O&P Library > Artificial Limbs > 1972, Vol 16, Num 1 > pp. 20 - 50

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The Child with Terminal Transverse Partial Hemimelia: A Review of the Literature on Prosthetic Management

Barbara L. Sypniewski *

Introduction

This independent-study honors project dealt with congenital skeletal limb deficiencies. This paper discusses and reviews the literature concerning the prosthetic management of the individual with unilateral terminal transverse partial hemimelia of the upper extremity. Specific topics considered are: a general description of the entity, including etiology and incidence; psychological factors affecting the limb-deficient child and his parents; normal and abnormal biomechanics of the upper extremity; components of the prosthesis (terminal devices, wrist units, elbow hinges, cuffs, harnessing, and sockets); prosthetic prescription and fitting; the trend toward early fitting; preprosthetic therapy; and prosthetic training. One section discusses the information elicited from a survey conducted by letters and questionnaires that were sent to the 28 clinics participating in the Child Prosthetics Research Program, conducted under the auspices of the Subcommittee on Child Prosthetics Problems of the Committee on Prosthetics Research and Development to ascertain the age of the congenitally skeletally limb-deficient child at the time of his initial fitting for a prosthesis. An analysis of the data from the 12 clinics replying is presented, along with the developmental criteria for fitting.

The scope of this paper is limited to the unilateral upper-extremity, below-elbow congenital amputee. Bilateral amputees, cineplasty, surgical conversion, or externally powered prostheses are not considered. The literature review was limited by time to the books and journals published in 1960 or later, with selected earlier articles. Articles published before 1960, as well as those not available at the Albany Medical College Library or through the inter-library loan system, are listed in the "Bibliography." Both reference lists were compiled from Index Medicus; Amputees, Amputations, and Artificial Limbs (published by the Committee on Pros-thetic-Orthotic Education of the National Academy of Sciences-National Research Council, Washington, D.C.); and the bibliographies of articles I reviewed.

Terminal transverse hemimelia indicates congenital absence of the entire distal part of the limb below the elbow. The term is part of the modified Frantz-O'Rahilly classification nomenclature. Hemimelia is the absence of a large part of a limb, from the Greek melos meaning limb and hemi, half. Partial hemimelia indicates that less than half the limb is missing. The defect we are considering is transverse rather than longitudinal, presenting a short or very short stump similar to that of an acquired below-elbow amputation.

The etiology of skeletal limb deficiencies is largely unknown, except for the well-documented teratogenic effects of thalidomide. The thalidomide tragedy has led to an increased interest in, and awareness of, what can be done for the congenital amputee.

The list of proposed etiological factors includes environmental conditions such as drugs, maternal health and nutrition, genetic factors or predisposition, and chromosomal aberrations. Most congenital defects have their origin during the first eight weeks of embryonic life.

Glessner indicates that there are two distinct groups of congenital absence of limbs: (1) spontaneous intrauterine amputation after limb formation, caused by focal deficiencies, and (2) limb-bud arrests or agenesis of the terminal part of the limb. Amniotic bands wrapped tightly around part of an extremity may lead to necrosis and eventual intrauterine amputation. Terminal deficiencies due to limb-bud arrests are by far the most common type of congenital absence. The terms congenital amputation and congenital skeletal limb deficiency are used interchangeably in the literature.

Terminal transverse partial hemimelia is the most common type of congenital limb deficiency. There is unexplained preponderance of left-sided absence (2 or 3 to 1), and females are involved more frequently than males. Studies by Bergholtz, Davies, Friz, and Clippinger, Munson and Dolan, and Gehant failed to show the greater incidence in females exhibited in Kay and Fishman's report.

The measures of prosthetic management in habilitation of a congenital amputee are somewhat different than those employed in the rehabilitation of an "acquired" amputee. The child must learn functional skills that he never possessed, rather than relearning substitute functional activities. The fact that the juvenile amputee is neither skeletally nor emotionally mature is an important consideration in the prosthetic management. The growth and development of the limb-deficient child is essentially the same as that of the normal child; the environmental stimuli to motor development are not decreased significantly by unilateral deficiency. Ideally, prosthetic management should extend from birth through vocational training.

