Lower Limb Prostheses

For any item to be covered by Medicare, it must: 1) be eligible for a defined Medicare benefit category, 2) be reasonable and necessary for the diagnosis or treatment of illness or injury or to improve the functioning of a malformed body member, and 3) meet all other applicable Medicare statutory and regulatory requirements.

The purpose of a Local Coverage Determination (LCD) is to provide information regarding “reasonable and necessary” criteria based on Social Security Act § 1862(a)(1)(A) provisions.

In addition to the “reasonable and necessary” criteria contained in this LCD there are other payment rules, which are discussed in the following documents, that must also be met prior to Medicare reimbursement:

• The LCD-related Standard Documentation Requirements Article, located at the bottom of this policy under the Related Local Coverage Documents section.

• The LCD-related Policy Article, located at the bottom of this policy under the Related Local Coverage Documents section.

• Refer to the Supplier Manual for additional information on documentation requirements.

• Refer to the DME MAC web sites for additional bulletin articles and other publications related to this LCD.

For the items addressed in this LCD, the “reasonable and necessary” criteria, based on Social Security Act § 1862(a)(1)(A) provisions, are defined by the following coverage indications, limitations and/or medical necessity.

A lower limb prosthesis is covered when the beneficiary:

1. Will reach or maintain a defined functional state within a reasonable period of time; and

2. Is motivated to ambulate.

FUNCTIONAL LEVELS:

A determination of the medical necessity for certain components/additions to the prosthesis is based on the beneficiary’s potential functional abilities. Potential functional ability is based on the reasonable expectations of the treating practitioner and prosthetist, considering factors including, but not limited to:

1. The beneficiary’s past history (including prior prosthetic use if applicable); and

2. The beneficiary’s current condition including the status of the residual limb and the nature of other medical problems; and

3. The beneficiary’s desire to ambulate.

Clinical assessments of beneficiary rehabilitation potential must be based on the following classification levels (see the FUNCTIONAL LEVEL CHARACTERISTICS section in the LCD related Policy Article for additional details):

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 ambulator.

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 ambulator.

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 demands of the child, active adult, or athlete.

The medical records must document the beneficiary’s current functional and physical capabilities and their expected functional potential, including an explanation for the difference, if that is the case. It is recognized, within the functional classification hierarchy, that bilateral amputees often cannot be strictly bound by functional level classifications.

GENERAL:

If a prosthesis is denied as not reasonable and necessary, related additions will also be denied as not reasonable and necessary.

When an initial below knee prosthesis (L5500) or a preparatory below knee prosthesis (L5510, L5520,L5530, L5540) is provided, prosthetic substitutions and/or additions of procedures and components are covered in accordance with the functional level assessment except for codes L5629, L5638, L5639, L5646, L5647, L5704, L5785, L5962, and L5980 which will be denied as not reasonable and necessary. When a below knee preparatory prefabricated prosthesis (L5535) is provided, prosthetic substitutions and/or additions of procedures are covered in accordance with the functional level assessment except for codes L5620, L5629, L5645, L5646, L5670, L5676, L5704, and L5962 which will be denied as not reasonable and necessary.

When an above knee initial prosthesis (L5505) or an above knee preparatory (L5560, L5570, L5580, L5590, L5595, L5600) prosthesis is provided, prosthetic substitution and/or additions of procedures and components are covered in accordance with the functional level assessment except for codes L5610, L5631, L5640, L5642, L5644, L5648, L5705, L5706, L5964, L5980, and L5710, L5711, L5712, L5714, L5716, L5718, L5722, L5724, L5726, L5728, L5780, L5790, L5795 which will be denied as not reasonable and necessary. When an above knee preparatory prefabricated prosthesis (L5585) is provided, prosthetic substitution and/or additions of procedures and components are covered in accordance with the functional level assessment except for codes L5624, L5631, L5648, L5651, L5652, L5705, L5706, L5964, and L5966 which will be denied as not reasonable and necessary.

In the following sections, the determination of coverage for selected prostheses and components with respect to potential functional levels represents the usual case. Exceptions will be considered in an individual case if additional documentation is included which justifies the medical necessity. Prostheses will be denied as not reasonable and necessary if the beneficiary’s potential functional level is 0.

FEET:

A determination of the type of foot for the prosthesis will be made by the treating practitioner and/or the prosthetist based upon the functional needs of the beneficiary. Basic lower extremity prostheses include a SACH foot. Other prosthetic feet are considered for coverage based upon functional classification.

An external keel SACH foot (L5970) or single axis ankle/foot (L5974) is covered for beneficiaries whose functional level is 1 or above.

A flexible-keel foot (L5972) or multiaxial ankle/foot (L5978) is covered for beneficiaries whose functional level is 2 or above.

A microprocessor-controlled ankle foot system (L5973), energy storing foot (L5976), dynamic response foot with multi-axial ankle (L5979), flex foot system (L5980), flex-walk system or equal (L5981), or shank foot system with vertical loading pylon (L5987) is covered when one of the following criteria is met:

1. The beneficiary’s functional level is 3 or above; or,

2. The beneficiary's functional level is 2; and,

   1. Meets the functional level 2 coverage criteria for a fluid, pneumatic, or electronic/microprocessor control addition for a prosthetic knee; and,

   2. A higher-level (i.e., functional level 3) foot is required for the safe and proper use of the prescribed knee system.

The microprocessor foot or ankle system addition with power assist which includes any type motor (L5969) is not covered because there is insufficient information to demonstrate that the item meets the Medicare standard to be considered reasonable and necessary as per PIM Chapter 13. Claims for L5969 will be denied as not reasonable and necessary.

Coverage is extended only if there is sufficient clinical documentation of functional need for the technologic or design feature of a given type of foot. This information must be retained in the treating practitioner's or prosthetist's files.

A user-adjustable heel height feature (L5990) will be denied as not reasonable and necessary.

KNEES:

A determination of the type of knee for the prosthesis will be made by the treating practitioner and/or the prosthetist based upon the functional needs of the beneficiary. Basic lower extremity prostheses include a single axis, constant friction knee. Other prosthetic knees are considered for coverage based upon functional classification.

A high activity knee control frame (L5930) is covered for beneficiaries whose functional level is 4.

A fluid or pneumatic knee unit (L5610, L5613, L5614, L5615, L5722, L5724, L5726, L5728, L5780, L5814, L5822, L5824, L5826, L5828, L5830, L5840, and L5841), or control addition, fluid (L5848), or electronic/microprocessor (L5856, L5857, L5858) is covered for beneficiaries whose functional level is 3 or above.

