Chapter 34B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Upper-Limb Deficiencies: Prosthetic and Orthotic Management
Terry Supan, A.A.S., C.P.O.
The function and design principles of prostheses for children are similar to their adult counterparts. Whether the child has an acquired amputation or a congenital anomaly, our goal should be to provide the most functional and cosmetic design possible when and if the rehabilitation team and the family decide that the child should be fitted with a prosthesis. The key difference is that children's prostheses must also be developmentally appropriate.
Age guidelines for optimum fitting have changed as we have gained more experience. No longer must we wait until the teenage years to fit a myoelectric prosthesis. Nor do we wait until the child has lived a year before fitting after tumor surgery. Traumatic amputees now receive their first prosthesis in a matter of days, not months.
During the 1980s, a plethora of new components, materials, and techniques were developed for the adult or geriatric amputee. A specific attempt was made at the end of the decade to redirect this effort toward the pediatric patient. Myoelectric hands, elbows, and controls were miniaturized and simplified (Fig 34B-1.). The lighter-weight, stronger new materials could be used for children. Thermoplastic socket designs allowed for more adjustability and adaptability for growing limbs. Redesigned lower-limb components also became available for the younger amputee.
In a break with the past, the U.S. government did not underwrite this developmental cost. This resulted in increased costs as the manufacturers amortized research expenses. Although we are fortunate that some entrepreneurs have been willing to invest in such a small area as upper-limb prosthetics, the substantial cost for newer technology is an ongoing concern.
The modularization of upper-limb components during this period offers the potential to recycle parts into the child's next prosthesis. The preschool amputee may need a new socket annually because of growth, but the expensive myoelectric hands and electronics should be reusable in the new prosthesis, provided that the size remains appropriate.
The development of simplified myoelectric control and a battery-saver circuit allows the fitting of infants with a practical control scheme. While hand opening and thumb adduction usually begin around 4 months, the development of shoulder-hand coordination is delayed until after 9 months. Because of training difficulties, cable-controlled prehension of the prosthesis is seldom feasible until 12 to 18 months. The new myoelectric circuits provide controlled opening, automatic closing when the child relaxes, and a stall condition detector to save battery capacity automatically. This type of prosthesis is easier for the infant to learn to use because any electromyographic (EMG) signal detected within the socket creates hand opening. As the child develops normal coordination of the contralateral hand, he also spontaneously improves his prosthetic function.
WHEN TO FIT AND WITH WHAT
The key questions are when a child should be provided with a prosthesis and what the best type is. There are no simple answers. "How soon?" is probably best answered by "when technically possible." The child with a traumatic or acquired amputation should ideally be fitted within 30 days (Fig 34B-2.) to encourage acceptance of the prosthesis and the continuation of bimanual activities. The child with a congenital condition may be provided with a passive hand within 60 to 90 days after birth. This theoretically allows the child to acquire more normal bimanual and quadripedal development.
"What type of prosthesis?" is much more difficult to answer. The well-informed prosthetist can guide the physician through this ever-changing area of new terms, techniques, and technology. "Should powered or mechanical components be used?" "Both" is the best answer to that question. Each has its own advantages and disadvantages, and they can often be used in combination.
Multiple prostheses with differing control patterns, however, can lead to confusion and frustration. Therefore, only one type of prosthesis should be used for the very young child. As children mature, they should be given the opportunity to experiment with different
Mechanical terminal devices are lighter, have fingertip prehension, and are less susceptible to damage. Unfortunately, voluntary-opening hooks have much less pinch force than do electric hands and are not as cosmetic. Voluntary-closing devices like the Adept have a graded pinch force that is controlled by the individual. The streamlined design of hook devices permits visual inspection of the objects to be grasped, which can be advantageous.
A myoelectric hand has greater pinch force and is capable of controlled opening and closing throughout the full range of motion of the arm. It also can be operated independently of elbow function. However, it cannot be submerged in water, is heavier, and is not as adept at picking up smaller items. The cosmetic gloves must be replaced routinely to prevent moisture and dirt from entering the electrical and mechanical parts.
Passive, mechanical, and electric elbows are all available for the child amputee. Like the terminal devices, each has advantages and disadvantages. Weight and function are the best guidelines to use when recommending elbow components.
Passive elbows are light but must be operated by the other hand. Heavy-duty use would preclude the use of a passive elbow.
Cable-controlled mechanical elbows are smaller versions of the adult models. One cable controls elbow flexion, and the second controls the locking mechanism. The child must learn more complicated shoulder motions to achieve both flexion and locking of the prosthetic elbow, which is sometimes difficult.
When a mechanical terminal device is used, the elbow must be locked for the cable's force to be transferred to the hook. However, if a myoelectric hand is used with the cable elbow, then terminal device and elbow function are independent.
Electric elbows for children are usually switch controlled, but myoelectric controls are available for the older youth. They are heavier, more costly, and more complicated but are easier for the patient to control because they require less force, excursion, and coordination. They are often used with short residual limbs or congenital limb remnants.
The acquired unilateral amputee should be fitted with the most cosmetic, functional components available. Children over 3 years of age can be trained to control all available devices. Younger patients or those with congenitally deficient limbs sometimes do not have sufficient neuromuscular control to operate complex devices. Although the fitting of a single-function myoelectric terminal device for infants is controversial, the 6- to 9-month-old can spontaneously develop control of the prosthesis without extensive training. Whether they will continue to use the prosthesis or reject it later in life can only be determined by a longitudinal study. It can be argued that fitting the child, despite the uncertainty of future results, will stimulate further advances in the science of prosthetics. Reliability of electric prostheses has improved significantly and will continue to do so as long as we continue fitting such devices.