Function of the upper extremity is extremely complex and relatively independent of the contralateral extremity. With unilateral absence, there is an increased use of the remaining extremity, since the ability of a prosthesis to compensate for the loss of an arm is significantly less than is possible in the lower extremities. Below-elbow amputees are least in need of externally powered prostheses. They can effectively use body power to activate the prosthesis and receive the benefits of sensory feedback through the socket and harness. The prosthesis should be considered as an assistive device in bimanual activity. Because absence of one extremity can be easily compensated for, getting the unilateral amputee to use his prosthesis presents a great challenge. Fitting and training should be started as early as possible, before these compensations can develop.

It is generally believed that a team approach is most successful in the management of the limb-deficient child. The foremost members are the mother, who spends the most time with her child and influences him the most, and the child. Other possible members of this interdisciplinary team are the physician, orthopedist, prosthetist, occupational therapist, physical therapist, psychologist, social worker, and biomedical engineer. Each child presents unique problems to be met. Epps and Brennecke outlined a sequence of treatment that includes referral, history and medical examination, intake evaluation, preprosthetic physical and occupational therapy, prescription, fabrication, thorough check-out by the team, training, and regular recheck every three or four months.

Factors influencing the cost of the prosthesis are: age at initial fitting, regular maintenance, frequency of harness adjustment, wearing pattern, operating skill, acceptance, and components prescribed.Average service for a prosthesis ranges from two to three years, but a child fitted during infancy may require three to five prostheses before school age. The additional cost of early fitting is compensated for over the years, especially in regard to the benefits of skill and acceptance.

Psychological Aspects

The importance of parental attitudes towards the child, his disability, and the idea of a prosthesis, and their effect on the eventual acceptance or rejection of a prosthesis, has been emphasized throughout the literature. There is no direct correlation between the degree of the child's deficiency and the mother's perception of the child's abnormality, her feelings toward him and the way she handles him. The way in which parents deal with the birth of a limb-deficient child depends to a great degree on how they have coped with previous crises. Replacement of a missing extremity with a well-functioning artificial one is valuable only if the parents can accept the idea of a prosthesis. Often, children have rejected prostheses because the parents, consciously or unconsciously, could not accept the fact that it was necessary.

The way in which the parents are informed of the child's deficiency may influence their later reactions. If he desires to do so, the father should be allowed to inform the mother, in the presence of a physician. Mothers can be profoundly influenced by the reactions of the delivery-room staff. The training of the limb-deficient child can best begin by providing the parents with a detailed, factual, realistic, and sympathetic appraisal of their baby and his prospects for future educational, vocational, and social rehabilitation. Unrealistic claims that modern prosthetics and engineering can provide artificial devices as natural-looking and as efficient as the human hand can seriously hinder the habilitation program. The first few hours after the birth of the child are crucial; it is during this period that parents form attitudes and defenses that can have tremendously far-reaching effects.

With the birth of a deformed child, the parents suffer a severe psychological shock, for which they are totally unprepared. Certain emotions have been commonly expressed by parents of congenital amputees: guilt, hopelessness, death wishes, fear, anger, rejection, despair, shame, repulsion, grief, shock, hostility, and abandonment. The need for prompt, professional assistance is crucial.

Parents are extremely sensitive to the reactions and attitudes of others, and they need help to know that they and their child are accepted. In addition to individual counseling by a psychologist, social worker, or other qualified persons, group sessions have been established. Parents benefit from the opportunity to verbalize their feelings and receive support and help in handling their emotions and in developing constructive attitudes. Wallace noted the impact of these group-therapy sessions on the fathers, citing fewer absences, less hesitation about expressing their feelings, and awareness that their attitudes affect the child's adjustment and help to mold his self-image.