A fluid or pneumatic knee unit (L5610, L5613, L5614, L5615, L5722, L5724, L5726, L5728, L5780, L5814, L5822, L5824, L5826, L5828, L5830, L5840, and L5841), or control addition, fluid (L5848), or electronic/microprocessor (L5856, L5857, L5858) is also covered under limited circumstances for beneficiaries whose functional level is 2, when all of the following criteria (1-3) are met (see the POLICY SPECIFIC DOCUMENTATION REQUIREMENTS section in the LCD related Policy Article):

1. The beneficiary has had a clinical evaluation to determine their functional level (see FUNCTIONAL LEVELS section above); and,

2. Supporting documentation in the medical record outlines, in the context of the beneficiary’s overall medical health, the rationale for selection of a fluid, pneumatic, or electronic/microprocessor-controlled knee, including (at minimum) how the selected knee will:

   1. Improve the beneficiary’s functional health outcomes (e.g., fall reduction, injury prevention, lower energy expenditure); and,

   2. Help the beneficiary accomplish their activities of daily living (ADLs); and,

3. Lower-level knee systems (e.g., knee systems which exclude use of fluid, pneumatic, or microprocessor) have been considered and ruled out based on the beneficiary’s specific functional and medical needs.

In addition, for coverage of an electronic/microprocessor-controlled knee system (L5856, L5857, or L5858 plus associated components) for beneficiaries whose functional level is 2, all of the following criteria (1-4) must also be met (see the POLICY SPECIFIC DOCUMENTATION REQUIREMENTS section in the LCD related Policy Article):

1. The electronic/microprocessor knee is indicated for functional level 2; and,

2. The electronic/microprocessor knee has integrated technology that allows the knee to detect when the user trips or stumbles and can automatically adjust to stabilize the knee unit (e.g., stumble recovery); and,

3. The beneficiary is able to make use of a product that requires daily charging; and,

4. The beneficiary is able to understand and respond to error alerts and alarms indicating problems with the function of the unit.

L5859 (ADDITION TO LOWER EXTREMITY PROSTHESIS, ENDOSKELETAL KNEE-SHIN SYSTEM, POWERED AND PROGRAMMABLE FLEXION/EXTENSION ASSIST CONTROL, INCLUDES ANY TYPE MOTOR(S)) is only covered when the beneficiary meets all of the criteria below:

1. Has a microprocessor (swing and stance phase type (L5856)) controlled (electronic) knee

2. K3 functional level only

3. Has a documented comorbidity of the spine and/or sound limb affecting hip extension and/or quadriceps function that impairs K3 level function with the use of a microprocessor-controlled knee alone

4. Is able to make use of a product that requires daily charging

5. Is able to understand and respond to error alerts and alarms indicating problems with the function of the unit

If these coverage criteria for the knee component are not met, L5859 will be denied as not reasonable and necessary.

Other knee systems (L5611, L5616, L5710, L5711, L5712, L5714, L5716, L5718, L5810, L5811, L5812, L5816, L5818) are covered for beneficiaries whose functional level is 1 or above.

Coverage is extended only if there is sufficient clinical documentation of functional need for the technologic or design feature of a given type of knee. This information must be retained in the treating practitioner's or prosthetist's files.

ANKLES:

An axial rotation unit (L5982, L5984, L5985, L5986) is covered for beneficiaries whose functional level is 2 or above.

HIPS:

A pneumatic or hydraulic polycentric hip joint (L5961) is covered for beneficiaries whose functional level is 3 or above.

SOCKETS:

More than 2 test (diagnostic) sockets (L5618, L5620, L5622, L5624, L5626, L5628) for an individual prosthesis are not reasonable and necessary unless there is documentation in the medical record which justifies the need. Exception: A test socket is not reasonable and necessary for an immediate prosthesis (L5400, L5410, L5420, L5430, L5450, L5460).

No more than two of the same socket inserts (L5654, L5655, L5656, L5658, L5661, L5665, L5673, L5679, L5681, L5683) are allowed per individual prosthesis at the same time.

Socket replacements are considered reasonable and necessary if there is adequate documentation of functional and/or physiological need. It is recognized that there are situations where the explanation includes but is not limited to: changes in the residual limb; functional need changes; or irreparable damage or wear/tear due to excessive beneficiary weight or prosthetic demands of very active amputees.

GENERAL

A Standard Written Order (SWO) must be communicated to the supplier before a claim is submitted. If the supplier bills for an item addressed in this policy without first receiving a completed SWO, the claim shall be denied as not reasonable and necessary.

For Durable Medical Equipment, Prosthetics, Orthotics and Supplies (DMEPOS) base items that require a Written Order Prior to Delivery (WOPD), the supplier must have received a signed SWO before the DMEPOS item is delivered to a beneficiary. If a supplier delivers a DMEPOS item without first receiving a WOPD, the claim shall be denied as not reasonable and necessary. Refer to the LCD-related Policy Article, located at the bottom of this policy under the Related Local Coverage Documents section.

For DMEPOS base items that require a WOPD, and also require separately billed associated options, accessories, and/or supplies, the supplier must have received a WOPD which lists the base item and which may list all the associated options, accessories, and/or supplies that are separately billed prior to the delivery of the items. In this scenario, if the supplier separately bills for associated options, accessories, and/or supplies without first receiving a completed and signed WOPD of the base item prior to delivery, the claim(s) shall be denied as not reasonable and necessary.

An item/service is correctly coded when it meets all the coding guidelines listed in CMS HCPCS guidelines, LCDs, LCD-related Policy Articles, or DME MAC articles. Claims that do not meet coding guidelines shall be denied as not reasonable and necessary/incorrectly coded.

Proof of delivery (POD) is a Supplier Standard and DMEPOS suppliers are required to maintain POD documentation in their files. Proof of delivery documentation must be made available to the Medicare contractor upon request. All services that do not have appropriate proof of delivery from the supplier shall be denied as not reasonable and necessary.

Background

Lower extremity amputation is the loss or surgical removal of part of the lower limb as a result of disease, trauma, malignant tumors, or congenital anomaly. Approximately 180,000 lower extremity amputations are performed in the United States annually.¹ Diabetes and peripheral vascular disease are the leading causes of lower extremity amputation in the United States,² accounting for more than half of the nearly 100,000 major (i.e., proximal to the ankle) lower limb amputations per year.³

Loss of a lower limb negatively affects functional performance, at home and in the community, due to the importance of the lower extremity for balance, transferring, and ambulation. Lower limb amputation is associated with reduced mobility and an increased risk of falling.^4,5 A prosthetic knee is a component of the prosthesis required by an individual with a transfemoral, knee disarticulation, or hip disarticulation amputation to help restore functional ability. With over 220 prosthetic knee products available, appropriate selection, based on an amputee's medical condition and rehabilitation goals, is of critical importance for a successful outcome.^6,7 An individual with a lower limb amputation can be classified based on their ability or potential to function with a prosthesis, which may assist in the selection of a suitable prosthetic knee joint.⁸

