Microprocessor-Controlled Prostheses for the Lower Limb
Microprocessor-controlled prostheses use feedback from sensors to adjust joint movement on a real-time as- needed basis. Active joint control is intended to improve safety and function, particularly for individuals who have the capability to maneuver on uneven terrain and with a variable gait.
More than one hundred different prosthetic knee designs are currently available (e.g. Intelligent Prosthesis, Adaptive, Rheo Knee®, C-Leg®, Genium™ Bionic Prosthetic System, Seattle Power Knees; 3 models include Single Axis, 4-bar, and Fusion). The choice of the most appropriate design depends on the individual’s activity level. Key elements of a prosthetic knee design involve providing stability during both the stance and swing phase of the gait. Prosthetic knees also vary in their ability to alter the cadence of the gait, or the ability to walk on rough or uneven surfaces. In contrast to more simple prostheses, which are designed to function optimally at one walking cadence, fluid and hydraulic-controlled devices are designed to allow amputees to vary their walking speed by matching the movement of the shin portion of the prosthesis to the movement of the upper leg. Hydraulic prostheses are heavier than other options and require gait training; for these reasons, these prostheses are generally prescribed for athletic or fit individuals.
Microprocessor-controlled ankle-foot prostheses are being developed for transtibial amputees, (e.g. Proprio Foot®, iPED, Endolite élan, Kinnex, Raize, Triton Smart Ankle, emPOWER). With sensors in the feet that determine the direction and speed of the foot’s movement, a microprocessor controls the flexion angle of the ankle, allowing the foot to lift during the swing phase and potentially adjust to changes in force, speed, and terrain during the step phase. The intent of the technology is to make ambulation more efficient and prevent falls.
Currently in the launch phase in the U.S. are lower-limb powered prostheses that are designed to replace the muscle activity of the quadriceps. It uses artificial proprioception with sensors in order to bend and straighten the prosthetic joint and respond to the appropriate movement required for the next step, (e.g. Power Knee [Ossur], PowerFoot BiOM ®).
A microprocessor-controlled knee is considered medically necessary if the medical appropriateness criteria are met. (See Medical Appropriateness below.)
A powered knee is considered investigational.
A microprocessor-controlled or powered foot is considered investigational.
A microprocessor-controlled knee in an amputee is considered medically appropriate if ALL of the following are met:
Physical ability, including adequate cardiovascular and pulmonary reserve, for ambulation at faster than normal walking speed
Demonstrated need for long distance ambulation at variable rates or for ambulation on uneven terrain (use of the limb in the home or for basic community ambulation, including negotiation of stairs, is not sufficient to justify provision of the computerized limb over standard limb applications)
Adequate cognitive ability to master use and care requirements for the technology
Any specific products referenced in this policy are just examples and are intended for illustrative purposes only. It is not intended to be a recommendation of one product over another, and is not intended to represent a complete listing of all products available. These examples are contained in the parenthetical e.g. statement.
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.
Microprocessor-controlled prostheses are categorized as Class I, exempt devices. Manufacturers must register prostheses with the restorative devices branch of FDA and keep a record of any complaints but do not have to undergo a full FDA review.
Medicare uses the following functional ability levels when determining medical necessity:
Level 0. Does not have the ability or potential to ambulate or transfer safely with or without assistance and a prosthesis does not enhance their quality of life or mobility.
Level 1. Has the ability or potential to use a prosthesis for transfers or ambulation on level surfaces at fixed cadence. Typical of the limited and unlimited household ambulatory.
Level 2. Has the ability or potential for ambulation with the ability to traverse low level environmental barriers such as curbs, stairs, or uneven surfaces. Typical of the limited community ambulatory.
Level 3. Has the ability or potential for ambulation with variable cadence. Typical of the community ambulator who has the ability to traverse most environmental barriers and may have vocational, therapeutic, or exercise activity that demands prosthetic utilization beyond simple locomotion.
Level 4. Has the ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels. Typical of the prosthetic demand of the child, active adult, or athlete.