If, instead of realistic acceptance, strong defense mechanisms are built up by the parents during this early period, they will not be able to communicate with their child when he becomes aware of and questions his deficiency. One indication of the mother's acceptance of the child is the way she handles the baby. Some important factors to look for in observing parental behavior are: avoidance of direct contact with the baby, ritualistic organization and emphasis on cleanliness, barriers to communication, aggression toward professionals, and subconscious refusal to accept the existence of the child's abnormality. The mother will eventually become the child's best therapist, and the early months must provide a basis for her later role. Parents must be aware of the importance of their love in the future rehabilitation of their child. Hall and Mongeau and others advocate that children become an integral part of the family immediately. Mongeau found that children taken home directly from the hospital after birth have shown greater capacity for adaptation than those who were institutionalized. A strong family basis can be of great help to the child when he may later face repeated hospitalizations for prosthetic training or other reasons. According to Gesell and Amatruda, a child's basic behavior traits are fairly well established by the time he is a year old. Some of these traits are hereditary and some are absorbed from the attitudes of the family.

Crisis intervention, as described by Brooks and others, is the awareness of impending crises in the development of the limb-deficient child and the intervention by qualified professional personnel to aid in making those transitory periods as easy as possible. One such crisis is that of homecoming. The curiosity and concern of relatives and friends must be faced. The effect of the birth of a limb-deficient child naturally has a great impact on his siblings. They too must be aided in adjusting to this stress situation. Other potential crisis periods are prosthetic fitting, entering school, and adolescence. During the child's period of growth and development, he has the same needs for independence and self-sufficiency that normal children have. Dependence and overprotection must be avoided. Discipline must be consistent and realistic, neither extremely permissive nor extremely restrictive. The profound effects of the parents on the child cannot be overemphasized.

The manner and degree to which the child is influenced by his deficiency is determined before he reaches conscious awareness of his condition. If he has been provided with a sense of security, acceptance, and love, he will have a strong basis from which he can develop a positive self-image and achieve independence. The limb-deficient child faces the same problems and sequence in emotional and social development as normal children, but each crisis is likely to be of greater intensity and magnitude. The child who has received encouragement and support from his family will expect the same type of relationship from outsiders and will approach social contacts spontaneously, rather than attempting to avoid them. The child will attain a balance between the dominance of his parents' influence and the satisfaction he gains from his independence. He should be encouraged to enter into social relationships with a minimum of special attention.

Taylor has discussed at length the psychological needs of handicapped children. In addition to the fundamental needs of love and acceptance, she cites the needs for adventure and exploration, rebellion to release pent-up frustration, limitation of freedom, friends and social experience, privacy, achievement as a basis of self-esteem, and the need for awareness of the child as a person. These needs are the same as those operating in all nonhandi-capped individuals.

Gouin-Decarie recognized that a pertinent problem in studying the psychology of a limb-deficient child relates to his conception of space, which is closely associated with the formation of the body image. She found that these children made use of a visual, rather than a tactile, image in recognizing familiar objects. Several authors have discussed the concept of body image, or schema, in child amputees. All have indicated the absence of marked distortion of body image in most of these individuals. Alteration of body image is, however, a significant problem in noncongenital amputees. Centers and Centers analyzed the results of a draw-a-person test administered to congenital amputees. The majority of amputees represented themselves realistically, either leaving out the missing limb or including the prosthesis. They concluded that, while body images differed in a matter-of-fact way, they did not differ markedly in signs of greater conflict, anxiety, or defensiveness. The study did not support the authors' hypothesis that amputee children will have more conflict and defensiveness about their bodies than will nonamputee children.

The body image is critical in relation to the acceptance or rejection of a prosthesis. Congenital amputees experience the same processes in the formation of body image as normal children. The earlier the child is trained to wear a prosthesis, the easier it will become a part of his body image. One factor in the ready incorporation of the prosthesis is that modern prostheses are functionally adequate for many of the activities engaged in by young children. A prosthetic device is never really useful until it is integrated into the body schema. Acceptance and rejection of the prosthesis is more extensively considered in the section on early fitting.

