NYU Reports On Further Study Of No. 1 (Child's Size) Left Hand

An interim report of the field study of the APRL-Sierra No. 1 Left Hand was recently issued by New York University-Child Prosthetic Studies. Results of the study to date indicated that the hand is generally satisfactory both mechanically and functionally. However, the activity patterns of the young wearers present numerous hazards to hand durability. Rigid quality control in manufacture and assembly and careful installation reduces but does not eliminate the possibility of breakage. Cosmetic gloves available for the hand provide an acceptable appearance. However, although conforming to current manufacturing standards, their durability, discoloration and stain resistance qualities are inadequate for unrestricted hand utilization.1

The report indicates that prescription of the hand may be considered for all unilateral upper-extremity amputation levels from wrist-disarticulation to shoulder-disarticulation within the 4-10 years age range when the normal hand size does not exceed 6 1/4" in circumference at the metacarpal-phalangeal knuckles (excluding thumb) and length (radial styloid to thumb tip) does not exceed 4"; and for both males and females. Because of possible limitations on hand usage related to glove and/or hand durability, concurrent prescription of a hook as a "spare" or "play" device should be routinely considered.

With these qualifications, it was recommended that the No. 1 Left Hand and cosmetic glove be approved for commercial distribution. A background sketch of the history, purposes, procedures and results of the study is presented in the following columns:

Fig. 1 , Fig. 2

History and Purposes

Manufacture of the Left Hand was initiated early in 1961 following the generally successful outcome of the No. 1 Right Hand study. NYU conducted a preliminary examination of two units manufactured by the Sierra Engineering Company, and reported that the hands appeared to be of excellent quality and workmanship. The Subcommittee on Children's Prosthetics Problems authorized the purchase of 55 additional Left Hands for field test purposes.

Two shipments totaling 40 hands were received from the manufacturer but were considered to be unacceptable because of manufacturing deficiencies and all were returned for modification. It was not until February, 1962 that 37 hands were finally accepted for use in the field study. Subsequently, 14 additional hands submitted were found to be acceptable, for a total of 51. During this time, samples of left hand gloves submitted by the Kingsley Manufacturing Company and the Prosthetic Services of San Francisco were examined. The products of both manufacturers were considered satisfactory from the points of view of cosmesis and general workmanship.

The general goals of the study were to: (1) Introduce the hand to the field; (2) Corroborate findings of the laboratory studies; (3) Evaluate the acceptability, utility and application of the production model hand and glove; and (4) Investigate indications and contraindications for prescription.

Three specific aspects of the study were of prime interest: (1) In the evaluation of the Left Hand, functional differences between hook and hand were investigated in greater detail than was the case in the Right Hand study; (2) The short wear life of the cosmetic gloves in the Right Hand study presented a problem. In the course of the prior study the exterior of the hand was extensively modified to eliminate sharp edges which might contribute to glove damage. The efficacy of these charges was of particular interest in the Left Hand study; (3) The effect of hand wear on the child's school behavior was a planned aspect of the Right Hand study. However, little data was obtained on this subject because the study overlapped two school years. With the earlier (February) start of the Left Hand study, these data were to be available for children fitted during February and March.

Results and Child and Parent Reactions

Through October 1962, 39 experimental hands were fitted through 12 of the treatment centers cooperating in the research program (see Table 1 ). Twenty-five children have completed their participation in the study (four months test wear) and have elected to keep the experimental hand, while an additional eleven have worn the hand for a minimum of two months. Two others rejected it after less than two months wear.

The reactions of the subjects and their parents have been strongly although not unanimously favorable to the experimental hand. Of the 25 children (and parents) who elected to retain the hand, 14 decidedly preferred the hand, six preferred the hook, and in five cases a clear-cut pattern was not attainable.

All of the accepting children (and parents) were enthusiastic about the appearance of the item. Opinions concerning function were mixed. Some (8) maintained they could perform more activities with the hand, a slightly greater number (12) preferred the operation of the hook and others (4) said they had no preference while one was too young to answer. Ten parents preferred the operation of the hook, 7 the hand, and 8 expressed no preference. The problem of glove durability, and to a lesser extent that of malfunction of the hand, was a limiting consideration for parents, but was less often of concern to the children, to whom weight and operating forces were more critical.

