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Transition to a Switch-Activated, 3-S, Transhumeral Prosthesis: A Team Approach

Kris M. Vacek, OTD

ABSTRACT

This article discusses the upper extremity prosthetic treatment of a 13-year-old young man with right hemiparesis and mild learning difficulties. Past prosthetic devices offered little independent function because the strength and energy required to operate the prosthesis was too overwhelming for him. With his new prosthesis, he has gained more independent function, cosmesis, and comfort. Accompanied by an upper extremity rehabilitation program, this prosthesis allows the patient increased independence and function in his daily activities at home and school. The importance of a structured program from an occupational therapist is vital to the success of this prosthesis. This is a case report where an experienced upper extremity prosthetic team successfully fit a patient who never functionally used a prosthesis until the age of 13.

Key Words: Upper Extremity Prosthetics; Above Elbow Amputees; Transhumeral Amputee; Switch-Activated Prosthesis; 3-S for UE Limb Loss.

Introduction

Approximately 40,000 people lose a limb every year in the United States. Thirty percent of those involve the upper extremity, and 3% of those are born with a congenital limb absence. It is estimated that 50% of upper extremity amputees choose to wear a prosthesis.¹ Despite these overwhelming statistics, only a small number of healthcare providers have extensive knowledge and experience in dealing with upper extremity prosthetic rehabilitation. This is a case report in which an experienced upper extremity prosthetic team successfully fit a patient who had never functionally used his prosthesis until the age of 13. The team included the prosthetist, occupational therapist, patient, family members, and school staff.

Review of the Literature

There are generally three categories of prosthetic options for the upper extremity amputee currently available. They include a passive, cosmetic prosthesis; a cable-driven, body-powered prosthesis; and an externally powered, electrically controlled prosthesis by either myoelectric sensors or specialized switches.² However, the reality is that there is no perfect replacement for the human hand. Therefore, it is imperative to determine which options will benefit patients and meet their individual needs.

A prosthesis is unable to provide the amount of function, reliability, sensory feedback, and cosmesis the human hand naturally provides. Therefore, it is vitally important for the healthcare provider to possess knowledge of the various options continually being developed to ensure satisfaction for the patient. Since the percentage of upper extremity amputees who actually wear a prosthesis is 50%, the prosthetic rehabilitation team needs to focus goals around the individual's needs and desires. The goal is to obtain the maximal level of independence possible to ensure that the amputee achieves success with his prosthesis. Development of the prosthesis, education, training, and follow-up are all implemented by the team members.² As stated in the literature, "a well-rounded rehabilitation program is equally as important as a well-fitting prosthesis. The quality of training will determine how the individual uses the prosthesis for the rest of his or her life." ³

Parents often blame themselves when their child is born with a congenital limb absence. Research indicates there is often no direct cause for a congenital limb absence.⁴ This knowledge is important to convey to parents who may feel responsible. It is also important for parents and family members to realize that their feelings and opinions about the prosthesis may eventually affect the child. "Clear correlations exist between the child's motivation and the parent's opinion concerning usefulness and cosmesis of the prosthesis."⁵ For the pediatric amputee, the parents are the most important members of the upper extremity prosthetic rehabilitation team, especially in promoting satisfaction and functional use of their child's new prosthesis.

The following case report describes how a 13-year-old young man with right-sided hemiparesis and mild learning difficulties was successfully fit with a prosthesis utilizing a switch-activated, silicone suction socket (3-S) design, an automatic forearm balancer (AFB) elbow, and an Otto Bock terminal device. The prosthesis currently allows him to perform several activities he was unable to complete with his previous cable-driven, body-powered prosthesis. He uses his prosthesis to help with primary functional activities, such as carrying his school lunch tray, opening containers, and typing on the computer. Further clarification will be provided explaining how the team approach was successful in determining the type of prosthesis, providing training for its use, and educating the family and school staff to ensure carry over for this individual to achieve improved independence at home, in school, and during play.

Case Report

Patients with neurological damage present with a variety of deficits. This patient (RW) presents with moderate right-sided hemiparesis and mild learning difficulties. Additionally, he has a congenital loss of his left arm at the transhumeral level. These deficits are secondary to congenital and neurological genesis. This combination of deficits has always limited his ability to successfully operate a cable-driven, body-powered prosthesis. His mother reports making him wear it to school, hoping the prosthesis would help him with his school activities. School time became the only time he wore his prosthesis. RW reports that the prosthesis did not help increase his success with daily activities. RW reports that he would remove the prosthesis as soon as he came home from school. The strength and energy required to operate the elbow and to work the terminal device were always too overwhelming for him.