The question of the possibility of the phenomenon of phantom sensation in congenital amputees is an interesting one. A discussion of the theories concerning the cause of this phenomenon is beyond the scope of this paper. Hoover, Lambert, and Simmel believe that neither phantom-limb sensation nor pain exists in this group of individuals. Lambert bases his belief on the principle that nerve endings going to the distal limb have never developed. Simmel attributes the impossibility of phantom sensation to the fact that the absent part has never been represented in the body schema. In their census of the juvenile-amputee population, Kay and Fishman reported three instances of phantoms in congenital amputees, but these could not be substantiated by further interrogation. Weinstein and Sersen reported phantoms in 5 out of 30 children with congenital deficiencies. If the presence of a phantom reflects the "need" of the child to experience a missing part, it should have functional properties. The phantoms reported in this study were usually shrunken, telescoped parts with gaps and missing appendages.

Certain other psychological aspects can best be discussed as they relate to the chronological age groups of the congenital amputee. The significant divisions are: preschool, entry into school, latency, and adolescence.

In the preschool category, a period of negativism and resistance occurs around two years of age. This is a normal reaction; the child is trying to establish his personality and achieve a little independence. This period of negativism often conflicts with prosthetic-training procedures, especially terminal-device activation.

Entry into school is an important milestone for any child. He moves from the security of his home environment into a competitive social society. The limb-deficient child needs a reliable basis for dealing with this new group of people. This is provided by his parents and family during the early childhood years. In his group experience, the child will test and validate ways of dealing with people outside his family . Adjustment is facilitated if the teacher and class are prepared and informed in advance. Healthy curiosity is the most frequent reaction of classmates, and a factual explanation of the prosthesis and its use should lead to acceptance by the classmates and increased self-confidence of the limb-deficient child. Wilson expresses the belief that it is preferable for the limb-deficient child to attend regular school. Unnecessary special consideration should be avoided. The handicapped child may experience feelings of social devaluation, which any member of a minority group feels. Centers and Centers discuss the results of a social-discrimination questionnaire. The hypothesis that peer-group children express more covert rejecting attitudes toward amputees than toward nonamputee children was supported. They attribute this finding to the fact that one of the most significant variables operating in social interaction is personal appearance. Centers and Centers conducted their study almost ten years ago. It would be interesting to retest this hypothesis in light of recent social trends toward greater acceptance of minority groups and increased emphasis on individual merit as opposed to sterotyped generalizations.

The preadolescent latency period is relatively calm, with no major crisis periods. The normal child experiences many conflicts during adolescence, many of which are associated with appearance. These conflicts are all compounded in the limb-deficient child. During this period, a cosmetic hand is often prescribed for the adolescent amputee to replace the functional hook for social occasions. Vocational guidance becomes increasingly important during this period of adolescence.

Normal and Abnormal Biomechanics

The arm enables the hand to be placed in position for skilled functional activities. The most commonly recognized forms of prehension include tip, palmar, three-jawed-chuck, lateral, hook grasp, cylindrical grasp, and spherical grasp. Palmar prehension employing opposition of the thumb predominates in picking up objects and holding them for use. Long tendons with muscles at a distance permit the great variety of motion characteristic of the human hand. In addition to skill, the hand frequently functions in support postures. Sensation is another major function of the hand. The hand is richly supplied with sensory-nerve endings mediating touch, temperature, pain, and position. Large areas of the cerebral cortex represent the complex sensory and motor function of the hand. Boivin advocates investigation into the prehension patterns and sequences commonly used in activities of daily living. Stabilization of the wrist in various positions aids prehension. For example, the wrist assumes an angle of 145° when very strong prehension is required. Finley, Wirta, and Cody studied the synergic action of muscles of the upper extremity resulting in a better understanding of the relationship between central and peripheral control of movement. The three major components of the response phenomenon that they noted were: cognitive, ballistic-type physical displacement, and apparent sensing to compare, confirm, or adjust to assure successful accomplishment of the desired act. The information regarding time sequences is useful as reference material in studying pathomechanics.