The two children who rejected the hand were GF, a short below-elbow male amputee, age 4 years and 7 months; and KV, an elbow-disarticulation female amputee, age 9 years and 9 months. GF had previously worn a Dor-rance 10X Hook and Becker Plylite Hand. He was apparently a poor user of his hook, preferring the (lightweight) Becker Hand. According to his parents, the prime reasons for rejecting the hand was that the hook was more functional, easier to operate and held objects better. The boy's teacher said that he was "easily frustrated by failure and very critical of himself." He rejected the hand after two weeks of wear.

KV, a hook user, appeared to like the hand at her initial fitting. The thumb malfunctioned after one day of wear, and the hand was worn two weeks with a malfunctioning thumb. The hand was replaced and worn satisfactorily until the glove became damaged. It was then worn almost two months with a damaged glove, causing the child to be self-conscious. The glove was replaced and the hand worn for three weeks when the control cable broke. KV then withdrew from the study.

To determine the effect (if any) of hand wear on the child's classroom status and behavior, comparable "Teacher Questionnaires" were obtained on 12 children. One set of responses was secured prior to hand fitting and a second after three to four months wear. Time does not permit the analysis of these data and determination of their relationship to the degree of acceptance/rejection of the experimental hand at this writing.

Performance Tests

Considerable attention was given to the identification of functional differences between the hand and hooks previously worn by the subjects. Comparisons of function were made on two bases: (1) Tests scored on the basis of clinical ratings plus performance times; and (2) Child and parent opinions concerning the relative usefulness of the two devices in a wide variety of activities.

Performance tests were given in each of six activities (Kitty in the Kegs, Dry Dishes, Put on Clothes, Loony Links, Cut and Paste, and Eat Ice Cream) at the fitting visit (testing the hook only), and at the two-months visit (testing both hook and the hand). At this writing, test results are available on 34 children.

Within the limitations of the data, it appeared that: (1) Based on average performance ratings and times, the hand was not superior to the previously worn hook in the performance of any one of the six activities; and (2) In neither ratings nor time was the difference between hook and hand performance very great. Furthermore, in each of the six activities a small number of children were rated as performing better with the hand than with the hook and many did as well with the hand as with the hook.

Hand Durability

Reported malfunctions have occurred in 15 hands worn by the children during the field study. Examination of 14 of these hands indicates that the majority had more than one defect. The incidence of malfunction within the relatively brief period of the study (four months wear or less), is cause for concern.

In some instances, the causes of breakage were beyond the manufacturer's control, e.g., falls, foreign matter entering the hand, and inadequate installation. In other cases, deficiencies in hand design, materials or workmanship appeared at least contributory to the malfunctions. Areas in which manufacturing improvement might be effected are: (1) Staking of the thumb pivot pin; (2) The manufacture, installation and, perhaps, design of the thumb operating mechanism; and (3) A stronger control cable (and a simpler method of installation so that broken cables could be replaced in the field).

Gloves-Cosmetic Acceptability

The cosmetic gloves utilized in the field study were considered to be adequate in regard to appearance and workmanship. The reactions of children and their parents to the color, texture and length of the glove were overwhelmingly positive (at the time of delivery). At the four months visit, of the 25 children (and parents) completing the study and retaining the hand, one parent and one child rated color as unsatisfactory because it did not match the child's present sun tan. All parents and children regarded the texture as satisfactory.

Durability of Gloves

The gloves emerged as a major problem, however, because of their lack of durability. The 25 children who completed their four months visit at this writing have averaged 1.7 months of wear per glove. On some gloves the first holes appeared after only a week's wear. Three children wore one glove throughout the study and 11 used only two gloves. Two children have had five gloves.

The crux of the problem, obviously, is that the No. 1 Hand population (primarily 4-8 year olds) lead very active lives and that many of their activities, particularly in play, constitute a major hazard to cosmetic gloves (and to mechanical hands). To alleviate the problem, some of the parents limited use of the hand to less hazardous occasions (school and social), but limitation of use is not the most desirable solution. A major effort to increase glove durability is indicated. Two considerations are involved:

  1. Improvement of glove materials; and

  2. Softening the exterior of the hand.

A final report on the No. 1 Right and Left Hand studies, including analyses of the "Teacher Questionnaires" and "Performance Tests", will be issued by New York University in the near future and will be published in a forthcoming issue of Artificial Limbs.

Work continues at the Army Prosthetics Research Laboratory on plastic formulations designed to provide improvement in these characteristics.