Built-in Wrist Flexion for Children's Prostheses

Susan Clarke, O.T.R. Carole Krai, O.T.R. Julie Shaperman, M.A., O.T.R.

This work supported by Grant C-199 (C-1) and Grant 12: HS Project 204. Children's Bureau, Department of Health, Education, and Welfare.

The child with a bilateral upper-extremity loss wearing conventional prostheses can often benefit from wrist flexion. The higher the amputation level, the less ability the child has to compensate for his anatomical loss by substitute motions. Wrist flexion can also be useful to children fitted unilaterally, especially for the child who wears a prosthesis on one side and needs to reach a phocomelic extremity on the other.

The addition of wrist flexion to the conventional upper-extremity prosthesis allows the child to:

  • Bring his arms close to his body for self-care activities

  • Bring arms together for bimanual activities

  • Use his arms to perform these activities with less body bending and exertion than would otherwise be necessary.


In the experience of personnel at the Child Amputee Prosthetics Project at the University of California, Los Angeles, commercially available wrist-flexion units** did not prove to be satisfactory for children because they: added terminal weight; were an added component for the child to pre-position; and were mechanically unreliable.

For these reasons another method of obtaining wrist flexion was sought. In a 1962 test, an adult, bilateral, above-elbow amputee who wore wrist-flexion units agreed to keep his wrists fully flexed for a two-week period. He reported that he could easily perform all needed activities, including those required by his job, without changing the position of the wrist-flexion units. Following this, a child with similar amputations was fitted with experimental wrist-flexion units which could be locked in any selected position of flexion. A trial period of several months in various positions of flexion showed that the child could perform any needed activity with the wrists flexed.

As a result of these tests it was suggested that the conventional wrist unit be laminated into the forearm of the prosthesis in a flexed position. Before fitting the first patient in this way, an evaluation was done to determine the most advantageous angle for the "built-in" flexion. The evaluation indicated that the degree of flexion needed might vary for each patient. It was also noted that, in addition to flexion, some radial deviation (angulation above the horizontal plane) was needed for the first patient (Fig. 1 ).

Since 1965, 16 patients have worn prostheses with built-in wrist flexion provided by laminating wrist units into the forearm at a specified angle (Chart 1 ). All 16 accepted the built-in flexion feature and found it functionally beneficial. Selection of patients to receive built-in wrist flexion and selection of the flexion angle to be used are determined by the extent of involvement of the upper extremities, and by functional need. The evaluations are done by the occupational therapist and prosthetist and include observation of function in the child's work area, and his reach to the opposite extremity and to parts of the body as needed for self-care. Factors unique to each patient are given special consideration.

Case Histories

Case I

S. L. is a 13-year-old female with bilateral, standard, above-elbow amputations, a right partial foot, and a left standard below-knee amputation. She has been fitted with bilateral, standard, above-elbow prostheses since she was four years of age. She also wears lower-extremity prostheses.

S. L. was originally considered for built-in wrist flexion at the age of nine years. Her prosthetic skills were excellent and she was well motivated to be as independent as possible. An evaluation was made to determine the possible benefits and problems that would be presented by built-in flexion. Commercial wrist-flexion units were added to both prostheses. On the first day the units were set at 25 deg. of flexion and S. L. was told to leave them in that position all day. In an evaluation of activities of daily living, the occupational therapist found that the wrist-flexion feature improved the patient's ability to don and remove her panties and cleanse her perineal area. S. L. was also better able to perform activities such as buckling her belt, brushing her teeth, and eating, which required working close to her body at waist and mouth levels.

On the second day the wrist units were set at 50 deg. of flexion. There did not appear to be any improvement in skills beyond those seen with the wrists in 25 deg. of flexion, and it was more difficult for S. L. to don and remove her sweater and jacket. After this initial evaluation both the patient and her mother reported that when the wrists were flexed to 25 deg. there was a definite improvement in function and at no time did the flexion feature present a functional problem.

Therefore, new forearms with wrist units set in 25 deg. of flexion were prescribed (Fig. 2 ). After receiving these forearms, the child's functional skills improved as was expected from the previous evaluation. Increased independence in toileting and dressing skills was especially noticeable. Built-in flexion did present one problem. S. L. had difficulty in firmly grasping the handlebars of her bicycle. Her father solved the problem by altering the angle of the bars.