Prosthetic knees can be categorized based on their mechanism of control, either mechanical or microprocessor. A mechanical knee joint, or non-microprocessor-controlled knee (NMPK), can achieve control by manual locking, friction, or hydraulic or pneumatic valves that are adjusted during the prosthetic fitting. A microprocessor controlled prosthetic knee (MPK) uses integrated sensors and a microcomputer that collect and analyze data (e.g., movement, timing, position, velocity), and then adjusts, in real time, the flexion and extension resistance of the prosthetic joint during the swing- and/or stance-phase of the gait cycle.⁹ Multiple MPK products are available with variable integration of microprocessor technology.¹⁰ Microprocessor controlled knees can be activated only in swing phase, stance phase, or can provide both swing- and stance-phase control. The proposed benefits of MPKs compared with NMPKs include improved overall stability when standing and walking (e.g., navigation of ramps, stairs, and uneven terrain).^9,11 The addition of integrated technology to MPKs allows the knee to detect when the user trips or stumbles, then automatically increases resistance in the knee to provide support for recovery and potentially prevent a fall.

Microprocessor controlled prosthetic knees are currently covered by Medicare for beneficiaries classified as Medicare Functional Classification Level (MFCL) 3 or above, who have, at minimum, the ability or potential for ambulation with variable cadence. This summary of evidence will focus on the use of MPKs in limited community ambulators, classified as MFCL-2, who are described as having the ability or potential for ambulation with the ability to traverse low level environmental barriers such as curbs, stairs, or uneven surfaces. Specifically, the analysis will concentrate on rate of falls, risk of falling, fear of falling, and gait performance with MPKs with integrated technology that allows the knee to detect when the user trips or stumbles and can automatically adjust to stabilize the knee unit compared to NMPKs in MFCL-2 Medicare beneficiaries with lower limb amputations requiring a prosthetic knee.

Measures of Fall Rate, Risk of Falling, Fear of Falling, and Rehabilitation Potential in Individuals with Lower Limb Loss

In the community setting, more than 50% of individuals with lower limb amputation fall anually,^12-14 compared to the reported 26% fall rate in individuals without lower limb amputation over a 2-year period.¹⁵ Nearly 50% of individuals with lower limb amputation report a fear of falling.¹⁴ The consequences of falls in lower limb prosthetic users may include activity limitation, increased injuries, increased fear of falling, and reduced quality of life.^16-18 Factors that have been associated with fall rate and fall risk in individuals with lower limb amputations include the presence of other comorbidities (i.e., vascular disease), balance confidence,¹⁴ balance ability,¹⁹ time since amputation, and age.¹²

The challenges of determining fall rate and identifying individuals using a lower limb prosthetic who are at risk of falling have been described in the literature.²⁰ First, the definition of falls in lower limb prosthetic users is not uniform and lacks prosthetic-specific language (e.g., was the individual wearing their prosthetic at the time of the fall).^5,21 Second, the majority of fall research is retrospective in design and based on self-reported outcome measures (e.g., fall history) which may introduce recall and response bias into the studies.^5,16 And, finally, many performance-based tests of balance and mobility that have been used to screen for the risk of falling in patients with lower limb amputation are not specific to this population,²⁰ are not routinely administered in clinical practice,^22,23 and are rarely prospectively validated.^18,24

In addition to patient-reported fall rates, other self-reported outcome measures that have been used in studies to examine balance and mobility in individuals with lower limb amputations include, but are not limited to: (1) the Prosthesis Evaluation Questionnaire Addendum (PEQ-A) – a questionnaire to quantify balance confidence, stumbles and falls, and concentration;²⁵ (2) the Activities-specific Balance Confidence Scale (ABC) – a survey to assess how confident a patient is that they will not lose balance in 16 different tasks;²⁰ and, (3) the Prosthetic Limb Users Survey of Mobility (PLUS-M) – a survey which evaluates perceived ability to complete household and outdoor ambulation activities.^20,26

Performance-based outcome measures that have been used in studies to examine the risk of falls in individuals with lower limb amputations include, but are not limited to: (1) the Timed-Up-and-Go (TUG) test – a timed assessment of functional mobility with transfers, walking and a turn; (2) the Berg Balance Scale (BBS) – an assessment of a subject’s balance during performance of 14 tasks; (3) the L Test of Functional Mobility (L Test) – a modified TUG with longer walking distance and additional turn; and (4) the Four Square Step Test (FSST) – an assessment of an individual’s coordination and stability while stepping over low objects forwards, backwards, and sideways.^5,7,20

Outcome measures that have been used to assess the concern of falling in individuals with lower limb amputations include, but are not limited to: (1) the Modified Survey of Activities and Fear of Falling in the Elderly (mSAFE) – a questionnaire that evaluates the avoidance of activities of daily living due to the perceived fear of falling; (2) the Falls Efficacy Scale - International (FES-I) – a 16-item scale that measures an individual’s level of concern of falling when performing physical and social activities; (3) the Consequences of Falling Scale (COF) – this 16-item scale quantifies perceived concerns regarding consequences that may occur after a fall; (4) the Perceived Control Over Falling Scale (PCOF) – a 4-item scale which assesses a subject’s ability to control the environment and mobility; and, (5) the Perceived Ability to Manage Falls Scale (PAMF) – a 5-item scale which assesses the certainty that an individual would be able to manage a fall and find a way to get up.^27,28 Balance confidence tests such as the ABC scale and BBS have also been studied as surrogate measures of the fear of falling in individuals with lower limb amputations.^28,29

Some inconsistencies in the ability of self-reported and performance-based tests to predict fall risk have been reported in the literature for individuals with lower limb amputations,⁵ including, but not limited to: (1) variability in TUG cut-off scores (in seconds);^17,24 (2) variability in the ability of BSS to determine which individuals are at increased or decreased risk of falling;^29,30 and, (3) the paradoxical finding of a greater risk of falling despite higher ABC balance confidence scores in individuals with lower limb amputation compared to the general geriatric population,²⁴ suggesting that patient-perceived performance ability may overestimate actual performance ability.²⁰ In addition to the uncertainty in fall risk outcome measures, the reliability study that examined tests that assess the fear of falling in individuals with lower limb amputations was small and relied on convenience sampling, which may not be representative of the Medicare population.²⁷

Challenges related to assigning functional levels to individuals with lower limb amputation have also been discussed in the literature, due to the lack of a standard objective measure of functional level and the lack of a standard predictive tool for rehabilitation potential.^31-33 Attempts have been made to develop and validate the Amputee Mobility Predictor (AMP) as an objective instrument to predict Medicare functional levels;^34,35 however, the predictive value of the instrument across the Medicare functional classification levels is variable.³¹ Other predictive models of prosthetic mobility potential, based on retrospective data analysis, have been more recently proposed, but further application studies are needed.^36,37

Review of the literature for this summary of evidence will include consideration of the ability of the outcome measures used in the studies to evaluate fall rate, risk of falling, and fear of falling with MPKs compared to NMPKs in Medicare-eligible prosthetic knee users characterized as MFCL-2 (limited community) ambulators. Specifically, potential recall and response bias for self-reported measures, and the reliability and validity of performance-based measures in individuals with lower limb amputations will be assessed.

