Myoelectric Prosthetic Components for the Upper Limb
DESCRIPTION
Myoelectric prostheses are powered by electric motors with an external power source. The joint movement of an upper limb prosthesis (e.g., hand, wrist, and/or elbow) is driven by microchip-processed electrical activity in the muscles of the remaining limb stump.
Upper limb prostheses are used for amputations at any level from the hand to the shoulder. The need for a prosthesis can occur for a number of reasons, including trauma, surgery, or congenital anomalies. The primary goals of the upper limb prosthesis are to restore natural appearance and function. Achieving these goals also requires sufficient comfort and ease of use for continued acceptance by the wearer. The difficulty of achieving these diverse goals with an upper limb prosthesis increases as the level of amputation (digits, hand, wrist, elbow, and shoulder), and thus the complexity of joint movement, increases.
Upper limb prostheses are classified into three categories depending on the means of generating movement at the joints: passive, body-powered, and electrically powered movement. All three types of prostheses have been in use for over 30 years; each possesses unique advantages and disadvantages.
The passive prosthesis is the lightest of the three types and is described as the most comfortable. Since the passive prosthesis must be repositioned manually, typically by moving it with the opposite arm, it cannot restore function.
The body-powered prosthesis uses a body harness and cable system to provide functional manipulation of the elbow and hand. Voluntary movement of the shoulder and/or limb stump extends the cable and transmits the force to the terminal device. Prosthetic hand attachments, which may be claw-like devices that allow good grip strength and visual control of objects or latex-gloved devices that provide a more natural appearance at the expense of control, can be opened and closed by the cable system. Patient complaints with body-powered prostheses include harness discomfort, particularly the wear temperature, wire failure, and the unattractive appearance.
Myoelectric prostheses use muscle activity from the remaining limb for the control of joint movement. Electromyographic (EMG) signals from the limb stump are detected by surface electrodes, amplified, and then processed by a controller to drive battery-powered motors that move the hand, wrist, or elbow. Although upper arm movement may be slow and limited to one joint at a time, myoelectric control of movement may be considered the most physiologically natural. Myoelectric hand attachments are similar in form to those offered with the body-powered prosthesis, but are battery powered. An example of recently available technology is the SensorHand™ by Advanced Arm Dynamics, which is described as having an AutoGrasp feature, an opening/closing speed of up to 300 mm/second, and advanced EMG signal processing. Patient dissatisfaction with myoelectric prostheses includes the increased cost, maintenance (particularly for the glove), and weight.
A hybrid system, a combination of body-powered and myoelectric components, may be used for high-level amputations (at or above the elbow). Hybrid systems allow control of two joints at once (i.e., one body-powered and one myoelectric) and are generally lighter and less expensive than a prosthesis composed entirely of myoelectric components.
Technology in this area is rapidly changing, driven by advances in biomedical engineering and by the U.S. Department of Defense Advanced Research Projects Agency (DARPA), which is funding a public and private collaborative effort on prosthetic research and development. Areas of development include the use of skin-like silicone elastomer gloves, “artificial muscles,” and sensory feedback. Smaller motors, microcontrollers, implantable myoelectric sensors, and re-innervation of remaining muscle fibers are being developed to allow fine movement control. Lighter batteries and newer materials are being incorporated into myoelectric prostheses to improve comfort.
Examples of myoelectric devices include the Otto Bock myoelectric prosthesis (Otto Bock), the LTI Boston Digital Arm™ System (Liberating Technologies Inc.), and the Utah Arm Systems (Motion Control). Manufacturers must register prostheses with the restorative devices branch of the U.S. Food and Drug Administration (FDA) and keep a record of any complaints, but do not have to undergo a full FDA review.
POLICY
Myoelectric upper limb prosthetic components to restore upper limb function are considered medically necessary if the medical appropriateness criteria are met. (See Medical Appropriateness below.)
Myoelectric upper limb prosthetic components in individuals who do not meet the medical appropriateness criteria are considered not medically necessary.
MEDICAL APPROPRIATENESS
Myoelectric upper limb prosthetic components for an individual are considered medically appropriate when ALL the following criteria are met:
Has an amputation or missing limb at the wrist or above (forearm, elbow, etc.)
Standard body-powered prosthetic devices cannot be used or are insufficient to meet the functional needs for performing activities of daily living
Remaining musculature of the arm(s) contains the minimum microvolt threshold to allow operation of a myoelectric prosthetic device as evidenced by an EMG study
Has demonstrated sufficient neurological and cognitive function to operate the prosthesis effectively
Is free of comorbidities that could interfere with function of the prosthesis (neuromuscular disease, etc.)
Functional evaluation indicates that with training, use of a myoelectric prosthesis is likely to meet the functional needs of the individual (e.g., gripping, releasing, holding, and coordinating movement of the prosthesis) when performing activities of daily living. This evaluation should consider the individual’s needs for control, durability (maintenance), function (speed, work capability), and usability
Has successfully completed a trial period of one month to evaluate the tolerability and efficacy of the prosthesis in a real life setting
IMPORTANT REMINDER
We develop Medical Policies to provide guidance to Members and Providers. This Medical Policy relates only to the services or supplies described in it. The existence of a Medical Policy is not an authorization, certification, explanation of benefits or a contract for the service (or supply) that is referenced in the Medical Policy. For a determination of the benefits that a Member is entitled to receive under his or her health plan, the Member’s health plan must be reviewed. If there is a conflict between the Medical Policy and a health plan, the express terms of the health plan will govern.
ADDITIONAL INFORMATION
Amputees should be evaluated by an independent qualified professional to determine the most appropriate prosthetic components and control mechanism. Typically, this assessment is by a certified orthotist and/or prosthetist who is a healthcare professional specifically educated and trained to manage comprehensive orthotic and/or prosthetic patient care. This includes patient assessment, formulation of a treatment plan, implementation of the treatment plan, follow-up and practice management.
For individuals in whom the potential benefits of myoelectric prosthetic components for the upper limb are uncertain, individuals may first be fitted with a standard prosthesis to determine their level of function with the standard device.
SOURCES
BlueCross BlueShield Association. Medical Policy Reference Manual. (3:2010). Myoelectric prosthesis for the upper limb (1.04.04). Retrieved May 17, 2010 from BlueWeb. (9 articles and/or guidelines reviewed)
Egermann, M., Kasten, P., & Thomsen, M. (2009). Myoelectric hand prostheses in very young children. International Orthopaedics, 33 (4), 1101-1105.
Lindner, H., Linacre, J., & Norling, Hermansson L. (2009). Assessment of capacity for myoelectric control: Evaluation of construct and rating scale. Journal of Rehabilitation Medicine, 41(6), 467-474.
ORIGINAL EFFECTIVE DATE: 11/13/2010
MOST RECENT REVIEW DATE: 11/13/2010
ID_BA
Policies included in the Medical Policy Manual are not intended to certify coverage availability. They are medical determinations about a particular technology, service, drug, etc. While a policy or technology may be medically necessary, it could be excluded in a member's benefit plan. Please check with the appropriate claims department to determine if the service in question is a covered service under a particular benefit plan. Use of the Medical Policy Manual is not intended to replace independent medical judgment for treatment of individuals. The content on this Web site is not intended to be a substitute for professional medical advice in any way. Always seek the advice of your physician or other qualified health care provider if you have questions regarding a medical condition or treatment.
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