RECOMMENDATIONS BY LEVEL
Infants with partial-hand amputations or congenital deficiencies probably would be best served by not fitting them with a prosthesis. Children with unilateral conditions will readily adapt to their "one-handedness," with the noninvolved side becoming the dominate hand. There is a lack of functional prostheses for the young child with only digits or metacarpals missing. The available cosmetic partial-hand prostheses compromise the sensory feedback to the limbs inside the prostheses. Combining this with an increase in length usually results in a rejection of the prosthesis.
Transverse anomalies or amputations can be provided with an orthosis to prevent deformities or increase prehension. Although attempts at fitting opposition posts and platforms can be made, long-term use of these for the unilateral patient has been inconsistent (Fig 34B-3.). More effort should be concentrated on adaptability without the use of prostheses or orthoses. The exception would be the child who has a limb-length discrepancy that would allow the fitting of a functional prosthesis of equal length to their sound side. Then the recommendation would be to give the family the option to fit the infant with a prosthesis when possible (Fig 34B-4.). This would allow the prosthesis to become part of the child's natural development.
The wrist disarticulation level raises concerns similar to those of the partial hands. Inequality of limb length and loss of sensation related to prosthetic fitting are likely to lead to rejection of a prosthesis in congenital conditions. On the other hand, traumatic injuries in older children should be treated very aggressively with prosthetic fitting within the first 30 days to facilitate the incorporation of the prosthesis into the amputee's lifestyle. Recent modifications to myoelectric components also have allowed this level of amputation to be fitted before 18 months, if desired.
The transradial level has seen the most change in design for the younger patient. Newer components have allowed the prosthetist to take a more aggressive approach with these patients. With the development of "user-friendly" myoelectric controls, the child under I½ years can learn to develop control of the prosthesis (Fig 34B-5.). This allows a more natural assimilation of the prosthesis without having to battle through the "terrible twos." Although this concept has not been proved, enough positive anecdotal evidence has been reported that it should be investigated further.
The younger child with a transhumeral condition should be fitted with either a static or friction elbow mechanism. The approach for hand function should parallel the transradial case. The older amputee should be provided with an active elbow joint. They can be expected to master either dual cable control of the elbow lock or electric control of the motorized elbow.
Midshaft or longer transhumeral conditions with normal shoulder function do not require the heavier electric elbows. These prostheses will function more quickly and quietly and with more proprioceptive feedback (via the cable and harness) with mechanical elbows. The available electric elbows should be primarily considered for patients with shorter residual limbs. At this level, the ease of control offsets the extra weight and may increase the potential for prosthetic use. As with the traumatic transradial amputees, acquired transhumeral amputees must be fitted very quickly to allow the individual to retain normal bimanual functions.
The additional requirement for prosthetic shoulder function at the shoulder disarticulation and forequarter level leads to more complications and more rejection. The prosthesis must provide a functional benefit for the amputee, or he will reject it. A compromise between weight and control simplicity must be made. All the available children's-size shoulder joints are passive, so the child must manually preposition the prosthesis' shoulder in the desired location.
Elbow and terminal device choice is based on a needs assessment of the amputee. The evaluation of the shoulder and forequarter amputee should ideally be conducted by an experienced clinic team due to the large number of prosthetic component combinations possible.
The needs of the bilateral upper-limb amputee are also best met by the experienced rehabilitation team. The child must learn to function both with and without the prostheses for the greatest independence. Because of their proprioceptive feedback, cable control of the terminal device of the prostheses should help the child's function (Fig 34B-6.). As the control and speed of electronic components improve, this trend may be reversed.
The bilateral amputee, who needs more than just prehension, will benefit from referral to a rehabilitation center that has experience with this type of condition. The challenge of these children requires familiarity with a variety of prosthetic components and the ability to combine them for the optimum function for the amputee.
SPECIAL NEEDS OF CHILD AMPUTEES
Children are not just small adults. Their life-styles and attitudes are different. They want to be independent, but they also want to fit in with their peers. They need to belong to the group and not feel like an outsider.
A child with a congenital anomaly or amputation will experience the reaction of others to their "difference."The more cosmetic the prosthesis is, the greater the chance of a positive reaction to the child. "Captain Hook" still conveys a negative image for most of our population. Therefore, cosmetic appearance does become an issue for both child and family.
The physical changes that children normally go through must be considered when designing their prostheses. The rapid growth of their limbs requires replacement of all or part of the prosthesis annually. The use of multilayered sockets or thick limb socks will delay the replacement. The use of thermoplastics that are adjustable will also help.
As noted above, the more expensive parts of electric prostheses can be reused in the next device. Several centers use the concept of "limb-banking" electric components to help reduce the cost of the prostheses. This only works if there is technical and financial support to maintain the parts.
Children can be very destructive in their normal active life-style. The prosthesis must be designed to take as much abuse as possible. They also should be provided with the adaptive equipment to have as normal a childhood as possible. The use of terminal devices designed for recreation should be encouraged (Fig 34B-7.).
Although technologies have changed, the challenges of the child amputee have not. The prosthetic fit of the growing limb must be revised annually. The more complicated cases, i.e., high-level and bilateral amputations, should be managed by clinic teams with more experience. The life-style of the child requires that the prostheses be functional, durable, and cosmetic.
New materials and equipment are allowing the fitting of lighter and more advanced prostheses. Prospective studies of these new methods of patient treatment are needed.
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Chapter 34B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles