The United Kingdom Trial of the Swedish Myoelectric Hand for Young Children: An Interim Report

H. J. B. DAY, M.R.C.S., L.R.C.P.


Immediately following a demonstration in London of the Swedish miniature myoelectric hand, the Department of Health and Social Security decided to undertake a trial in the United Kingdom. The need for a trial was based on the fact that the hand, which had become commercially available in 1977, had not been evaluated outside Scandinavia, where it had been fitted to only 25 to 30 children. A team consisting of a research prosthetist, two engineers, and the author visited the Regional Hospital, Orebro, in April 1978, to discuss with Dr. Sorbye and the manufacturers of the hand their experience and the criteria which might be used in selecting children for the trial.

The Swedish results indicated that success was most likely to be obtained in children aged between 3 1/2 and 4 1/2 years with a level of loss in the middle third of the forearm, and it was decided to use these basic conditions in the United Kingdom trial. A study was made of the clinical records of all arm-deficient children attending Artificial Limb and Appliance Centres in England and Wales who were born between 1st February 1974 and 31st March 1975. After exclusion of those patients whose level of loss was obviously wrong, a list of 28 names was compiled, and these children were invited to attend for formal assessment at Roehampton or Manchester, depending on their place of domicile.

In addition to a normal clinical examination, a myotester was used to establish the ability of the child to produce adequate signals, and a Social Worker interviewed the parents to provide base data on the family. Of the 28 children evaluated, five were rejected because their level of loss was considerably lower than the junction of middle and lower thirds of the forearm. All 23 children accepted for the trial had previously worn conventional prostheses, and 13 were established split-hook users. Patient Catagories Chart

Fitting Programme

The first fitting took place in August 1978, and fittings continued at the rate of one child every two weeks at each of the two Centres, the last child being fitted on 26th February 1979. The procedure adopted has been for the child to attend for casting and measurement and to return after one week for a trial fitting of the socket with the electrodes in position and the hand fitted to a temporary arm. The forearm is fabricated, and the arm is assembled ready for delivery seven days later; and following this the mother and child have remained at the Centre for a week's initial training by the Occupational Therapists. Follow-up attendances are at four-week to eight-week intervals.

Clinical Evaluation

In order to introduce some objectivity into what is essentially a subjective assessment, two measures were introduced.

  1. An electronic device is incorporated into each prosthesis to count the number of hand operations.
  2. A set of standard functional tests was devised by the Occupational Therapists concerned, to be performed at the end of the first week's training and on every subsequent follow-up visit.

Interim Results

At this stage (April 1979) it is far too early to come to any definite conclusion, but some general statements can be made.

  1. All the children could produce adequate myoelectric potentials, and the location of the optimum position for the electrodes presented no problem.
  2. All the children were able to produce hand movements very quickly. The ability to control the hand purposefully is achieved only after practise and training.
  3. Most found the prosthesis heavy in the first few days but quickly became accustomed to this weight, and we do not consider the weight to be a problem.
  4. Most of the parents like the prosthesis, but a few have been disappointed because their child's performance did not match their expectations. This problem may result from the enormous publicity the device received.
  5. Children and parents value the absence of harness, although the battery lead can be troublesome.
  6. Of the 21 children who have had the prosthesis for more than three months, three showed signs of wishing to revert to the split hook for at least some activities. Of the remainder, 18 wear the prosthesis all day and every day, five appear to derive some real functional benefit, and 13 use it some with encouragement but usually do little more than is possible with a passive hand, for example, cycling.
  7. Our experience with the electronic counter is not long enough to be very helpful and has been affected by the hand repair rate (vide infra). Counts range between 500 and 3500 per day.
  8. The functional testing demonstrates the progress of the particular child but is not of great use in comparing children with each other.
  9. There is no significant difference in the rate of learning of the functional ability achieved between those children who formerly used a split hook and those previously fitted with only a cosmetic hand.
  10. Many of the children have experienced difficulties arising from the frequent occurrence of faults. In order to minimise the time a child would be without his prosthesis, we instituted a policy of repair by replacement. This practise has achieved its primary object but has uncovered a particular problem: the geometry of the grip between thumb, index finger, and middle finger is not identical in all hands, and this lack of consistency tends to retard the child's progress.

Technical Evaluation

Full records have been kept of repairs and defects. Initially the repair frequency was high, and many of these repairs were concerned with design limitation or deficiencies of assembly of the hand. Close liaison with the manufacturers has resolved some of these problems, and the repair rate has fallen but remains too high. Average Repair Frequency Chart

Interim Conclusions

  1. Our experience is short. Twenty-three children have been wearing this prosthesis for periods ranging from two to nine months. It appears that they accept this type of prosthesis well, although the majority use it mainly in a "dynamic cosmetic mode." A minority (perhaps 25 per cent) appear to gain functional benefit, but a further 15 per cent who were good hook users show signs of rejecting the myoelectric hand.
  2. Any firm conclusions will be reached only after a longer period, since the crucial factor will be the extent to which these children find the myoelectric prosthesis satisfactory in the long term. The normal process of growing up and developing skills and interests which require fine, accurate manipulation will play a part in their decision.
  3. Although the reliability of the equipment has improved, the repair frequency is still too high to be acceptable in normal service conditions.

References:

 

    1. Sorbye, R., Myoelectric controlled hand prostheses in children. Int J Rehab Res, 1 (0.1977) 15-25.

 

  1. Communication with the author reveals that in the year following the presentation of this paper a total of about 50 children have been fitted with the Swedish Hand, and a follow-up of the original group is continuing--Ed.