UPPER EXTREMITY HIGH-LEVEL AMPUTATION AND MYOELECTRIC PROSTHESIS
By Karl Fillauer, CPO, FAAOP; Fillauer, Inc.

This presentation reviews several of our personal experiences in fitting high-level transradial and humeral amputees. There are many issues that need to be considered when dealing with high-level upper limb amputees. There is more to successful fitting of an amputee than having a neat, well constructed, and fitting prosthesis. A proven protocol we follow is similar to the one we follow with other levels of amputees.

The most prevalent upper limb amputation we see is the transradial, many of which have short residual limbs. This is followed by transhumeral amputations, and again, high-level residual limbs are commonly seen, though not the majority. Shoulder and forequarter level amputations are seen infrequently but present the most challenging prosthetic fittings. The higher-level residual limbs are best suited for electric and/or myoelectric components. This is due to the fact that an amputee’s ability to operate body powered designs decreases when prosthetic functions are performed by harnessing body movements with use of cables and harnesses.

The control of an electric prosthesis is attained by an electro-mechanical switch operated by body movement using straps or cables. A myoelectric prosthesis requires EMG signals from muscles selected and the advantage is in not needing cables or straps to control the operations of the prosthesis.

Today we have a broad selection of designs and components to choose from when formulating the prosthesis for the amputee. We should remember that it is not necessary to limit your choice of design to cosmesis, body powered, electric, or myoelectric. One avenue we often take is to hybridize the components by creating a combination of designs. This often represents the most practical and best functioning prosthesis for the amputee.

We must interview the patient, discussing topics such as desired expectations and functions that they expect from the prosthesis. Knowing what the customer expects from your services is important and often neglected, resulting in unnecessary frustration. I would rather not proceed with the prosthesis knowing that I cannot meet the expectations or functional requirements by the patient. One of the common reasons we hear for not wearing the prosthesis is that it ‘gets in the way’ or it will not do what I need for it to do.

The next step is to perform an evaluation of the residual limb and joints involved. We might assume from the interview that the goals and expectations are attainable and proceed accordingly only to discover after the fact that the patient cannot operate the components satisfactorily. I recently made a body powered prosthesis for a high-level transhumeral amputee after I evaluated the residual limb and shoulder joint for strength and range of motion. During the fitting of the prosthesis I realized that this older gentleman had kyphosis resulting in very limited shoulder protraction and retraction. He was not able to create enough cable excursion to lift the forearm or open the terminal device! Shame on me, but it happens if we do not pay attention and complete a thorough evaluation. If myoelectric components are being considered, proper Myo testing is required for electrode site determination.

Often it is difficult to determine if an amputee is going to be a successful myoelectric or electric wearer by the physical examination. We have found that as part of the final phase of the evaluation, a trial fitting of a temporary or evaluation socket with the components attached answers or resolves many questions. The trial fitting should be documented for several reasons, one of which is to aid in justifying the expense to the funding source that the outcome of this procedure will enhance the functional level of the patient. Our policy is to always perform a test socket trail fitting and we believe this should be standard procedure for all myoelectric candidates.

Pre-prosthetic training is important once the determination is made that a prosthesis is to be fabricated, particularly if electric or myoelectric is to be used. The purpose or goal of pre-prosthetic training is to ensure muscle conditioning, range of motion, and muscle strength. The best prosthesis will be of little benefit if the amputee does not have the ability to control the device. Myo users also need to enhance muscle independence so that the hand or elbow can be operated effortlessly in both directions. As part of the training, we prefer to use a Myo tester such as Myolab II which is a sensitive two channel EMG monitor with audio feedback. With this device the patient is able to practice contracting their muscles, then relaxing. Having two channel readings allows the patient to both see on the monitor and hear the input generated by their muscle contraction. This helps develop independence between the two antagonistic muscles.

We feel that there are three success factors in prosthetic design that are essential: choosing the proper components, a well fitting, properly designed socket and an appropriately fitted suspension harness.

Component selection will differ between the various levels of amputation with consideration for a unilateral versus a bilateral. For the high level upper extremity amputees we usually select electric or myoelectric terminal devices and elbow. Body powered components are not ruled out and may be used in conjunction with other systems.

Component selection will differ between the various levels of amputation with consideration for a unilateral versus a bilateral. For the high level upper extremity amputees we usually select electric or myoelectric terminal devices and elbow. Body powered components are not ruled out and may be used in conjunction with other systems.

Harnessing both for suspension and for function is often treated as less than important. We have seen the prostheses discarded way too often due to poor harnessing technique and/or fit. Upper extremity manuals illustrate various harness configurations that are helpful if used as a starting point. Harnessing is very specific to the individual and what works for one amputee may not be adequate for another. The prosthetist must be creative in harness design, trying several systems in many of the cases.

Harnessing both for suspension and for function is often treated as less than important. We have seen the prostheses discarded way too often due to poor harnessing technique and/or fit. Upper extremity manuals illustrate various harness configurations that are helpful if used as a starting point. Harnessing is very specific to the individual and what works for one amputee may not be adequate for another. The prosthetist must be creative in harness design, trying several systems in many of the cases.

There are many prosthetic considerations that can be discussed in great detail. While reviewing the forthcoming case studies, we will highlight many considerations that helped determine the final prosthesis. The various groups or categories we will overview will be acquired and congenital absence of the upper limb. The prosthetic design and considerations often differ between these two general groups. Congenital amputees may have partially developed or missing bones that are often fused. The soft tissue is commonly heavy or thick and ideal for weight loading. The acquired group will often exhibit scarring, graphed skin areas, muscle atrophy and limited range of motion.

Fillauer LLC
Hosmer Dorrance Corporation
Motion Control
Center for Orthotics Design
Centri