Finger and hand movement, wrist flexion and extension, and varying degrees of pronation and supination are lacking in the congenital below-elbow amputee. Prosthetic replacement of the wrist and hand is poor, only crude prehension and positioning are possible, and there is no substitution for the lack of sensory feedback. Maximum utilization of the residual biomechanics is essential in prosthetic replacement. The biggest challenge is to design an upper-extremity prosthesis that (1) can be powered by and controlled with little effort, (2) can perform through the almost spherical range of a normal arm, (3) has a terminal device that can achieve prehension, (4) will respond to sensation, and (5) is cosmetically acceptable. Upper-extremity prosthetics are significantly deficient in all of these areas. Because of the fixed prehension pattern of the terminal device and the fixed wrist, nearly all fine orientation movements must be made at levels higher than the forearm by compensatory motions of the elbow, hand, and shoulder . Prosthetic controls permit only the simplest motions decomposed into their basic elements and executed slowly, in series, one at a time.

Stoner notes that no prosthesis accomplishes any of the wrist-flexion movements. The reasons for this neglect of wrist replacement are: (1) usually no controls from the harness are available to furnish the power, (2) wrist motions are used in fine movement of the hand and are not essential to bring the hand into the major spheres of action about the body, and (3) loss of wrist flexion can be compensated for grossly by other arm motions. Preposition flexion devices are available and are useful for activity close to the body.

Pronation and supination are functions of forearm length. Wrist joints allow passive positioning for the most advantageous angle of terminal-device operation. With shorter forearm stumps, the mechanical advantage of flexion is decreased, in addition to the loss of pronation and supination.

Joint motions in congenital amputees are often bizarre. Kruger and Breyan report that, in an X-ray evaluation of 16 extremities with terminal transverse partial hemimelia, 13 showed dislocation of the head of the radius. Of these, 77% showed dislocation before prescription of the initial prosthesis. It is therefore concluded that the phenomenon is inherent in the disability itself. The dislocation is asymptomatic. The authors offer two possible explanations for the phenomenon: deficiency of the ligamentous structures, or unopposed action of the biceps brach-ialis muscle. They consider the latter explanation the more likely. In short stumps, the pronator teres muscle is absent, and the biceps in flexing and supinating meets no opposition, thereby dislocating the radial head.

Harnessing

Harnessing techniques for upper-extremity prostheses must be based on bio-mechanical analyses of the remaining movements. Successful use of the prosthesis requires a harness that allows the most efficient use of those movements that are available. The socket limits some of the residual motion of the stump itself, and the harness limits the motion of the sound extremity to some extent. The harness should distribute the weight of the prosthesis evenly over a wide area and be functional in as many positions of normal use as possible. It should transmit power with a minimum of interference and be operable by relatively inconspicuous body motions. Power is provided by the stump itself (elbow flexion) or by the relative motion between two body parts (glenohumeral flexion and/or scapular abduction). Control-cable systems transmit this power from the amputee's body to the prosthesis. The suspension system may use a figure-of-eight, figure-of-nine, or shoulder-saddle chest-strap type of harness. The most common suspension is a figure-of-eight harness with a Northwestern ring-type cross. The Northwestern ring allows adjustment of individual harness straps. The figure-of-nine harness is often used for power transmission with Munster-type sockets, which do not require a great deal of additional suspension. The chest strap is useful in spreading the load in heavy work and maintaining the prosthesis in the proper position in the presence of baby fat. The harness provides some degree of feedback from the environment. O'Shea has described a shoulder-saddle chest-strap harness with the primary advantage of increased comfort. Hile described the adaptation and reinforcement of a brassiere to replace the chest-strap harness when breast development occurred.

Requirements for suspension and harnessing vary from individual to individual, and skillful use of the available power sources is essential to good prosthetic use. Rapid rate of growth and limited power are critical factors in designing harnesses for congenital amputees. Frequent adjustment by the prosthetist assures optimum harness and prosthetic function.