Food and Drug Administration (FDA) Status

Microprocessor-controlled knees may be classified as either Class I (general controls) devices under 21 CFR §890.3420 (external limb prosthetic component)³⁸ or as Class II (special controls) devices under 21 CFR §890.3500 (external assembled lower limb prosthesis).³⁹ Both classifications are exempt from 510(k) pre-market notification requirements.

Literature Analysis

A retrospective study, by Davie-Smith, et al.,⁴⁰ examined patient-reported and functional outcome measures in a cohort of 31 (per protocol) low-activity participants (defined as either K2 or less active K3 ambulators; mean age: 60 years) with unilateral transfemoral amputation (TFA) when using an MPK compared to a NMPK . Outcome measures were the Health-Related Quality of Life (HR-QoL) survey and gait profile score (GPS) as primary outcomes, and the ABC, PLUS-M, Socket Comfort Score (SCS), self-reported falls, use of walking aids, AMP, L-test, and 2-minute walk test (2MWT) as secondary outcomes. The MPK assigned was determined by the participant’s physician; assigned MPKs were the Kenevo (n = 13), C-Leg 3 (n = 2), C-leg 4 (n = 13), Orion (n = 1), Linx (n = 1), and Rheo (n = 2). After 6 months of MPK use, there were no significant improvements in HR-QoL (p = 0.014), GPS (p = 0.019), PLUS-M (p = 0.056), SCS (p = 0.071), median number of falls, or any 3DGA generated gait specific outcomes (only 15 participants completed the 3DGA). There were significant improvements in ABC score (p < 0.001), L-test time (p < 0.001), walking distance in the 2MWT (p < 0.001), AMP (p < 0.001), and mean number of falls (p < 0.001). Notably, the median number of falls per annum remained unchanged at zero (0) with MPKs compared to NMPKs, suggesting a non-normal distribution of falls in the study population. The change in AMP score resulted in 14 patients being reclassified to a higher MFCL. Limitations of this study include the retrospective design and small cohort size, the heterogeneity in type of MPK, suspension system, foot, and ankle, and the heterogeneity in the amount of physiotherapy or at-home exercises. Additionally, due to the lack of minimum clinically important difference data for most patient-reported and functional outcomes, the true clinical significance in the improvement is not known.

A multi-center, randomized crossover trial, by Lansade, et al.,⁴¹ compared the efficacy of the Kenevo MPK to NMPKs in 35 participants (mean age: 64.5 years; 27 included in the per protocol analysis) with TFA or knee disarticulation, functioning at a moderate activity level [International Classification of Functioning (ICF) d4601 (moving around buildings other than the home) or d4602 (moving around outside the home and other buildings)]. The primary outcome measure was the TUG test; secondary outcome measures were the Locomotor Capability Index (LCI-5), use of walking aids, the Quebec User Evaluation of Satisfaction with Assistive Technology 2.0 (QUEST 2.0) questionnaire, the Medical Outcomes Study Short Form 36 v2 (SF-36v2) physical component and mental component sub-scores, and the number of falls in the last month of the trial. With MPKs, there were statistically significant improvements in balance as per median (Q1-Q3) TUG time (p = 0.001), mobility as per the global and basic LCI-5 score (p = 0.02), satisfaction as per the QUEST 2.0 (p = 0.001), and quality of life per the mental component of the SF-36v2 (p = 0.03). There were no significant differences in advanced LCI-5 score (p = 0.16), the physical component of the SF-36v2 (p = 0.08), use of walking aids (p = 0.97), or the incidence of falls (p = 0.61). No adverse events (AEs) were reported. The study limitations include small cohort size, short follow-up duration, and heterogeneity within the cohort regarding cause of amputations, the type of NMPK used as the comparator, and in the history of additional co-morbidities (e.g., cardiovascular disease, neurological impairment).

Hahn, et al.⁴² performed a retrospective, multi-center, cross-sectional cohort analysis of 1013 data sets to determine if a patient's age (average age: 55.6 years), mobility classification [based on the MOBIS mobility grading system; with MOBIS mobility grade (MG) 2 being similar to MFCL-2], or amputation etiology had an impact on their capability to utilize the functional benefits of an MPK (C-Leg or C-Leg Compact) based on a 1-day trial fitting. Functional outcomes included variance in gait cadence, gait pattern harmonization, relief of the sound limb, reduction of overall effort, divided attention, and safety. Self-reported fear of falling decreased in 82-87% of participants (ranging across age and MG groups), which corresponded to 83% of participants reporting a ‘clear’ or ‘very clear’ increase in perceived safety. Prosthetists reported that 95% of participants had relief of the sound limb, 95% had harmonization of gait pattern, and 93% had the ability to vary gait speed; while 88% of participants reported a reduction in walking effort and 94% reported greater capacity to divide attention. At the end of the trial, 50% [95% Confidence Interval (95% CI): 45-54%] of MG2 participants were re-rated as MG3 after the trial and 22% (95% CI: 18-26%) of MG3 participants were re-rated as MG4. Finally, a correlation analysis was performed, and there was no correlation between age, MG, and vascular disease with an individual’s ability to derive functional benefit from an MPK. The study limitations include that all data was collected from trial fittings in a commercial environment, using no common, validated assessment standard as part of the data collection; thus, this data may not translate to at home use of the prosthesis. Finally, self-report measures, such as fear of falling, may be subject to response bias.

