An Alternative Myoelectric Prosthetic Fitting: A Case Study

Heather A McKenzie. OT John H Sowerbutts. CP


PATIENT HISTORY

The literature supports that children with multiple limb deficiencies present greater challenges for prosthetic fitting and rehabilitation. In this case study we will present a 3 year old boy, who rejected conventional prosthetic fittings, but was accepting of a prosthetic device which was designed to fit his functional requirements. Jaye is a congenital quadrimembral amputee with a left (L) transverse proximal radial ulnar deficiency. He also has a right longitudinal ulnar deficiency with partial carpels and syndactyly of the second, third and webbed first ray. There are abnormalities at the left (L) elbow joint as well. Function in the left extremity comes from flexion at the radial carpal joint. There is limited extension and supination in this joint.

The diagnosis for the lower extremities is bilateral longitudinal fibular complete with partial tarsals. Jaye experiences staged symes amputations due to investigations to determine the feasibility of toe-to-thumb transfer for the (L) hand. The surgery did not occur and eventually Jaye was fitted with bilateral symes prosthesis by age 2.

At age 6 months, Jaye was fit with a passive arm prosthesis. At age 9 months he rejected this prosthesis when he found that it hindered his movement. He was then fitted with a stubby prosthesis with chest strap which was well accepted.

At age 14 months, Jaye was fit with a "banana-type" prosthesis with an activated 12 p hook and figure 8 harness. He did not accept this prostheses although attempts to encourage him to wear the prosthesis persisted over a 10 month period. Jaye much preferred to use his hands together for fine motor play activities. At age 2, priorities for treatment were focused on lower limb fittings and mobility. Jaye continued to progress in his upper extremity development, finding innovative ways for manipulating objects. He was not, however at all amenable to upper extremity prosthetic training and attempts at further fittings were put on hold. Over the next year Jaye accepted the use of a variety of adaptations for specific activities.

Discussions for refitting the (L) upper extremity with an activated terminal device began when Jaye was aged 3 years 4 months.(Picture 1. )At this time Jaye began attending an integrated preschool program. This program had the services of an Occupational Therapist and individualized assistance in a preschool setting. Mother was very interested, given Jaye's age and placement setting, in attempting the fitting of a myoelectric prosthesis. At this point in time, the clinic team, including the family began problem solving and to look at the factors which had either encouraged Jaye's acceptance or rejection of prosthetic limbs and assistive devices in the past. It was at this time we decided to fit Jaye with a prosthesis which did not conform to the conventional myoelectric fitting.

We determined function to be the most important factor and the family was willing to compromise on the overall cosmetic appearance of the arm to achieve a better functional outcome. To do this, we determined that Jaye needed an arm that would allow him to use both hands together and that anything that hindered that function would result in rejection of the fitting. We decided to keep the prosthesis short, foregoing any type of elbow joint, and to angle the prosthetic hand in towards midline.At this point we conducted myoelectric testing and determined that a one-site, voluntary opening system would be best. Since Jaye did not respond well to a suction socket suspension, an alternative socket was designed. The cosmetic glove was also cut down the wrist area to promote ease of independent positioning of the hand.

Jaye's fitting was complete in Feb'95 and he began wearing the prosthesis 3 times a day for 20 to 30 minutes while working on specific fine motor activities. By the end of February, he had progressed to wearing the prosthesis 2 to 3 hours a day.

At the present time Jaye is using his prosthesis for the majority of his mornings in the preschool setting. The prosthesis is used as an assistive device for bilateral play activities including using scissors. Jaye's acceptance of the prosthesis has been enhanced as well by the use of an opposition post for the (R) hand.

PROSTHETIC DESIGN

After isolating the triceps muscle of Jaye's left arm as an electrode placement site we were able to check controls with an evaluation set up, consisting of a W-0/3 hand from Variety, single site voluntary opening control bridge and a Steeper half size ni-cad battery. The testing went uneventful and Jaye had no difficulty to isolate his triceps muscle and was able to produce a excellent myoelectric signal.

We discussed socket design criteria amongst ourselves an with Mom. it was agreed we should try to fit Jaye with a self suspending socket utilizing his distal residual limb for suspension. Mom was very keen in having him fit with a harness free prosthesis, which would not restrict shoulder motion. We felt that if suspension proved to be inadequate due to weight, then at that time we would consider adding some form of auxiliary suspension, or look at a different socket design. This proved to be one of those cases whereby you really don't know what will work until you try.

It was felt that the less complicated the design, the greater the chance of acceptance, given Jay's previous history of upper extremity prosthetic fittings. Also a socket designed with these considerations in mind would offer a less range of motion.

The casting procedure was straightforward. After establishing proximal trim lines, insulating cream was applied directly over the residual limb. Jaye was a very interested and active participant with lots of questions. We noticed that throughout the entire procedure, his eyes never wandered very far away from what we were doing. The next step was to fabricate a clear plastic check socket from a modified positive mold. From the initial attempt at fitting the check socket it became very apparent that donning and doffing was a very real concern for Jaye. He was convinced that if he got the socket on he would become stuck in it and would not be able to get it off. I tried to convince him that the check socket was just like the cast and that it would come off just as easily as the cast did, however, he did not believe me.

We tried a number of different approaches to get him to try it on; powder; a sheath; mucko/liquid body power; and some T.L.C. from his grandmother.

It was only when we split the check socket and showed him that if necessary we could open it wide enough to allow him to easily slide his arm out that we were able to coax him into trying it on. Once the check socket was on we were able to establish trim lines and electrode placement and to get a feel for whether or not this type of socket design would offer adequate suspension. It was decided that the socket design would have to include some provision for easily doffing the prosthesis and I assured Jaye that it would have this feature. 1 believe that Jaye's acceptance of this device is due in part to the socket design which was a result of his concern about being able to get it off.

The definitive prosthesis consists of a 0/3 Variety hand, a friction wrist, a Bock 13E125 analog electrode. a single site voluntary opening power bridge, a steeper 1/2 size battery box mounted on the medial aspect of the humeral section and a removable anterior sheik held in place with elastic webbing. The unique and ever so important difference from this fitting over a conventional type is the placement of the hand. The wrist and hand are attached to the proximal socket at a 50 degree angle radially to simulate a flexed elbow. (Picture 2. ) This enables Jaye to reach the body-mid-line with ease and makes by-manual task's ever so much more possible. (Picture 3. and Picture 4. )

The anterior shell serves a dual purpose, in that Jaye is assured that there is no way that be can become stuck in the socket and it also aids in suspension by providing pressure over the anterior aspect of the residual limb. This combined with the shape of the distal end is sufficient to hold the prosthesis in place once it is on. Initially, Jaye required some assistance to don and doff the arm, however, he quickly learned to do this himself.

It was not necessary to remove the anterior shell in order to get it on. This could be accomplished by simply sliding the shell distally or rotating it around the prosthesis. Jaye's initial fear of not being able to remove the prosthesis is no longer an issue. All he does now is push and pull to get it on and off. The elastic strap on the shell allows it to move slightly and secures the shell back into its position once the residual limb is completely into the socket.Jaye will have many unique requirements for assistive equipment as he develops. Our goal in attempting this alternative fitting of a j myoelectric prosthesis was to have Jaye accept a prosthesis as a viable option for assisting with specific activities.

We would like to thank the members of the Juvenile Amputee Clinic at the Alberta Children's Hospital specifically Dr. James Harder,MD and Kathi Tedford, PT for their Assistance with this clinical challenge.

Alberta Children's Hospital