Chapter 35B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles
Lower-Limb Deficiencies: Prosthetic and Orthotic Management
Daniel G. Oglesby, Jr., C.P.O.
Carmen Tablada, C.P.
Providing prosthetic and orthotic care for the limb-deficient child involves more than simply supplying the proper componentry. The psychological impact on the parents and family must also be considered. In most cases the very young child has no awareness of being different from his peers. It is only from the reactions of his parents and others that he learns about his disability.
The prosthetist is often able to help the family deal with these issues by discussing their concerns openly and calmly and by providing prosthetic care that encourages a normal developmental sequence for the child. Fitting and delivery of new devices must be timely to avoid adding to the child's feelings of being unable to keep up with his family and friends. Referral to a local support group can often help the family faced with the new challenge of limb deficiency. Only occasionally is referral to a professional for counseling necessary.
For the child with an acquired limb loss due to tumor or accident, there may be the added factors of fear of death or guilt over the circumstances of the amputation. The emotional scars can be even more devastating than the physical loss. The prosthetist's role is to help keep the child actively involved in normal daily activities. A well-fitted fully functional prosthesis can help keep the child and the family focused on constructive adaptation.
DEVELOPMENTAL STAGING OF COMPONENTRY
The basic principle in pediatric prosthetics is to provide components that are appropriate to the child's developmental stage. Although sophisticated mechanisms have a role in prosthetics, children's devices usually emphasize simplicity and reliability. General guidelines based on experience with many children over time can be given for when to provide a particular level of complexity. The optimum time to utilize a component for a specific child, however, must be individually determined by the clinic team.
Birth to 6 Months
Most centers do not provide lower-limb prostheses prior to 6 months of age because the child is growing so rapidly that it would be quickly outgrown. Furthermore, the child must master sitting balance and other developmental tasks before standing and walking become realistic goals. On occasion, the family may insist on prosthetic fitting, and very lightweight materials can be used. Such fittings probably have more to do with the parents' or grandparents' idea of "body image" than the child's.
7 Months to 14 Months
Most centers recommend fitting when the child is almost ready to pull to stand, which varies among individuals. The major prosthetic considerations are as follows:
- A socket that allows for rapid linear growth
- A suspension system that does not encumber the child
- Regular checkups to monitor growth and proper prosthetic length
The chief biomechanical function of the foot at this age is to fill the shoe. The child is so lightweight and the gait pattern so primitive that commercial feet are optional. Many prosthetists fashion infants' feet from lightweight and flexible polyethylene foam material that provides good balance without stress on the residual limb or next proximal joint. Knee mechanisms are unnecessary for children of this age. Most infants' prostheses are fashioned from one solid piece of balsa wood or rigid foam and covered with a lightweight plastic shell. Endoskeletal construction is also possible; one solid tube from socket to foot reduces weight by omitting the knee mechanism. When the infant with a hip disarticulation is fitted with a prosthesis, a hip joint permitting flexion is necessary to allow sitting. Once again, the knee joint is customarily omitted, and the foot is often formed of lightweight foam materials.
15 to 36 Months
During the period from 1 to 3 years of age, limb growth is the most evident change. There are several ways to accommodate the need for a longer prosthesis. At the time of initial delivery, children's prostheses are sometimes made 1.5 cm (½ in.) longer than is correct with an equivalent buildup on the opposite shoe to level the pelvis. When the parents purchase new shoes in a few months (without a lift attached), the effective length of the prosthesis is increased. It is also possible to place spacer blocks between the ankle and foot mechanism up to a point; eventually, it may be necessary to cut the prosthesis in half and add material to the shin plus relaminate. Endoskeletal designs can add longer tubes until the cosmetic cover no longer stretches any further. Although foot size will seem to lag behind as the uninvolved foot grows, this is seldom significant for the growing child. Most prosthetists advise selecting the largest possible foot size for the initial fitting in anticipation of the child's future growth.
As the musculoskeletal system matures, the family may notice variations in the toe-in or toe-out of the prosthesis. This seldom affects the child's gait significantly and can be simply observed. Only rarely will it be necessary to realign the prosthesis due to significant postural or structural changes in the maturing child. Through careful prosthetic planning and follow-up adjustments, it is common for pediatric prostheses to remain serviceable for a full year or more despite the rapid growth that is anticipated.