RW was born two weeks premature. He suffered two separate cerebrovascular accidents (CVA) during labor and delivery, possibly secondary to anoxia. It was apparent his right side had been affected from the CVAs as stiffness and lack of voluntary movement were immediately apparent. RW additionally demonstrated a left congenital limb loss through the transhumeral aspect of the arm. The effect of the neurological damage was not yet apparent. Doctors predicted RW would be moderately mentally disabled. RW began to achieve developmental milestones slower than average, but he continued to advance despite what doctors had predicted. Currently, RW is labeled as demonstrating mild learning difficulties.

Occupational therapy was initiated at six months of age to promote appropriate development of his muscles and integration of reflexes. He received his first prosthesis at 10 months. His prosthetist recommended the passive prosthesis be on at all times, except during sleep or while bathing. His family reports being inconsistent with his wearing schedule, possibly due to their attitude and feelings about the entire situation of having a child with limb loss and doubt about the wearing benefits. They state he wore it 25% of his waking time despite their knowledge of its benefits. According to Hubbard,⁵ providing a passive prosthesis in early infancy assists in balance, terminal length awareness, and gross motor development. Additionally, "benefits of early fitting include better acceptance of the prosthesis by the child, the parents, and the community; improved functional outcome; normal development of bilateral patterns of upper limb function; and optimal integration of the prosthesis into the body image during development."⁶

At age two, RW received his first functional prosthesis. It was cable-operated with a figure eight harness securing the prosthesis to his body. It had a functional elbow and a 12P hook. During RW's initial fitting, it was apparent to his family and prosthetist that, despite his limited cognition, it was his lack of sufficient body power that diminished his ability to functionally operate the elbow and terminal device. Thus, various harness strategies were introduced to find one that would allow maximal function and minimal excursion. The chest-style harness worked best by allowing some immediate function; RW could learn to utilize chest expansion as well as bi-scapular movement to operate the elbow and terminal device.

RW's mother recalls that several healthcare workers, including physicians, prosthetists, physical therapists, and occupational therapists, were involved in her son's care. As she remembers, only one out of several occupational therapists stood out as possessing knowledge and skill in prosthetic training. This therapist helped RW maximize use of his current prosthesis by focusing attention on his weak right side, which fatigued quickly and was limited in range of motion and strength. Despite the progress made in occupational therapy, his wearing schedule continued to be limited because he lacked enough body power to use his prosthesis all day.

Additional areas of focus in occupational therapy included his right upper extremity, unilateral independence, and activities of daily living (ADL). RW never showed much progress with his right upper extremity. With his right hand, he was, and continues to be, unable to open containers, grasp firmly, or carry objects. He essentially needs to wear his prosthesis to assist with these activities and additional ADLs to achieve some independence; yet, difficulty remained with the cable-operated prosthesis since he was not an "all-day" functional wearer.

RW's mother reports feeling fortunate to have had an OT who possessed prosthetic knowledge. On the average, occupational therapy students traditionally receive minimal exposure to upper extremity prosthetic training techniques. Often it includes a brief introduction to the available components and how they are operated and cared for, and therapeutic techniques are touched on, but not elaborated on. With this in mind, it is imperative that an upper extremity prosthetist work closely with an occupational therapist in order to ensure that necessary follow-up is provided.

As he grew, use of the prosthesis did not get easier. The strength and energy required to operate the hook were overwhelming for him. The prosthesis offered little function for him. His right side was not strong enough to raise the elbow and operate the terminal device functionally. Throughout the day, he complained of tingling under his right arm. These problems are all characteristics inherent in a conventional prosthesis, especially when the uninvolved side is affected in some way.⁷ By age six, RW began to express that he was unable to control the prosthesis out to his side, down by his feet, or above his head. This limited range of motion is a characteristic of a body-powered prosthesis.⁷ In an area outside the frontal work envelope, his body was unable to provide enough gross body movement to generate adequate excursion of the cable, which pulls open the terminal device. RW eventually came to a point where he no longer wore the prosthesis. Without his prosthesis, he required assistance with most activities due to his weak right side.

The Prosthesis

It was not until the age of 13 that a prosthetist specializing in the upper extremity offered hope to RW and made a recommendation. RW required a prosthesis offering increased ability to function independently without excessive fatigue. The prosthesis needed to be comfortable and aesthetically pleasing. The prosthetist recommended an externally controlled prosthesis no longer controlled by a cable and cosmetically similar to his contralateral hand and forearm, potentially offering him increased function, cosmesis, and comfort.

RW was fit with a prosthesis utilizing a harness pull switch,b 3-S socket design, AFB elbow,b and an Otto Bock cosmetic terminal device.b He currently wears his prosthesis all day from the time he wakes to the time he goes to sleep. His occupational therapist has worked with him on a prosthetic training program to assist RW in learning to control the prosthesis since it is different from what he had been used to. The prosthetist and occupational therapist have worked closely with his school staff and family, educating them on the features of the prosthesis to ensure the consistency that RW needs to increase his independence with the new prosthesis.

