.

The Modular Below-Knee Prosthesis

By Gordon Clark Prosthetics Student

Pylon-type prostheses are not used for children as frequently as they are for adults, even though children probably have a greater need for permanently adjustable devices than do fully grown individuals.

Recently we have been experimenting at this Centre with a limb which incorporates a standard SACH foot, a one-inch tubular pylon and a conventional polyester P.T.B. socket with supracondylar suspension. Using Plastazote as a shin cover, the total weight of the prosthesis was 18 ounces (Fig. 7A and Fig. 7B ).

In the fabrication of the cover, one-quarter inch Plastazote was used. It was heated in an oven to 140 degrees centigrade and formed over a wooden mandrel. The ankle flare was shaped after removal from the mandrel and the proximal section was formed to the socket by first heating with a heat gun and then wrapping tightly with an elastic bandage. Because of the white color of the Plastazote, a cotton stocking was pulled over the assembly. However, it is hoped that flesh-colored Plastazote can be obtained for future experiments.

*Polyethylene foam obtained from Smith and Nephew.

The Toronto Standing Brace

By Elizabeth Hamilton, P.T. and Walter M. Motloch, C.O.(C)

In treating patients with spina bifida in recent years, this Centre has concentrated on the pre-school child. It is initiated by a pre-bracing program in a group situation with the parents present. The program seeks to lead these children through the normal motor-development sequence.

The standing brace (Fig. 8 ) is introduced when the child is developmentally ready for standing (age 18 months to three years). Its main function is to provide firm support for unassisted standing and a swing-through gait for locomotion with bars or crutches. This brace provides the child with maximal support, but avoids the expense of providing a finished paraplegic brace. It permits the assessment of the child in the upright position so that it can be determined whether or not he is ready to proceed with formal gait training. The brace is used throughout the day for standing and walking activities and is removed for rest periods and active floor play.

The original standing brace shown in Fig. 8 is stable and easy to fit but since it has no joints the brace must be removed for sitting. A new design, which includes knee joints, is now under development (Fig. 9 ). It consists of a light platform to which standard shoes can be quickly fastened. Two lateral tubular supports extend vertically from the platform and curve inward above the hips to the level of the base of the sternum. Knee supports are attached to each upright tube and a broad webbing band supports the seat. The bars are joined at the apex by a quick-release fastener and with a single motion the sternum pad and the knee support can be swung away and the knee joints released for flexion.

The brace was designed to be worn over clothing so that it can be very easily removed. No attempt is made to hide or disguise its function.

The Coordinated Electric Arm

By Colin A. McLaurin, P.Eng. and Barbara Devitt, O.T.

The coordinated electric arm has been fitted to two children who have bilateral amelia of the upper extremities and normal lower extremities.

One case was an eight-year-old boy who had previously worn and discarded conventional prostheses. The other was a 12-year-old girl who was an excellent user of conventional prostheses.

Since he was fitted with coordinated arms (Fig. 10 ), the boy has discarded them while the girl continues to use hers (Fig. 11 ). Both patients are from out of the Province and neither has returned for assessment so it is difficult to judge the reasons for rejection and acceptance. Before discarding the arms the boy ably demonstrated his ability to perform several functional tasks with the electric limbs, including bimanual activities. He was, however, an excellent user of his feet and had achieved a fair degree of independence without prostheses. The main reasons for rejection appeared to be associated with the restriction of motion imposed by the prostheses, particularly when the boy was participating in games or engaging in rough play. His ability to write and pursue other scholastic activities is considerably better with his feet than with the prostheses. It might well be that when his activities are more formalized he will prefer to wear the prostheses but, in the meantime, no attempt is being made to alter the devices in an effort to improve their acceptability.

The other patient, who had already learned to accept prostheses, was further handicapped with scoliosis which necessitated the application of a Milwaukee brace. In order that the Milwaukee brace could be applied over the prostheses, abduction hinges were added to the shoulder joints. These abduction joints increased the general mobility of the arms and, if properly aligned, do not result in unwanted instability. Proper alignment in this instance means that the plane of the joint should point inwards, i.e., toward the midline of the body (Fig. 12 ).

In the fitting of this particular child, the axis did point inward but not enough. Hence the weight of an object held in the terminal device tended to rotate the arm about the abduction hinge, thus raising the elbow. This problem could also be overcome by the inclusion of friction or a spring in the joint. The abduction hinge has also proved useful in helping the child reach overhead. A unilateral wearer simply powers the arm to bring it behind her back and uses body English to flip the arm overhead where it can be used to reach and operate light switches, etc.

Our bilateral female patient has since been given a Harrington-type spinal fusion and no longer requires a Milwaukee brace. The sockets have been modified by her prosthetist in Milwaukee so that she could wear them over her postsurgical cast. The patient has stated that she prefers electric limbs to her old limbs because they are easier to use. However, several improvements in the prostheses are indicated. The coordinated electric arm was originally designed for a younger child and because of the additional arm length required in fitting this older girl, the forearm force is inadequate. Similarly, the pinch force provided by the three-fingered hooks is not strong enough and the patient has stated that she would prefer to have a conventional two-fingered hook and a wrist rotator.

A Feeding Device For Cerebral Palsy Patients

By Sandra Rife, O.T. and Edgar Kennedy

A feeding device recently developed at this Centre allows many cerebral palsy patients to feed themselves without assistance. The feeder has been designed for those patients who do not have the coordination to use a spoon in the normal way but do have sufficient control of the head to take food from a spoon and sufficient control of the tongue for chewing and swallowing.

The feeding device consists of a plate that can be rotated to select the desired food, and a spoon which scoops up the food and raises it to mouth level. The plate is rotated by pushing on knob A (Fig. 13 ). The spoon is forced down to the plate in a scooping motion by depression of knob B. Depression of knob C releases a catch which allows a spring-loaded damper (door closer) to raise the spoon to mouth level. The spoon is made of plastic to minimize the chances of injury to the mouth.

Only gross arm function is necessary to operate the three knobs and most patients have acquired the necessary skill after brief training. Typically, the feeder can be operated by one arm alone, the knobs being pushed or depressed by hand or fist. Right and left hand models have been produced so that the child may use his most effective arm.

The entire mechanism is mounted on a plastic-covered board fitted with four suction cups to secure it to a table. The plate and plastic spoon can be easily removed for washing.

Acceptance of the device by both patients and parents has been good. A production model, based on a year's experience with various designs, will be available shortly from Sunnybrook Hospital, Prosthetic Services, N. H. and W., 2075 Bayview Avenue, Toronto, Ontario.