Since her initial tilting with built-in flexion, S. L.'s skills have continued to improve. She has had two new pairs of prostheses with built-in wrist flexion since the original set. In both instances 25 deg. of flexion was provided. She is currently independent in self-care except for fastening her bra. and in putting on stockings, an activity which is complicated by her lower-extremity prostheses. She attends high school and follows a normal curriculum.

Case 2

S. G. is a 10-year-old girl with bilateral shoulder-disarticulation amputations and a right proximal femoral focal deficiency. She received her first pair of shoulder-disarticulation prostheses at two and-a-half years of age and by four-and-a-half years of age was a skillful prostheses user and full-day wearer. In 1966. when a number of patients had already been fitted with built-in wrist flexion, it was decided to determine whether this type of modification would be of value to S. G. Testing was carried out in a manner similar to that described for Case I (S. L.). i.e., by locking the hooks in 25 deg. of wrist flexion and evaluating the results. In addition, the units were placed in 15 deg. of angulation upward to simulate radial deviation. With the hooks in this position, S. G. was able to reach her mouth, face, waist, and perineum more effectively. It was also found that she had a better view of small objects such as pencils or crayons in her hooks; and that she could see her writing more easily.

Subsequently, S. G. has had her prostheses replaced twice because of growth and each pair has had the wrist units set in 25 deg. of flexion and 15 deg. of radial deviation (Fig. 3 ). She attends regular school and participates in all activities except field sports. She still requires some assistance with her clothing when toileting herself.

At this patient's last occupational therapy evaluation, the value of her flexed wrists was again discussed. S. G. is currently quite happy with her present limbs. However, the therapist feels that the radial deviation on the non-dominant side does not add to her function as the dominant prosthesis is used for eating and desk skills for which the deviation is an asset. The deviation

does seem to make it more difficult to stabilize objects on a table and, therefore, the possibility of eliminating the radial deviation on the nondominant side is being considered.

Case 3

This six-year-10-month-old boy has congenital anomalies of all four limbs: left upper-extremity amelia, right upper-extremity phoeomelia, and bilateral clubfeet. D. B. ambulates independently. The right upper extremity consists of a single-boned shaft slightly longer than elbow length. On the distal portion a flexible joint resembling a rudimentary wrist terminates in a two-fingered hand. Strength and skill in using the two digits has increased with functional use. Because of the lack of an elbow joint, however, the working area for bimanual activities is limited.

Fitting the boy with a passive left shoulder-disarticulation-type prosthesis at the age of 13 months was unsuccessful because the prosthesis interfered with his attempts to walk. At 22 months of age, D. B. was fitted with a standard shoulder-disarticulation prosthesis on the left with thigh-control harnessing.

Evaluation by the occupational therapist revealed that the position of the prosthetic forearm was unsatisfactory. The boy could not bring his hook and phoeomelic extremity close enough together to perform bimanual activities adequately and transfer of objects between hand and hook was difficult.

At the age of three years, two months, D. B. received a new longer forearm with the wrist set in 40 deg. of flexion and 25 deg. of radial deviation. This arrangement placed the hook closer to his body and in closer proximity to the phoeomelic hand. This relationship increased his work area and facilitated the performance of two-handed activities. D. B. wore this prosthesis for three-and-one-half years with one socket change required because of growth.

At six years, 10 months of age, D. B. received his third prosthesis, a left standard shoulder-disarticulation type. In this prosthesis, wrist flexion was reduced to 25 deg. and radial deviation was eliminated. With the previous prosthesis he had had difficulty in stabilizing objects on the table with his hook. His phocomelic arm had grown and could be brought close to the hook without need for deviation in the prosthesis (Fig. 4 and Fig. 5 ). Initial evaluation showed that the working area between the phocomelic extremity and the prosthesis was adequate with 25 deg. of wrist flexion. The elimination of radial deviation seemed to facilitate the stabilization of paper and other objects on a table.

Future evaluation will be done when D. B. enters the second grade in a school for handicapped children where he will receive weekly occupational therapy. If function in school skills and toileting improves sufficiently, it is hoped that D. B. will be able to transfer to a regular school within the next two to three years (Fig. 6 ).