A nonrandomized cross-over study, by Hafner, et al.,⁴³ compared the effects of use of an MPK vs. a NMPK on function and safety in 17 patients, with TFA, classified as MFCL-2 (n = 8) or MFCL-3 (n = 9) (average age MFCL-2: 57.1 years, MFCL-3: 41.9 years; p = 0.05). Functional performance was measured with walking speed and step length on a sloped (19 degree) sidewalk, the Hill Assessment Index (HAI), the Stair Assessment Index (SAI), walking speed during an obstacle course, and accuracy and speed of response to verbal tests administered while participants walked on a busy city block. The PEQ-A was used to assess safety, stability, satisfaction, and quality of life. In the functional outcomes, for both the MFCL-2 and MFCL-3 cohorts, there were statistically significant improvements in the SAI (MFCL-2: p = 0.008, MFCL-3: p = 0.004), hill walking speed (MFCL-2: p = 0.002, MFCL-3: p = 0.017), and obstacle course walking speed (MFCL-2: p = 0.02, MFCL-3: p = 0.007) when using MPKs compared to NMPKs. The MFCL-2 cohort also saw significant improvements in the attention speed test (p = 0.02) and HAI score (p = 0.008) with MPKs. Attention accuracy was not significantly different between the MPK and NMPK in either mobility cohort. On the PEQ-A, the MFCL-3 cohort had a significant improvement in satisfaction (p = 0.002), ambulation (p = 0.01), and utility subscores (p = 0.01); both cohorts reported significant improvement in multitasking while walking when using the MPK (MFCL-2: p = 0.04, MFCL-3: p = 0.03). The MFCL-2 cohort saw significant improvement in the number of self-reported uncontrolled falls (p = 0.01); however, there were no statistically significant improvements in the number of self-reported stumbles, number of semi-controlled falls, or in self-assessed fear outcomes. Finally, four (4) MFCL-2 participants were reclassified as MFCL-3, three (3) MFCL-3 participants were reclassified as MFCL-4, and two (2) MFCL-3 participants were reclassified as MFCL-2. Only change in AMP score was significantly correlated with change in functional level (r_s = 0.62, p = 0.008). This study was limited by the small sample size, lack of randomization and blinding, and use of self-reported fall and stumble rates, which may be subject to recall bias.

An observational study, performed by Kahle, et al.,⁴⁴ compared functional performance of 19 individuals (average age: 51 years; MFCL-2: n = 9, MFCL-3: n = 8, MFCL-4: n = 2), with TFA or knee disarticulation, using an MPK (C-Leg) compared to a NMPK, to determine which population of patients living with lower limb amputation would benefit from use of an MPK. Functional outcomes included self-selected and fastest-possible walking speed on uneven and even terrain, as well as the stair descent test. Self-reported outcomes included the Prosthesis Evaluation Questionnaire (PEQ), knee preference, and number of stumbles and falls. For function outcomes, with the MPK, there were significant reductions in time to complete the following walking tests: 75 m with self-selected walking speed (p = 0.03), 6m (p = 0.001) and 75m (p = 0.005) with fastest-possible walking speed, and 38m with fastest-possible walking speed on uneven terrain (p < 0.001). In self-reported outcomes, there were significant improvements with the MPK in PEQ score (p = 0.007), mean number of stumbles (p = 0.006), and mean number of falls (p = 0.03). Descriptive statistics reported that 63% (12/19) of participants improved their performance composite scores during stair descent with the MPK and that 74% (14/19) of participants would prefer to continue using the MPK. Limitations to this study included the small sample size, heterogeneity in baseline NMPKs used, the mixed cohort of Medicare Functional Classification Levels, potential for recall bias related to self-report of falls and stumbles, and potential for intervention bias as the pre- and post-testing was administered by a single, unblinded rater.

A prospective, non-randomized, crossover clinical trial, by Kaufman, et al.,²⁵ assessed if 23 (per protocol) individuals with unilateral TFA and low mobility, would benefit from using an MPK compared to a NMPK. Functional outcomes were assessed via an activity monitor, while self-reported outcomes of satisfaction and safety were assessed with the PEQ and PEQ-A, respectively. With the MPK, participants had a significant reduction in time spent sitting (p = 0.01) and a significant increase in median activity counts (p = 0.02). There was no significant change in gait complexity with the MPK (p = 0.35). For safety and satisfaction, with the MPK, there was a statistically significant reduction in median number of falls per person per month compared to baseline (p = 0.01) and a significant improvement in satisfaction on the PEQ (p < 0.01). Upon return to the NMPK, the median number of falls increased to 3 falls per person per month, and patients reported a greater fear of falling. Limitations of this study included the small sample size, potential recall and response bias due to use of patient reported falls as a measure of safety, and potential bias due to missing data secondary to a substantial number of patients (27/50) who were lost to follow-up or refused continued participation.

A prospective, observational study, by Mileusnic, et al.,⁴⁵ examined clinical experiences with the Kenevo MPK in 29 individuals (average age: 63.2 years) with TFA or knee disarticulation and a mobility grade of MFCL-1, MFCL-2, or low MFCL-3. Safety, mobility, and preference were assessed using study-designed self-assessment questionnaires (self-reported measures of satisfaction, fear of falling, stumbles, and falls), the LCI-5, PLUS-M, and Houghton scale (self-assessed measure of prosthetic use). Participants completed baseline testing using their NMPK prior to fitting with the Kenevo and returned after 2 months of MPK use for repeat testing. Data was only included for analysis when data for both visits was available and complete, which ranged between 55-69% of participants, depending on the questionnaire. There were positive trends in fear of falling, rate of falling, and scores on the Houghton scale, PLUS-M, and LCI-5 after participants switched from their NMPK to the Kenevo MPK; however, none reached statistical significance (rate of falling: p = 0.161, n = 12; fear of falling: p = 0.075, n = 12; Houghton scale: p = 0.068, n = 11; PLUS-M: p = 0.124, n = 11; LCI-5: p = 0.097, n = 11). The rate of stumbles did significantly decrease (p = 0.044) with the Kenevo MPK (50% of patients (n value not specified) reported never falling with the Kenevo compared to 8% with their NMPK). The number of subjects who reported never falling increased from 45% with their old prosthesis to 72% with the Kenevo (p = 0.161, n = 12). Self-reported fear of falling improved in 50% and worsened in 8% of participants with the Kenevo (n = 12). Limitations of this study included the observational design, small sample size, completeness of data, mixed MFCL study population, and use of self-report of fall data, which may have been affected by recall and response bias.

Hahn, et al.³¹ performed a systematic review and meta-analysis (SRMA) which focused on the effects of use of MPKs on safety, function, and patient-reported outcomes in individuals with lower limb amputations classified as limited community ambulators (MFCL-2). Papers were included in this analysis if they were randomized or non-randomized trials comparing MPK to NMPK use, included limited community ambulators as a primary group/separate statistics, and reported their results with validated measures of safety, function, mobility, or patient-self-reported. There were 15 publications that met inclusion criteria with 2,366 total participants (range of mean ages: 54.1 to 69 years), including 704 participants classified as MFCL-2. When looking at walking performance with an MPK, there was significant improvement in walking speed (5 studies), slope ambulation (3 studies), stair/uneven terrain mobility (2 studies), and activities of daily living (ADL) and multitasking ability (1 study each). After switching from a NMPK to an MPK, 5 studies reported that approximately 50% of subjects increased from MFCL-2 to MFCL-3. Seven (7) studies reported improvements in patient-reported mobility and one (1) study reported improvement in quality of life. For the meta-analysis, both the fixed effect models and the random effects models showed that the standardized mean differences (SMD) favored MPK over NMPK in fall reduction (p < 0.01), fear of falling (p < 0.01), TUG completion time (p = 0.04), walking speed (p < 0.01), patient-reported ambulation PEQ (p < 0.01), and utility PEQ (p < 0.01). None of the included studies reported an outcome measure where NMPK use had a significant benefit over MPK use. Limitations of this SRMA include the high dropout rates in some of the included studies and heterogeneity in clinical outcomes evaluated across the studies, which lead to small sample sizes for each of the outcomes. Additionally, generalizability to the Medicare-aged population may be limited, as only 5/15 studies had an average participant age that was inclusive of this population.