Components of the Prosthesis

Terminal Devices

Two major considerations in the design of a prosthesis for a child are the continual neuromuscular and skeletal changes due to growth and the child's limited sources for power and control. Linear growth is more rapid than circumferential growth. The prosthesis can be fabricated to allow for later adjustments for growth, thus extending the functional life of the device. The components must be sturdy enough to withstand vigorous use, yet must be light enough to be controlled by the child. Some of the problems involved in the prosthetic replacement of human body parts are control, feedback, reliability, size, and appearance. Upper-extremity prostheses for children are essentially scaled-down models of adult types. However, Hall and Wilson note that recent advances in children's prosthetics include improved design and function of terminal devices, lightweight plastic sockets and shells, and more efficient harnessing methods. There are a large number of mechanical components available that can be combined to best meet the needs of the individual child. Split mechanical hooks stress the restoration of function at the expense of abnormal appearance, while artificial hands with cosmetic gloves attempt to combine modest levels of function with near-normal static appearance. Both hooks and artificial hands should be given the same care as the normal hand; since sensation is absent, they are more prone to damage.

There are two mechanisms of terminal-device operation: voluntary opening and voluntary closing. In the voluntary-opening type, tension on the control cable opens against a variable spring force, while in the voluntary-closing type, control-cable tension closes against the spring force. Hooks and hands are available with either mechanism. Voluntary opening is the simplest form of prehension mechanism: the prehension force is provided by special heavy rubber bands. Among the disadvantages of this type are the inability to handle delicate or heavy objects, and the fact that this mechanism is opposite to the prehension of the normal hand. An advantage of the voluntary-closing terminal device is that it more accurately simulates normal prehension, and pressure can more easily be graded to the object to be grasped. Formerly, manually controlled locks were employed, but now automatic locking is available. The fact that, to release the lock, the cable pull must be greater than the pull that closes the terminal device may be a disadvantage. Neither mechanism has been proved superior in a wide range of activities, but research to improve both types for juvenile amputees is continuing.

Ritter and Sammons have elaborated on the advantages of voluntary-closing devices for children's prostheses. The fact that normal prehension is simulated is especially relevant in bilateral grasping. Performing different hand patterns simultaneously, as is necessary with voluntary-opening devices, is particularly difficult for the preschool child to learn, since he is still developing refinement of prehension. A description of the Army Prosthetics Research Laboratories (APRL) voluntary-closing hand, which provides palmar prehension of the three-jaw-chuck type, has been presented by Stoner. Teska and Swinyard have described a test to evaluate its functional capacity, versatility, and durability. Research is also being conducted concerning the Robins-Aid voluntary-opening hand. The concept of cosmesis, or the appearance of the prosthesis, is difficult to define, but is very important. It is a very individualized concept, having varying importance for different people. Function, cosmesis, and acceptance are almost inextricably allied. The area of compromise between function and cosmesis is a delicate and crucial one. Those professionals vitally concerned with function must be careful not to look down on the parents who may seem to be overly concerned with cosmesis. Several new plastics have been reported that, while not identical to the color and texture of the human skin, do convey an idea of softness and warmth. These new terminal-device designs represent an attempt to combine improved function with an aesthetically satisfactory appearance, but without trying to imitate representationally the characteristics of the missing part.

It was formerly common practice to provide the congenital amputee with a plastic mitt or wafer as the initial terminal device. Dean, Lineberger, and Watkins and Ford have presented arguments supporting this practice. Among the major reasons given are: cosmetic appeal, flexibility, support without slipping in creeping, avoidance of injury to the child himself or others during play, and other factors supporting early fitting in general.

The infant passive hook is now considered the better choice as an initial terminal device. Some of the reasons for its preferred function are listed by Blakeslee: (1) it provides for gross palmar prehension and body-support activities with skill equal to the mitt, (2) it allows the infant to hook over objects for support in pulling to a standing position, (3) it provides a holder for small objects that are placed in it, (4) it helps the infant to develop bilateral prehensile awareness, being recognized as a device to hold objects, and (5) parents who were willing to accept a prosthesis for their child readily accepted the passive hook. Shaperman reported the results of an evaluation of the passive mitt and the passive hook with similar results. She also noted improved skill and increased speed of learning when the control cable was added to the passive hook. Initially, the hook presented a slightly greater safety hazard, but the injuries that did occur were minor. Shaperman noted that the hook was one ounce heavier than the mitt, but it appeared to be well within the limits of the infant's ability to lift and manipulate it easily.