The limited evidence available to date does not support an improvement in functional outcomes with a microprocessor-controlled or powered ankle-foot prostheses compared with standard prostheses.
Alimusaj, M., Laetitia,F., Braatz, F., Gerner, H., and Wolf, S. (2009). Kinematics and kinetics with an adaptive ankle foot system during stair ambulation of transtibial amputees. Gait & Posture, 30, 356-363. (Level 4 evidence)
BlueCross BlueShield Association. Evidence Positioning System. (4:2018). Microprocessor-controlled prostheses for the lower limb (1.04.05). Retrieved November 16, 2018 from http://www.evidencepositioningsystem.com. (26 articles and/or guidelines reviewed)
Cherelle, P., Grosu, V., Cestari, M., Vanderborght, B., and Lefeber, D. (2016) The AMP‑Foot 3, new generationpropulsive prosthetic feet with explosive motion characteristics: design and validation.BioMedical Engineering, 15(3), 145-163. (Level 4 evidence)
CMS.gov: Center for Medicare & Medicaid Services, CGS Administrators, LLC. (2018, November) Lower limb prostheses (LCD ID: L33787). Retrieved November 16, 2018 from http://www.cms.gov.
Delussu, A., Brunelli, S., Paradisi, F., Iosa, M., Pellegrini, R., Zenardi, D., et al. (2013, March). Assessment of the effects of carbon fiber and bionic foot during overground and treadmill walking in transtibial amputees. Gait & Posture, e-published ahead of print http://dx.doi.org/10.1016/j.gaitpost.2013.04.009. (Level 5 evidence)
Fradet, L., Alimusaj, M., Braatz, F., and Wolf, S. (2010, April). Biomechanical analysis of ramp ambulation of transtibial amputees with an adaptive ankle foot system. Gait & Posture, e-published ahead of print doi:10.1016/j. gaitpost.2010.04.011. (Level 5 evidence)
Gailey, R., Gaunaurd, I., Agrawal, V., Finnieston, A., O’Toole, C., and Tolchin, R. (2012). Application of self-report and performance-based outcome measures todetermine functional differences between four categories of prosthetic feet. Journal of Rehabilitation, Research and Development (JRRD), 49(4), 597-612. (Level 4 evidence)
Kannenberg, A., Zacharias, D., & Pröbsting, E. (2014). Benefits of microprocessor-controlled prosthetic knees to limited community ambulators: systematic review. Journal of Rehabilitation Research & Development, 51, (10), 1469-1496. (Level 1 evidence)
Rosenblatt, N., Bauer, A., Rotter, D., and Grabiner, M. (2014). Active dorsiflexing prostheses may reduce trip-related fall risk in people with transtibial amputation. Journal of Rehabilitation Research & Development (JRRD), 51 (8), 1229-1242. (Level 4 evidence)
Struchkov, V. and Buckley, J. (2015, November). Biomechanics of ramp descent in unilateral trans-tibial amputees: Comparison of a microprocessor controlled foot with conventional ankle–foot mechanisms. Clinical Biomechanics, 32 (2016), 164-170. (Level 4 evidence)
Theeven, P., Hemmen, B., Brink, P., Smeets, R., & Seelen, H. (2013). Measures and procedures utilized to determine the added value of microprocessor-controlled prosthetic knee joints: a systematic review. BMC Musculoskeletal Disorders, 14:333. (Level 1 evidence)
U.S. Food and Drug Administration. (1999, July). Center for Devices and Radiological health. 510(k) Premarket Notification Database. K991590. Retrieved January 24, 2017 from http://www.accessdata.fda.gov.
Wolf, S., Alimusaj, M., Fradet, L., Siegel, J., and Braatz, F. (2009) Pressure characteristics at the stump/socket interface in transtibial amputees using an adaptive prosthetic foot. Clinical Biomechanics, e-published http://dx.doi.org/10.1016/j.clinbiomech.2009.08.007. (Level 4 evidence)
ORIGINAL EFFECTIVE DATE: 11/13/2010
MOST RECENT REVIEW DATE: 2/14/2019
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