Case 4

M. N., a nine-year, three-month-old boy, has bilateral upper-extremity phocomelia with three digits on the right limb and two on the left. He is able to use the digits of his right hand to hold a spoon for eating and to grasp various other lightweight objects. With his left phocomelic extremity, he holds very small lightweight objects after someone has placed them in his hand. He is unable to manage bimanual activities without a prosthesis.

When M. N. was three years of age, bilateral fitting was attempted using shoulder-disarticulation-type prostheses with openings for the phocomelic hands. These prostheses were rejected as the child was more independent without them, both at home and at school. They were advantageous only for swinging on swings, catching a ball, and carrying trays. M. N.'s right phocomelic extremity provided him with considerable function, but on the left he lacked the firm grasp and reach necessary to perform most activities.

At four years of age, M. N. was fitted on the left side with a prosthesis of the same type as was tried earlier, with the elbow lock operated by the phocomelic hand. The prosthesis provided him with reach and some limited bilateral activity as was expected. Problems encountered included difficulty in reaching the hook with his phoeomelic hand and in positioning it for bimanual activities. In order for him to perform bimanually, the prosthetic forearm had to be flexed to 125 deg., which made hook opening difficult.

Subsequently, M. N. has been re-fitted twice on the left side with prostheses similar to the one described above. Each of these prostheses had a short humeral section and longer forearm section so that M. N. could reach the hook with his phocomelic hand without flexing the prosthetic forearm as much as formerly. Each of these prostheses also had the wrist set in 25 deg. of flexion (Fig. 7 ). This angulation brought the hook closer to the body and to the right phoeomelic extremity. Thus he could place objects into the hook more easily and perform some midline activities such as zipping and unzipping trousers for independent toileting. In future prescriptions, consideration will be given to adding 15 to 20 deg. of radial deviation at the wrist so that M. N. will be able to reach his phoeomelic hand without flexing his prosthetic elbow beyond 90 deg. (Terminal device operation is difficult when the elbow is flexed past 90 deg., because of slack in the cable.)

M. N. attends a school for handicapped children where he is doing third-grade work. He uses his prosthesis primarily for desk skills and other school activities. Due to poor motivation and lack of parental support for his prosthetic program, improvement in dressing skills has been slow.


Built-in wrist flexion assists in the performance of self-care activities and is not a disadvantage in performing other activities. The flexion lessens the amount of exaggerated body motion needed for activities such as eating.

When a functional evaluation has determined that there is a need for flexion, patient acceptance of built-in flexion has been excellent. Patients who have worn prostheses with wrist units set in flexion request that this feature be included in subsequent prostheses.

Mechanical reliability and low cost are two additional advantages of placing the wrist unit in the flexed position. There does not appear to be any unusual stress on the wrist unit placed in this position, and fabrication time is not affected since the forearm can be ordered from the commercial manufacturer with the wrist unit laminated at the desired angle at only a slightly increased cost, which is less than that of a commercial wrist unit with positionable flexion.

The amount of wrist flexion needed by individual children varies, although most seem to find 25 deg. or less a comfortable and useful position. There appears to be no advantage to built-in wrist flexion beyond 25 deg.

Radial deviation is of value to some children. It appears most useful on the dominant side and is most advantageous in self-care activities performed at the midline of the body. On the nondominant side it is needed only in selected cases as it may interfere with stabilizing or weighting objects on a table surface. The child using a prosthesis in conjunction with a phoeomelic extremity may find radial deviation useful since it tilts the hook upward toward the short phoeomelic hand.

Objective methods to determine the amount of flexion needed by individual children require further development.

Methods for determining which children would benefit from radial deviation, and at what angle radial deviation is most effective, require further study.

**After this evaluation started Hosmer Inc. developed a new component for wrist flexion which provided more reliable function and a decrease in weight as compared to previous models. To date we have not had any experience with this unit.

Susan Clarke, O.T.R., Carole Krai, O.T.R. and Julie Shaperman, M.A., O.T.R. are associated with the The Child Amputee Prosthetics Project University of California Los Angeles, California