Jayaraman, et al.⁴⁶ performed a 13-month, longitudinal, randomized, crossover clinical trial to determine if MPKs compared to NMPKs improved safety and performance (e.g., walking speed and balance) in 10 participants (average age: 63 years) with unilateral TFA, secondary to vascular disease or diabetes, who are classified as limited community ambulators (MFCL-2). Performance-based outcome measures included the 10-meter walk test (10MWT), 6-minute walk test (6MWT), BBS, FSST, TUG, and AMP with prosthesis (AMPPro). Patient-reported safety outcome measures were the Modified Falls Efficacy Scale (MFES) and the PEQ-A. In an a priori defined post-hoc analysis, based on two-way repeated measures ANOVA methodology, there was significant improvement in the 10MWT when using the MPK compared to baseline in both speed (p = 0.008) and time (p = 0.046), but no significant difference in either speed or time when comparing the NMPK to baseline (p > 0.05). There were also significant improvements in AMPPro scores in post-hoc testing when using both the MPK (p = 0.018) and NMPK (p = 0.03); however, the change did not bring participants into the K3 AMPPro score range for either intervention. Participants self-reported significant improvements in the PEQ-A when using the MPK compared to baseline (p = 0.008), but not when using the NMPK compared to baseline. Finally, there was significant improvement in the MFES when comparing MPK to baseline (p = 0.003), but not when comparing NMPK to baseline (p > 0.05). No statistically significant changes were observed in the 6MWT, BBS, FSST, or TUG with a two-way repeated measures ANOVA. However, when MPK data from the present study was compared to previously published averages for K3 ambulators, 66% of participants improved their gait speed to above a standard K3 ambulator, and 50% of participants improved their BBS scores into a range indicative of a standard K3 ambulator. The limitations to this study include the small sample size (data indicate only 9/10 data sets were analyzed) and the change in prosthetic foot (which may have confounded some of the observed benefits).

Campbell, et al.⁴⁷ conducted a retrospective analysis, on 602 data sets, which compared functional mobility, quality of life, satisfaction with amputee status, and rate of injurious falls (resulting in a clinic/hospital visit) across four MPKs: C-Leg, Orion, Plié, and Rheo (178 participants each used C-Leg, Orion, and Plié; 68 used Rheo; average age: 56.95 to 61.23). All participants were MFCL-3 or MFCL-4. Outcomes included the PLUS-M to assess mobility and the PEQ to assess quality of life and satisfaction. Additionally, 419 participants were included in a fall analysis; 10% reported an injurious fall in the previous 6 months that resulted in a clinic or hospital visit, but there was no significant difference in fall rate between the 4 MPKs (p = 0.171). When compared to NMPK historical benchmark data, C-leg (p < 0.001) and Orion (p = 0.037) users had significantly fewer injurious falls. When participants were grouped by age, there were statistically significant declines in mobility associated with age based on PLUS-M in C-Leg and Plié users; however, there was no statistically significant age-based PLUS-M differences in Rheo or Orion users. Finally, per PEQ survey responses, there was no statistical difference in satisfaction or quality of life across all MPKs. Limitations of this study included its retrospective observational design, use of only patient-reported outcome measures, unequal sample size of Rheo participants (potential selection bias), no standardization of duration of experience with MPK, exclusion of MFCL-1 and -2 participants (indirectness of study population), and inclusion of only falls that resulted in a clinic/hospital visit, which may under-represent the total number of falls.

A randomized crossover trial, by Theeven, et al.,⁴⁸ assessed the effect of switching to an MPK on functional performance of ADLs in 28 (per protocol) individuals (average age: 59.1 years) with unilateral TFA or knee disarticulation classified as MFCL-2. Due to the heterogeneity (i.e., variability in type and severity of comorbidities) of the MFCL-2 population, this study also aimed to determine if these within-group differences might hinder the detection of the effects of using an MPK and to determine if only a subpopulation (high, intermediate, and low activity levels) of individuals classified as MFCL-2 would derive benefit from its use. Functional performance was measured using the investigator-developed Assessment of Daily Activity Performance in Transfemoral Amputees (ADAPT) test in which performance time and perceived level of difficulty were recorded for 17 simulated daily activities. The 17 tasks were divided into 3 activity subsets (AS): AS₁ (standing activities that required balance), AS₂ (activities that required sitting down and standing up), and AS₃ (ambulation activities that rely upon prosthetic-related skills). At baseline, participants in the high and intermediate activity group performed AS₁ (p = 0.001 and p = 0.007, respectively) and AS₂ (p = 0.003 and p = 0.015, respectively) tasks significantly faster than the low activity group. There was no statistical difference between any activity groups in the AS₃ tasks, and a significant difference between the high and intermediate activity groups was only observed in the AS₂ tasks (p = 0.013). When comparing all participants performance with the C-Leg (MPK_A) and the C-Leg Compact (MPK_B) vs. NMPK, there was a significant decrease in time needed to complete AS₁ tasks (MPK_A: p = 0.0001 and MPK_B: p = 0.002); and, the difficultly of tasks in the AS₂ and AS₃ categories was perceived as significantly less difficult with MPK_A (AS₂: p = 0.023 and AS₃: p = 0.008) but not with MPK_B. For the high and intermediate activity groups, there was a significant decrease in time needed to complete AS₁ tasks with both MPK_A (p = 0.010 and p = 0.004, respectively) and MPK_B (p = 0.019 and p = 0.008, respectively). For only the intermediate activity group, AS₂ task time was significantly lower with MPK_A (p = 0.016). There was no statistically significant time difference in AS₃ tasks for any group. Participants in the low activity group saw no significant time difference in any tasks with any prosthetic knee. At the end of the study, 21 (high = 10, intermediate = 7, low = 4) participants indicated preference for MPK_A, 7 (high = 2, intermediate = 3, low = 2) for MPK_B, and 1 (intermediate) for the NMPK. Limitations of this study included a small sample size, use of an unvalidated measure of functional performance, and short duration of follow-up.