37 to 72 Months
During the child's preschool years, from ages 3 to 6 years, manufactured components become available in simple and basic styles. The preschooler's active lifestyle commonly results in lost or tattered clothing after a hard day at play. The prosthesis is subjected to similar rigors and must therefore be simple, rugged, and repairable.
A functional knee is commonly introduced at this age, often with a manual locking option initially. As the child masters the prosthesis, the knee can be unlocked at home and later at preschool. An extension assist aids knee stability but may need repairs from time to time. Endoskeletal designs are readily available, and the components generally fare well; the covers are another matter. Some parents gladly accept the need to replace the outside covers at intervals and eagerly embrace endoskeletal prostheses. Others prefer the ultimate durability of the exoskeletal type. Function is similar regardless of the external configuration. A few families will accept an endoskeletal device without the covering during the more destructive phases of childhood.
Commercially available feet are preferable starting at this age. Almost all pediatric designs use nonarticulated feet; the high-level or bilateral case is the possible exception. The solid-ankle, cushion-heel (SACH) design is inexpensive and reliable; dynamic-response alternatives have recently become available. Initial results suggest enthusiastic acceptance of the more responsive designs by both children and parents, although the functional differences for children are as yet undocumented.
7 to 12 Years
The elementary school child goes through minor but continual growth changes. Fit and function should be maintained by regular follow-up, at least quarterly. As the preteen years approach, both boys and girls develop interests in new "outside" activities including sports, arts, and social activities such as dancing. The youth's interests begin to have an impact on the prosthetic design as limitations of the previous artificial limb become apparent. Each new fitting offers the opportunity to vary componentry to address the increasing activities of this age group.
13 to 18 Years
During the preteen and particularly the teen years, physiologic and psychological changes are intensified- for amputee and nonamputee alike. Cosmetic appearance naturally becomes an increasing concern for both boys and girls. This is also a time of transition for the prosthetist inasmuch as he must recognize the increasing independence of the maturing amputee and develop a good working relationship that will last on into adulthood. During this period any number of considerations will arise, from abrupt changes in fashion (e.g., heel heights) to pregnancy, and each must be handled with the seriousness they deserve.
The ability to conform by being a nonconformist can become a prosthetic factor too. Some will demand that the prosthesis be inconspicuous and blend into the background, while others will insist on a garish neon color lamination as a statement of personal expression.The need to provide some means of protection from the stresses of competitive sports activities is common.
As a general rule, the prosthetic componentry and suspension will become increasingly sophisticated as the teen approaches adulthood. By the time the youth is 18 years old, adult componentry and fitting principles are fully applicable.
CONSIDERATIONS BY LEVEL OF AMPUTATION
As has been discussed, the primary factor in selection of prosthetic componentry is developmental readiness. Beyond that, durability and function become significant considerations. During the "sandbox years," simplicity and repairability may be prime requirements; as adulthood approaches, much more sophisticated prostheses are increasingly common.
Treatment for the partial-foot amputee varies according to the degree of loss. Since children are lightweight and typically have excellent vascularity, they often do very well with partial-foot amputation. When only loss of the toes is involved, a simple foam filler is usually all that is required. Unlike the case with adults, it is seldom necessary to modify the shoes themselves. This is fortunate because shoe modifications would quickly become expensive for the rapidly growing child.
Forefoot to midfoot amputations often do well with a modified University of California Biomechanics Laboratory (UCBL)-type insert that incorporates a toe filler. Once the proximal third of the foot is involved, suspension becomes a problem, and the modified ankle-foot orthosis (AFO) is one solution. Another approach is to provide a flexible laminated rubber "boot" for both function and better cosmetic appearance.
Syme Ankle Disarticulation
The Syme and similar levels play an important role in pediatric amputations since the growth plates are preserved (when compared with a transtibial level) and the risk of bony overgrowth is avoided. Furthermore, most children with Syme or Boyd amputations can ambulate short distances without any prosthesis. For the very young child there is often insufficient discrepancy to provide a commercial foot mechanism; the discrepancy usually increases as the child matures due to more rapid growth on the uninvolved side. Epiphysiodesis just prior to the cessation of growth is always an option. The SACH foot has been the only option until recently. Dynamic-response feet have been well received by adults, and some types are beginning to appear in pediatric sizes.