This new prosthesis has resulted in increased comfort, improved function, and expanded wearing time. RW was freed from tight harnessing; although, a harness is still present. He was able to complete tasks he could not complete before, such as carrying his school lunch tray, opening and closing containers, and typing on the computer using his right hand in conjunction with his prosthesis.

Prosthetic Features

For RW, the harness pull switch was incorporated in a cable control, figure eight harness and used for control of the system's electric hand. Tension in the harness activates the switch to release control signals, which are transmitted by cable.⁸ The prosthetic team has found the switch-activated prosthesis to be especially beneficial to people with affected sound limbs or humeral muscle weakness. It has been concluded that the switch-activated prosthesis requires approximately two pounds of excursion to operate the terminal device. Comparing this to the cable-operated, body-powered prosthesis, which uses approximately six pounds of excursion per hook rubber, proves a big difference since the average wearer has four to six hook rubbers on at a time.

RW's cognition did not limit his ability when learning the operation of the switch control. The switch-controlled prosthesis is operated in the same line of pull for opening and closing. A firm pull on the switch connected to the harness opens the terminal device, and a lighter pull closes the terminal device. Two clicks of the switch are heard for opening, then, after relaxing, one click is heard to close the terminal device. The prosthetist and OT were present the day of delivery. The OT worked with RW in operating the functions of the prosthesis. RW had no trouble catching on to the workings of his new prosthesis. He had practically mastered operation of the terminal device that day.

In the past, RW never was satisfied with the fit of his socket. He often complained of discomfort and a poor fit. The distal end of his stump is sensitive due to bony overgrowth. He has had surgical procedures to modify his stump. "Bony overgrowth is a condition seen only in child amputees where the limb deficiency or amputation is through the long bone (both congenital and acquired) before they reach skeletal maturity." Setoguchi reports initially the overgrowth appears as a small bursa, then evolves into a bone spur. As the spur grows, the pain increases. He also reports bone overgrowth commonly does not occur in the humerus.⁴ For RW, the growth did occur in his humerus. As a result of his episodes with distal end sensitivity, the 3-S socket was utilized.

The silicone suction socket uses a sleeve made of silicone that intimately fits the residual limb. This provides a suction type of suspension for the extremity.⁹ "Silicone's adhesive nature is advantageous because the material never rotates, shifts, or displaces when properly fit to the residuum."¹⁰ The result is a primarily self-suspending prosthesis eliminating cumbersome harnessing. 3-S success is ensured when certain criteria are met: "(1) mid to long humeral amputation, (2) minimal scar tissue, (3) unilateral amputation, (4) minimal retraction of muscles when the biceps or triceps is contracted, and (5) stable volume."¹¹ In RW's case, he was a good candidate for the 3-S system. Success has been demonstrated especially with the elimination of tight harnessing. He no longer complains of tingling or sensation loss in his right side. Additionally, operation of the terminal device outside the frontal work envelope is achieved successfully.

The AFB elbow is operated by a spring-loaded cable connected to the harness. In RW's case, he chose to eliminate this cable since he infrequently used it. He prefers to manually flex the elbow by stabilizing the forearm on a table or his knee, then locking the elbow using his right hand to pull the lock mechanism. The locking mechanism was modified so he could grasp it easily. Later, the elbow cable can easily be reinstalled if he desires to use it.

A loose-fitting harness triggers the switch that operates the hand's open and close mechanism. The hand is similar to his right hand cosmetically. The wrist rotates manually and can be rotated by placing the hand between the legs and twisting the arm. RW's right hand function limited him from operating the standard toggle switch to turn the hand on and off. His prosthetist modified it so the switch was located in the forearm shell where he was able to operate it using his right hand.

Successful prosthetic use requires independence in donning and doffing of the prosthesis. RW has demonstrated independence with this by using his right hand to assist while stabilizing on a table. Currently, RW independently turns the prosthesis on and off, rotates the wrist, and manages the battery. These skills did not come naturally; however, with occupational therapy, he learned to master them.

Occupational Therapy

Fabrication and delivery of a prosthesis do not ensure success. In this case, development of this prosthesis was centered on the needs of the individual patient. The next phase, according to Atkins,² in guaranteeing success is educating the patient and continual follow-up with the patient. This is a time when family support and specific training is very important. Crone⁷ stated it the following way: "It is generally agreed that the acceptance of a myoelectric prosthesis, like acceptance of a standard prosthesis, is dependent on psychological, socioeconomic, and occupational factors as well as on the technical perfection of the prosthesis and adequate training and follow-up."