Evidence Based Guidelines

Amputation and prosthetics of the lower extremity: The Dutch evidence-based multidisciplinary guideline- 2020⁴⁹

Summary of guidelines (in relevant part):

The conclusions for the a priori-defined outcome were as follows:

• Compared with conventional prosthetic knees, autoadaptive knees may result in lower energy consumption during ambulation at a normal speed (GRADE: low) and improved mobility (GRADE: low).
• It is unclear whether autoadaptive knees are associated with differences in risks of falling, balance, level of physical function, user satisfaction, and gait parameters (GRADE: very low).
• It is unclear whether actuated knees or feet are associated with differences in energy consumption, risks of falling, balance, level of physical function, user satisfaction, and gait parameters compared with conventional knee and foot units (GRADE: very low).

Recommendation:

• Consider the use of autoadaptive knees for either persons with increased risks of falling and impaired ambulatory skills or persons using their prostheses intensively, for whom further improvement in physical function or energy consumption is expected.

VA/DoD Clinical Practice Guideline for Rehabilitation of Individuals with Lower Limb Amputations– 2019⁵⁰

Summary of guidelines (in relevant part):

Recommendations:

Pre-Prosthetic Phase:

15. We suggest offering microprocessor knee units over non-microprocessor knee units for ambulation to reduce risk of falls and maximize patient satisfaction. There is insufficient evidence to recommend for or against any particular socket design, prosthetic foot categories, and suspensions and interfaces. [Strength: Weak for]

Developing Prescribing Guidelines for Microprocessor-Controlled Prosthetic Knees in South East England - 2014⁵¹

Summary of guidelines (in relevant part):

Suitability

The patient needs to meet all the following criteria in order to qualify for consideration for an MPK.

1. Activity level

Unilateral amputee K3 or K4 – patient is an active walker with a free knee – or K2 with demonstrable potential to improve to K3 which is later confirmed through a trial with an MPK. Bilateral amputee who is able to walk with a free knee.

2. Mobility level

SIGAM D or above.

3. Amputation level

Unilateral transfemoral;

Hip disarticulation;

Knee disarticulation;

Bilateral lower limb amputee (a major amputation on the contralateral side at or higher than mid-foot level).

4. The patient must demonstrate

Commitment to prosthetic rehabilitation;

Adequate strength and balance to activate the knee unit;

Cognitive reasoning ability to master control, operation and care of the device;

Sufficient cardiovascular abilities to meet the fitness demands of ambulating outdoors with a free knee (only in a unilateral amputees).

Indications

5. Limited community ambulatory. Improved stability in stance demonstrates increased independence, less risk of falls and potential to advance to a less restrictive walking device. This is providing that the patient has sufficient cardiovascular reserve, strength and balance to use the prosthesis and demonstrable potential to return to an active lifestyle and improve their level of activity. Trial is required to prove a significant improvement reflected in reduced care needs or the ability to perform new functions or daily tasks not possible with a non-MPK.

Professional Society Recommendations

N/A

Expert Consensus Documents

Centers for Medicare & Medicare Services Health Technology Assessment: Lower Limb Prosthetic Workgroup Consensus Document⁵²

Microprocessor Knees (in relevant part):

The Workgroup was divided on the quality and strength of the literature pertaining to microprocessor knees (MPKs) for beneficiaries who ambulate at the K2 level. Some argued that the individual articles noted in the literature which discuss this topic, do adequately demonstrate that those who utilize their prosthesis at the K2 level might improve their functional abilities (e.g., walking speed on level and unlevel ground; ramp descent speed, falls, etc.) with MPK technology. Others argued that the studies comprising this literature were significantly flawed (e.g., small sample sizes, attrition, confounders such as training differences, sole use of laboratory studies, significant conflict of interests, etc.). Those arguing the limitations of these studies are aware that these findings may not agree with the conclusions of other federal agencies.

Therefore, the Workgroup acknowledges an amputee functioning at the K2 level may benefit from MPK technology. However, as a population, these individuals cannot be categorically defined for policy purposes. Consequently, the Workgroup recommends that if consideration is to be given to the provision of a microprocessor knee for an individual who currently utilizes his/her prosthesis at the K2 level, the rationale for that component must be justified in a pre-authorization request. To make that request stronger, a trial of usage should be considered by the prosthetist (prior to payment for the component) with pertinent results of that trial (i.e., pre/post data) as they relate to functional health outcomes including, but not limited to, falls/injuries and the accomplishment of activities of daily living / instrumental activities of daily living (ADLs/IADLs), being highlighted in the pre-authorization information. It will be the decision of the pre-authorization team to approve (or not) the request.

Impact Analysis

Kuhlmann et al., 2020⁵³ developed a decision-analytic model that focused on the amputee population, fall events, and prosthesis failure (i.e., the number of prosthesis revisions). Data for the models were collected from publicly accessible databases, published peer-reviewed literature, and data from prosthetic manufacturer Ottobock. The fall events model calculates the number of annual fall-related events among individuals with lower limb amputations requiring a prosthetic knee and with or without Diabetes Mellitus (DM); the model includes annual falls and falls requiring medical care, which are further classified into fatal and non-fatal medical falls. All fall and fall-related medical events are per 1000 person years. The predicted incidence rate of falls was lower in individuals without DM using the C-Leg compared to those using an NMPK (178 vs. 1102 falls, respectively); as well as in individuals with DM using the C-Leg compared to those using an NMPK (203 vs. 1201 falls, respectively). Fall-related fatalities and hospitalizations also decreased in individuals without DM using the C-Leg compared to NMPK (3 vs. 17 fatal falls and 20 vs. 134 hospitalizations, respectively) and in individuals with DM using the C-Leg compared to NMPK (3 vs. 18 fatal falls and 23 vs. 146 hospitalizations, respectively). This study was limited by the lack of long-term data on the risk of falling, and small sample sizes. Additionally, there was indirectness to the main literature analysis, as the results were based on data from a cohort of individuals with mixed MFCLs, stratified based on diabetes status rather than functional level, and the fatal fall probability data came from a general elderly population without amputations.

An analysis by Chen et al., 2018⁵⁴ included a literature review evaluating the impact of MPK vs. NMPK use in individuals functioning at a level of K3 and K4, as well as a cohort-level Markov model for fall rate. Falls were divided into medical (i.e., requiring medical attention) or non-medical, and medical falls were subdivided into minor, major (i.e., requiring admission to a medical facility), or fatal. Data included was from peer-reviewed articles and non-peer reviewed literature, such as technical reports and an expert panel. Data on K2 individuals was only included in the sensitivity analysis. Based on the model, when MPK use is compared to NMPK use, the risk of major injurious falls is reduced by 79% (104 to 22 falls per 1000 person years) and the incidence of minor falls reduced from 78 to 16 falls per 1000 person years. Fall-related deaths per 1000 person years decreased from 14 with NMPK use to 3 with MPK use. Limitations from this study include use of fall data from individuals from the general elderly population without amputations (e.g., medical falls out of all falls), small sample sizes, and limited follow-up time. Additionally, the fall rate model is limited by indirectness, as it did not include data from K2 individuals, only K3 and K4 individuals.

