An Upper-Limb Prosthesis for Infants
H. G. WATTS, MD*, J. CORIDEO, CP**,AND M. DOW, LOT***Philadelphia, Pennsylvania
Current wisdom dictates that an infant born with an upper-limb deficiency should be fitted with a prosthesis at about the time the child begins sitting. Some have advocated even earlier fitting-when the child begins to bring the hands together.
When selecting a prosthesis for initial fitting, three problems need to be considered: the weight of the appliance, the rapid growth of the infant and the choice of an appropriate terminal device. Fabricating the prosthesis from polypropylene solves the problem of weight. It is also possible to heat polypropylene to alter its shape, thereby readily accommodating change in prosthesis size necessitated by growth. Fabricating the prosthetic shell from polypropylene is relatively inexpensive.
The array of terminal devices for infants is rather limited. Functional devices, that is, those with moving parts designed to provide passive or active prehension, are relatively heavy. A simple mitt or a polypropylene paddle allows a child to bat at a ball or a noisy toy but does not allow any grasp. Absence of prehension may be solved in part by cementing a patch of Velcro loop material to the palmar surface of the mitt and providing toys to which Velcro hook material has been attached. This technique is not ideal because the fixed pronation/supination position of the paddle hinders toy placement with the contralateral hand by the child.
Another approach to the problem of infant bimanual function is a spherical terminal device covered with Velcro loop material. This allows an object to which the hook material of Velcro has been cemented to be affixed to the device in any position. We have found that the Velcro-covered sphere allows "semifunctional" bimanual activities for infants.
Fabrication of the prosthesis is accomplished by standard techniques. Polypropylene, 1/8-in. thick, is vacuum-formed over a positive plaster mold made from a negative mold of the amputation limb. A socket with supracondylar suspension is usually satisfactory. A 1-cm (1/2-in.) hole is cut in the midforearm section to allow the use of a stockinette to pull the amputation limb into the socket. For above-elbow deficiencies, standard suspension can be used, with the socket bent to a "banana shape." The terminal device is made from a solid ball of polypropylene 4 cm (1 1/2 in.) in diameter which is heat-welded to the socket. The sphere is covered with Velcro loop material which is cemented in place. The completed prosthesis weighs approximately 150 gr (5.3 oz.).
Soft, light-weight toys can be adapted with Velcro hook material, either cemented or sewn in place.
Some parents of infants fitted with the polypropylene prostheses have noted that crawling is more difficult, in part because the smooth plastic forearm slips on the floor. One parent glued a patch of moleskin on the extensor surface of the forearm to reduce the problem. Such a "crawling patch" may be a useful addition for all infant upper-limb prostheses.
The polypropylene prosthesis with spherical terminal device has been fitted to three infants. The child in Figure 1 was 14 months old when fitted but was significantly delayed developmentally. The new infant prosthesis should be in widespread use, for it is likely to prove to be a useful addition to the armamentarium of clinics treating infants.
*King Faisal Specialist Hospital, Box 3354, Riyadh, Saudi Arabia
**Mobility Systems, 5 Peabody Road, Derry, NH 03038
***Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19152