The goal of prosthetic training is to assist the child in learning how to incorporate the use of the prosthesis in normal everyday activity. Hubbard⁵ asserts the following: "Skill acquisition, however, is a long-term process and requires a cooperative effort by the child, family, school, and therapist. It is not enough to simply apply a prosthesis and expect that the child will magically become two-handed."

The prosthetist and occupational therapist of the prosthetic team met at RW's school to provide the necessary instruction. The teachers, students, school occupational therapist, and RW's mother attended. After a demonstration of the workings of the prosthesis, the teacher and occupational therapist proceeded to identify specific tasks in the classroom that RW had demonstrated trouble with. Together, they worked to find solutions that made independence possible. Through this collaborative effort, several problems were solved, and family and school representatives were present to ensure carryover. Additionally, the two occupational therapists established a treatment plan together that the school occupational therapist planned to continue.

The school staff found this visit extremely beneficial since they initially felt very intimidated and uncomfortable about working with the prosthesis. They reported being afraid of breaking it. They did not understand how it worked. Some skills the school staff learned and found beneficial were how to rotate the wrist, how to turn the prosthesis on and off, and how the elbow locks. These were all simple operational issues that, once addressed, made the school staff feel more comfortable. After the instruction, they reported being excited about working with RW in prosthetic training.

The school occupational therapist continued to consult often with the team's prosthetist and occupational therapist. She found benefits in having their support and knowing they could be utilized as a resource when questions arose. Specific occupational therapy tasks that RW benefited from focused on the mechanical operations of the prosthesis. The occupational therapist worked with RW on wrist rotation, turning it on and off, and locking the elbow. She has worked on functional skills that are specific to RW's everyday living, such as opening and closing containers and dressing himself, including fastening. Among the skills learned in therapy were positioning of the terminal device for such activities as typing and holding paper while writing. He has learned how to carry his school lunch tray and how to position the elbow and lock it for various tasks. Working with the school occupational therapist was beneficial because she has helped identify and solve problems that perhaps the teacher or family did not see. For example, the occupational therapist thought of modifying the elbow locking pull switch so RW could independently use his right hand for independent operation.

Since the school OT had not been exposed to prosthetics before in practice, she found it beneficial to have direction from the team OT. Occupational therapists, however, are very qualified to work in the area of upper extremity prosthetics because of the core classes required in occupational therapy's curriculum. Classes including anatomy, physiology, kinesiology, neuroanatomy, and physical rehabilitation techniques provide a solid foundation for understanding the dynamics of a prosthesis. Additionally, classes including psychosocial theory and practice, human development, cultural awareness, and in-depth knowledge of occupation provide a solid foundation for therapeutic interaction with the many psychological factors commonly accompanying amputations.

An occupational therapist's primary focus is to enable the client to become as independent as possible in the activities most important to them and that are vital to everyday living. Additionally, an occupational therapist can be reimbursed for his or her time and a prosthetist cannot. The teamwork of a prosthetist and an occupational therapist is not only beneficial to the patient, but cost-effective. An occupational therapist can relieve a prosthetist from unbillable training time he or she may spend and free the prosthetist to focus on the fabrication and modification of the prosthesis. The occupational therapists can be responsible for providing many necessary pre-prosthetic or post-prosthetic training technique opportunities.

Discussion

The past decade has seen many changes in rehabilitation's available technology. Through improvements in reliability and the design and development of prosthetic components, it is now possible to fit prosthetic devices for the pediatric population at any age.⁵ Yet, as Berbrayer asserts, "to achieve success, the amputee should have intact cognition, a supportive family or attendant care system, and access to a specialized amputee facility."¹² In the case of RW, the patient demonstrated positive family support but his cognition had been a concern. However, he proved he had the drive to learn how to manipulate the prosthesis independently and safely.

Conclusion

For 13 years, RW strained with a prosthesis that was too cumbersome for his right side to operate. The prosthetic team felt he would function more independently with something that required less excursion to operate. They felt he demonstrated adequate cognitive ability to utilize a switch-operated prosthesis. A switch-controlled prosthesis was successfully fabricated and fit to the patient. RW now tolerates wearing and using his prosthesis all day. He reports increased ability to complete activities he was unable to complete with his old cable-operated, body- powered prosthesis. Additional correspondence with the school occupational therapist and his family aided with problem solving and ensured consistency. Through this interaction between the prosthetic team and his school therapist, teacher, and mother, their uncertainty about the unfamiliar has been eliminated. The hope of the prosthetist is that this hybrid system will be used as a transitioning prosthesis from his previously worn cable-driven, body-powered prosthesis to a myoelectric, externally powered prosthesis.

References:

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