The aim of this summary of evidence was to determine if the use of MPKs with stumble recovery, or similar technology, compared to NMPKs improved the rate of falls, risk of falling, fear of falling, and gait performance in MFCL-2 Medicare beneficiaries with lower limb amputations requiring a prosthetic knee. Studies that were reviewed were analyzed for risk of bias (ROB). For RCTs, ROB was assessed using the Cochrane Collaboration’s tool for assessing risk of bias.^55,56 To evaluate the ROB in non-randomized studies, the ROB in Non-Randomized Studies of Interventions (ROBINS-I) tool was used.⁵⁷ The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach was used as a method of grading the certainty of evidence, which can range from high to very low, and is defined as follows:⁵⁸

Certainty of Evidence

Fall Rate: Low to Very Low

• Number of Falls based on RCTs: Low
• Number of Falls based on observational studies: Very Low
• Fall Rate on a 5-point scale based on an observational study: Very Low
• Number of Uncontrolled Falls based on an observational study: Very Low

Risk of Falling: Low to Very Low

• Timed up and go (TUG) based on RCTs: Low
• BERG balance scale (BBS) based on an RCT: Low
• Four Square Strep Test (FSST) based on an RCT: Low
• Prosthesis Evaluation Questionnaire (PEQ-A) based on an RCT: Low
• Modified PEQ-A based on an observational study: Very Low
• Activities Specific Balance Confidence (ABC) based on an observational study: Very Low
• Prosthetic Limb User Survey of Mobility 12-item Short Form (PLUS-M) based on observational studies: Very Low
• Test of Functional Mobility (L-test) based on an observational study: Very Low

Fear of Falling: Low to Very Low

• Modified Fall Efficacy Scale (MFES) based on an RCT: Low
• Self-reported fear of falling based on observational studies: Very Low
• Customized PEQ-A Addendum based on observational studies: Very Low

Gait Performance: Low to Very Low

• 10-meter walk test (10MWT); 6-minute walk test (6MWT) follow-up: 13 months based on an RCT: Low
• 3D gait analysis generated gait profile score follow-up: 6 months based on an observational study: Very Low
• Gait Complexity Calculation based on an observational study: Very Low
• Gait Harmonizing Scale, Gait Cadence Variance Scale based on an observational study: Very Low
• Stair descent, Uneven Terrain Walking Speed based on observational studies: Very Low
• Function on an incline based on an observational study: Very Low

MPK Comparison in Fall Rate: Low to Very Low

• Assessment of Daily Activity Performance in Transfemoral Amputees (ADAPT) based on an RCT: Low
• Self-reported rate of injurious falls based on an observational study: Very Low

Conclusion

Microprocessor-controlled prosthetic knees use integrated sensors and computers to collect and analyze data to adjust flexion and extension resistance of the prosthetic joint during the swing- and/or stance-phase of the gait cycle in real time. Purported benefits of MPKs compared to NMPKs include improved stability when the user is standing and walking, as well as fall prevention with the addition of technology which can automatically increase resistance in the knee unit to provide support when a stumble is detected.

The use of an MPK compared to a NMPK may reduce the rate of falling, risk of falling and fear of falling, as well as improve gait performance in individuals with lower limb amputations requiring a prosthetic knee who are classified as limited community ambulators (i.e., MFCL-2), based on low to very low certainty evidence. While multiple studies examining these outcomes were limited by their nonrandomized design, small sample sizes, missing data, uncertainty related to the directness of the study cohorts, and/or reliance on outcome measures that are subject to recall or response bias, the conclusions of the studies were consistent, with no studies finding outcomes favoring NMPKs compared to MPKs. Additionally, computer simulated impact modeling suggest a large effect size related to both the incidence of falls and risk of falling in MPK users compared to NMPK users. Also notable, no studies were identified to support that the benefits of MPKs are limited to individuals classified as MFCL-3 and above; however, the currently available literature is insufficient to support extending coverage of MPKs to MFCL-1 beneficiaries. Of the original research analyzed for the Summary of Evidence, only one study included any MFCL-1 participants.

Microprocessor-controlled prosthetic knees may be a viable therapeutic option for some limited community ambulating Medicare beneficiaries with lower limb amputations. Therefore, the criteria in the Lower Limb Prostheses Local Coverage Determination will be expanded to allow coverage of fluid, pneumatic, or electronic/microprocessor control additions for prosthetic knees in MFCL-2 beneficiaries when supporting documentation in the medical record outlines the rationale for selection of the higher-level knee. This documentation must include how the selected knee will improve the beneficiary’s functional health outcomes, will help the beneficiary accomplish their activities of daily living, and that lower-level knee options have been considered and ruled out based on the beneficiary’s individual functional and medical needs.

In addition, for coverage of electronic/microprocessor-controlled knees for MFCL-2 beneficiaries, the MPK provided must be indicated for functional level 2 individuals and include integrated technology that allows the knee to detect when the user stumbles, automatically increases resistance in the knee to provide support for recovery, and potentially prevents a fall. Furthermore, the LCD stipulates that the beneficiary is able to make use of a product that requires daily charging and can understand and respond to alerts/alarms which may indicate knee dysfunction.

Criteria of higher-level foot systems will also be expanded to include MFCL-2 beneficiaries who meet the new coverage criteria for a fluid, pneumatic, or electronic/microprocessor control addition for a prosthetic knee, and who will require a compatible foot.  

Documentation Requirements

Section 1833(e) of the Social Security Act precludes payment to any provider of services unless "there has been furnished such information as may be necessary in order to determine the amounts due such provider.” It is expected that the beneficiary's medical records will reflect the need for the care provided. The beneficiary's medical records include the treating practitioner's office records, hospital records, nursing home records, home health agency records, records from other healthcare professionals and test reports. This documentation must be available upon request.

GENERAL DOCUMENTATION REQUIREMENTS

In order to justify payment for DMEPOS items, suppliers must meet the following requirements:

• SWO

• Medical Record Information (including continued need/use if applicable)

• Correct Coding

• Proof of Delivery

Refer to the LCD-related Standard Documentation Requirements article, located at the bottom of this policy under the Related Local Coverage Documents section for additional information regarding these requirements.

Refer to the Supplier Manual for additional information on documentation requirements.

Refer to the DME MAC web sites for additional bulletin articles and other publications related to this LCD.

POLICY SPECIFIC DOCUMENTATION REQUIREMENTS

Items covered in this LCD have additional policy-specific requirements that must be met prior to Medicare reimbursement.

Refer to the LCD-related Policy article, located at the bottom of this policy under the Related Local Coverage Documents section for additional information.

Appendices


Utilization Guidelines
Refer to Coverage Indications, Limitations and/or Medical Necessity.

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