Recent Improvements in Upper Limb Pediatrics

Not only are children fit with myoelectric arms at a much earlier age than years before, but also they are now much more functional and successful with these devices. Advancements such as microprocessor-based controls, longer lasting batteries, improved socket design, and flexible socket materials have improved the functionality of children with their prosthesis, especially children under the age of 5. These advances and can provide a greater functionality with the prosthesis compared to results of devices from just a few years ago.

Our organization has found an increasing acceptance of myoelectric control for this young population, primarily from the results received in improved socket design and components. However, the three most important criteria for functionality at this age comes from 1) a team approach, 2) continual follow up, and 3) discussions with the parents, Certified Prosthetists, PM&R Physician, Occupational Therapists, manufacturers, and other referrals such as Case Managers.

The most critical factor in any prosthesis is the socket. The socket must be comfortable, easy to don, provide adequate suspension with maximum ROM, and allow functional control of the terminal device. If there is any concern regarding function of a prosthesis, a full assessment of the socket fit must be performed. An easy guideline is an anatomical shaped flexible socket that doesn’t allow for limb movement within the socket. Any true functional assessment must take into consideration that the child is wearing an appropriate device for the specified activity. The anatomically designed socket is not only heat moldable to accommodate for growth, but also made of plastics which are flexible allowing for an increased functional ROM with terminal device control. The socket must be anatomically correct and growth adjustable.

Flexible inner socket providing growth allowance, suspension and ROM.

In recent years, the microprocessors controlling the terminal device have drastically improved, providing optimum control by the child. Not only can the gains be adjusted, but also thresholds, rate of contraction, and strategy of control. All adjustments are visually friendly on a computer or hand held PDA. Many of these devices record usage of the prosthesis, giving the rehab team and payers knowledge of the child’s incorporation of the device in their daily activities.

Adjustments to electric devices are not preformed on a computer or hand-held PDA.

Our team of specialized clinicians have found an increase in functionality with children of very young age with myoelectrics using devices such as VASI’s SPM circuit that uses a standard computer to communicate with the prosthesis, and Animated Prosthetics Inc, which uses a wireless link with a PDA to perform similar communications, or OttoBock’s coding plug setup, which uses color specified plugs to change the strategy of control.

Batteries have drastically advanced in the past few years. Unlike batteries of the past, it is recommended to attach the battery inside the prosthesis, and not clipped to the child’s clothing. This can be done because the batteries are now much smaller and lighter. Like adults, the Li-Ion cell is used more frequently giving a longer wear time and a quicker charge time. Because of this, only one battery is necessary for a couple days worth of operation, so the battery can be placed internally. This protects the battery as well as prevents misplacing the battery or the hassle of interchanging batteries. Recently, technology is progressing toward a lithium polymer cell. This is a very small, lightweight battery, drastically decreasing the weight of the prosthesis, which allows smaller and younger children the ability to wear and operate electric systems.

New Lithium Polymer battery.	Smaller electrodes don’t take up much room making the arm more cosmetic.	Thin preamplifier with gain adjustment.

The most widely used input device for children are electrodes. The standard Otto Bock style works well, but takes up considerable amount of length on the limb. Oftentimes, for children with short Radial level deficiencies under 2 years old, this electrode may not be the best option. The remote electrode preamp style works well in these situations. The electrode doesn’t take up much space on the limb, and is flat on the exterior of the socket so no bulge appears in the lamination. Also what is nice about this style is if the EMG site changes, it is very easy to move the electrode. Or, when changing to a dual site, a new socket is not necessary to just add the 2nd electrode, therefore decreasing the cost to the payer. Similar to the Otto Bock style, a gain adjustment is on the back of the preamplifier. Also remember this adjustment can be done on a computer in many systems.

Manufacturers have answered the call to make pediatric components lighter for the young child. Excluding the socket and frame, all the electronics necessary for a child under 3 years of age weigh 132 grams. Which means, the components weigh about the same as a standard cell phone. When you add the socket and frame, the entire device should weigh between ½ -1 lb; light enough that children even at 1 yr of age can handle quite well. In most cases, weight should not be a concern for myoelectrics for young children. With these new components, there is currently no study that shows a significant difference in the weight of this myoelectric that contraindicates its recommendation for young children, even as young as 1 year old.

It is of extreme importance before making conclusions about the function of a child with a prosthetic arm to evaluate the fit and ensure it has newer design principles with a flexible, anatomically correct socket. Lighter weight components, improved socket material and design, smaller electrodes, improved battery technology, and computerized adjustments have justified the successful fittings and positive results of fitting children at a very young age with an upper extremity prosthesis—even showing success with myoelectrics at one year of age. Coupled with a complete education to parents, referrals, and payors, as well as a continuous follow up care, children are maximizing their abilities with prosthetic devices.