Hooks are available in a variety of sizes, shapes, and weights. The Dorrance 12P or 10P hook are commonly provided for the unilateral juvenile amputee. They are canted and plastic-covered. Proponents of prescribing hooks cite the advantages of greater prehensile function, with greater visibility and facility available. Numerous authors have expressed a preference for the use of the hook rather than the hand. Edelstein maintains that the cosmetic appeal of a skillfully used hook is greater than that of a cadaverous-looking glove. The idea that the hook can only be accepted as a tool, and that therefore it is hard to see the need for a more cosmetic socket, has been expressed by Boivin . Research toward improved hook design and function is being carried out. The literature reveals progress reports in the development of the Sumida hook, the Northwestern University Center control hook, the Steeper split hook no. 65, and other more recent advances in prosthetics. Carroll conducted a study to analyze the prehension force needed by child amputees. The test items were related to function and varied with the age of the child. Most items tested static prehension only; the individual could either hold the object, or it slipped out of the hook because of insufficient prehension force. Dynamic prehension, or the child's ability to control the prehension force, was tested by the ability to hold a paper cup with water in it. The results of this study showed that more children were fitted adequately in regard to the size of the terminal device than in relation to the prehension force. None of the children were found to be wearing an excessive number of rubber bands. With the exception of the toddler group, the prehension force was found to be inadequate for performance of one or more of the test items. One result of this study was a set of suggested pinch forces for below-elbow amputees:

Greater consideration needs to be given to the adequacy of prehension forces for the functional activities of congenital amputees.

Cosmetic hands are often prescribed when the juvenile amputee reaches adolescence. Interlocking wrist-unit mechanisms are available that permit the use of a hook for functional activities and a more cosmetic hand for social occasions. These hands usually provide a modified three-jaw-chuck prehension between movable index and middle fingers and a thumb that can lock in position. Hands available for children include the Dorrance no. 2 hand and the APRL-Sierra child-size no. 1 hand. One disadvantage that must be considered is the greater weight of the hand as compared to the hook. The APRL-Sierra no. 1 hand weighs 170 grams, while the Dorrance 10x hook weighs 60 grams. This is especially important, considering that this additional weight has the mechanical advantage of a long forearm lever and the congenital amputee does not possess a great deal of muscle power.

The APRL-Sierra no. 1 hand was developed to meet the need for a functional and cosmetically acceptable hand for juvenile amputees. It is a voluntary-opening mechanism with a hand shell of cast aluminum, articulated index and middle fingers, a two-position thumb, and nonarticulated but flexible ring and little fingers. In this field study, only 7 of 77 children rejected the hand completely. The remaining participants fell into four groups: those that used the hand exclusively, those that used the hand predominantly, those that used both equally, and those that used the hook predominantly. The authors suggest that the age of the child is a major factor regarding hook or hand preference. Younger children may experience difficulty with hand weight and opening forces, may be more careless in their use of the hand, and may be less subject to social pressures toward cosme-sis. Sex appeared to be an even greater consideration than age. Girls of all ages appear to be potentially the best candidates for the Sierra-APRL no. 1 hand, while younger boys would seem least likely to accept the device. Fishman and Kay performed a study to delineate the relative usefulness of the hook and the hand. The results were at variance with previous clinical impressions, which indicate that a hand is a significantly less functional terminal device than a hook. In an extensive evaluation of the Dorrance no. 2 hand in 72 bimanual activities, Gorton found that no definite trends emerged to indicate that the hook was measurably more functional than the hand or that the hand was significantly more functional. The test employed by Fish-man and Kay analyzed general and specific patterns of grasp by means of functional activities. The rating scale for performance of activities was somewhat subjective, but the detailed analysis of the results was excellent. From this study, the authors concluded that: (1) the APRL-Sierra no. 1 hand was heavier and, in most cases, more difficult to operate than the previously used hook, but these were not serious drawbacks for the majority of subjects; and (2) the hand provided somewhat less pinch force than most of the hooks and a less precise grasp. While the majority of children reported that they could perform more activities better with the hook, they also were able to specify a number of activities that were performed better with the hand, such as picking up a pencil, grasping paper, and holding silverware for eating.

Constant research and re-evaluation of prostheses is