Transtibial (Below Knee)
Foot components are selected according to the function desired, as in adults. SACH remains most common, but dynamic-response designs, particularly for the older child, have also been well received. Many methods of suspension are suitable for this population. Cuff suspension alone may stress the ligaments if not reattached regularly as the child grows. Although a loose cuff or fork strap attached to a waist belt is more forgiving, such belts are seldom necessary and encumber the children. Many pediatric amputees do quite well with supracondylar suspension, particularly those who need a little extra mediolateral stability at the knee. Knee sleeves and the silicone suction socket (3S) design both provide suction suspension. Joints and corsets are rarely seen, being reserved primarily for the child with marked ligamentous damage to the knee.
Transfemoral (Above Knee)
The same controversies that exist regarding adult sockets apply to pediatric designs. Ischial containment and quadrilateral contours have both worked well with this age group. Many prosthetists elect to use an individualized shape for growing children that is based on the cast impression of their residual limb. The presence of significant body fat or the use of bulky diapers dictates a unique shape for the small child's socket. Knee criteria have been previously discussed; a free knee is unnecessary for the very young child.
One key factor for the hip disarticulation fitting is to plan ahead to accommodate circumferential growth of the pelvis. The knee joint is usually omitted until the child is near school age. The hip joint is provided at the outset, however, to permit sitting down. A SACH foot completes the prosthesis. Despite the simple componentry, the pediatric hip disarticulate typically does very well with a prosthesis. Presumably this is due to his small stature (short lever arms) and high energy level. Many progress to become excellent hands-free ambulators even as adults. Most centers are experimenting with thermoplastics and more flexible socket designs for all levels of amputation. Results to date look very encouraging, and further investigation is warranted.
Proximal Focal Femoral Deficiency
This limb deficiency warrants individual discussion because of the complex clinical picture it presents. Not only is there a significant limb length discrepancy, but hip joint involvement is also common. Hip abduction and flexion contractures are common. The knee is often unstable and may be difficult to palpate within the short, fleshy thigh tissues. All those factors complicate prosthetic management.
Prosthetic restoration is geared to minimize the excessive trunk bending and internal rotation of the hip that typify proximal femoral focal deficiency (PFFD) gait. This is accomplished by meticulous casting of the affected leg and pelvis while maintaining the proper rotation and hanging angle. Careful molding is necessary to achieve good ischial weight bearing rather than posterior-thigh weight bearing. In cases where the foot remains, it must be molded in a plantar-flexed position that allows good cosmesis yet permits some weight bearing on the sole of the foot. For those with telescoping hip joints, maximum elongation during casting improves ischial weight bearing during stance.
Transparent test sockets are invaluable in evaluating the above factors. Remodification of the positive model and fitting with a revised test socket is often required. Dynamic alignment is individualized but must take into account the child's age, physical findings, and any additional abnormalities. For those with concomitant upper-limb involvement, the socket brim may be utilized as a control cable anchor point.
In some cases, the clinic may elect to initially fit the young child with shoe buildups and/or an AFO. Once the child has grown somewhat, fitting with an extension prosthesis or ablation of the foot and fitting with a modified knee disarticulation prosthesis may be undertaken. Rarely, Van Nes rotation-plasty may be performed and the child is fitted with a modified transtibial prosthesis. Bilateral PFFD is a special circumstance, and surgical intervention is generally avoided. Definitive treatment with orthotic devices or with extension prostheses may be offered. As the child with bilateral PFFD grows and the extension devices become longer, endurance and balance are reduced. Many abandon external devices as they approach adulthood and choose to ambulate unencumbered.
The young person with an amputation or limb deficiency will find that his life will be different in some ways from the lives of his playmates. This does not necessarily mean that he is limited; he will be as functional as society and circumstances allow. Prosthetic restoration may enhance or detract from the amputees independence, depending upon the quality of fit and function provided. Careful attention to detail, developmentally appropriate complexity, and faithful follow-up are the cornerstones of successful pediatric prosthetics.
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Chapter 35B - Atlas of Limb Prosthetics: Surgical, Prosthetic, and Rehabilitation Principles