CG-OR-PR-09 Microprocessor Controlled Knee-Ankle-Foot Orthosis

This document addresses the use of a microprocessor controlled knee-ankle-foot orthosis (for example, the C-Brace^®, Ottobock HealthCare LP, Austin, TX) that provides support for individuals with lower extremity weakness. This microprocessor controlled device is a stance and swing phase control orthosis (SSCO) intended to augment the function of individuals with peripheral or central neurologic conditions that result in weakness or paresis of the quadriceps and/or other knee extensor muscles.

Note: This device should not be confused with microprocessor controlled prosthetic devices, which are intended to replace or compensate for a missing limb or body part. For documents related to microprocessor controlled prosthetic devices see

The use of a microprocessor controlled knee-ankle-foot orthosis is considered not medically necessary when the criteria above have not been met.

The following codes for treatments and procedures applicable to this guideline are included below for informational purposes. Inclusion or exclusion of a procedure, diagnosis or device code(s) does not constitute or imply member coverage or provider reimbursement policy. Please refer to the member's contract benefits in effect at the time of service to determine coverage or non-coverage of these services as it applies to an individual member.

When services are Not Medically Necessary:
For the procedure code listed above when criteria are not met.

More than 1.8 million people in the United States use lower-extremity orthoses. For centuries, individuals with lower-extremity weakness, or specifically quadricep weakness, were prescribed an LKAFO. This device may cause abnormal gait patterns that can contribute to chronic pain, slower gait and decreased mobility (Deems-Dluhy, 2021). Since 1978, SCOs that allow users to flex their knee during the swing phase to prevent abnormal gait patterns have been another option to individuals who suffer from lower limb paresis or paralysis (Pröbsting, 2017). Devices such as LKAFOs and SCOs are limited in function whereas an MPO, such as the C-Brace, uses sensor technology to improve the balance, functional mobility and quality of life in individuals with lower-extremity impairments. The C-Brace combines electronic components with a specialized orthotic brace that provides support for individuals with conditions such as lesions of the femoral nerve, incomplete spinal cord injury, as well as orthopedic conditions that result in uncontrolled knee flexion, failed knee joint replacement and knee joint derangement. The C-Brace’s stance and swing phase of the gait cycle is controlled hydraulically with microprocessor sensor technology that receives information from the electronic sensors 100 times per second. This device stabilizes the knee in the sagittal plane and mimics the physiologic function of the quadriceps muscle which supports the user during the entire gait cycle. With the use of this microprocessor-controlled leg orthotic, an individual is able to obtain a closer physiological value of walking compared to the functionality of conventional paralysis orthoses that are limited to releasing and locking the knee joint.

The lack of functional ability of individuals with conditions that result in weakness or paresis of the quadriceps and/or other knee extensor muscles can have a significant impact on ADLs. The Manual muscle testing (MMT) Grading system is used by practitioners for the evaluation of strength of individual muscles or muscle groups. This grading system has a scale of 0 to 5 and the purpose of this grading system is to ensure accurate, consistent interpretation of MMT findings. The following classifications are used to determine strength and grade:

Level 0:           No visible or palpable contraction
Level 1:           Palpable muscle contraction but no joint movement, gravity eliminated
Level 1+:         Less than or equal to half active range with gravity eliminated
Level 2-:          Movement greater than half range but less than full range, gravity eliminated
Level 2:           Full range of motion (ROM), gravity eliminated, cannot take resistance nor initiate against gravity
Level 2+^:Completes less than or equal to half range actively against gravity and completes full ROM with gravity eliminated
Level 3-:          Greater than half range but less than full range in antigravity position
Level 3:           Full ROM, antigravity, cannot take resistance
Level 3+:         Full ROM against gravity with slight resistance
Level 4-:          Full ROM against gravity with mild resistance
Level 4:           Full ROM against gravity with moderate resistance
Level 4+:         Full ROM against gravity with slightly greater than moderate resistance
Level 5:           Normal, maximal resistance

According to the U.S. Food and Drug Administration (FDA), the C-Brace is classified as a Class I device and exempt from the premarket notification 510(k) requirements as well as the Medical Device Good Manufacturing Practices (GMPs). A device may be exempt from 510(k) requirements if the FDA determines that a 510(k) is not required to provide reasonable assurance of safety and effectiveness for the device (FDA, 2019).

Traditionally, individuals who require the use of an orthosis due to a condition that results in weakness or paresis of the lower extremity have been prescribed and fitted with other types of orthoses such as an LKAFO or an SCO. The C-Brace and similar devices utilize microprocessor-controlled hydraulic units to potentially provide stability and dynamic movement improvements to leg orthosis-dependent individuals.

Individuals with lower limb weakness or paralysis may benefit from the use of a KAFO. There are different types of KAFOs and the mechanism of action of the KAFO that is prescribed depends on the individual’s need and the remaining muscle function (Pröbsting, 2017). A stance controlled orthosis (SCO) is a form of KAFO which uses various technical switching mechanisms to allow locking the orthotic knee joint during stance for safe standing and walking as well as unlocking it at the end of the stance. Although this type of device allows an individual to flex their knee during the gait cycle, it is has been reported to be limited in function and safety due to its inconsistent control of the stance knee on stairs, ramps and uneven ground (Deems-Dluhy, 2021). The C-Brace, which uses signal-processing algorithms, supports walking with a wide variety of different gait velocities. This type of orthosis may be appropriate for individuals who meet specific criteria for fitness, health, and daily utilization expectations. According to the manufacturer, there are prerequisites that an individual must meet before an individual can be considered a candidate for the C-Brace: able to fully stabilize their trunk and to stand when knee flexion is locked, hip extensor and flexor strength available to permit the controlled swing-through of the affected leg, or the ability to advance the limb by compensatory trunk movement in the absence of such strength, and body weight of 275 pounds or less. Unlike the KAFO and SCO, the C-Brace controls knee flexion during weight bearing and dynamic swing control (Pröbsting, 2017).

Deems-Dluhy (2021) evaluated the potential of the C-Brace compared to an SCO and conventional KAFO over a period of a month. This randomized controlled trial (RCT) included 18 participants who actively used a unilateral KAFO and used the following inclusion criteria: 18-80 years of age, regular and compliant use of a unilateral KAFO or SCO for impairment due to neurologic or neuromuscular disease, orthopedic disease, or trauma, ability to demonstrate a gait pattern to use the SCO and C-Brace, cognitive ability to understand and willingness to provide informed consent and follow the study protocol. Exclusion criteria included participants with ankle passive range of motion less than two degrees or knee flexion contracture or alignment resulting in the inability to actively use the study device, weight greater than 275 pounds, unstable neurologic or cardiovascular or pulmonary disease, or cancer, and participation in physical therapy specific to orthotic and gait training within 1 month of enrollment. Significant changes were observed in participants’ self-selected gait speed (p=0.023), Berg Balance Scale (BBS) results (p=0.01), Functional Gait Assessment (FGA, p=0.002), and Stair Assessment Index (SAI, p<0.001) between baseline and post-C-Brace assessment. Similar significant differences were seen when comparing post- C-Brace with post-SCO data. During the 6-minute walk test (6MWT), persons using the C-Brace walked significantly longer (p=0.013) than when using their baseline device. Participants reported higher quality of life scores in the Orthotic and Prosthetic User’s Survey (OPUS) (p=0.02) and physical health domain of the World Health Organization Quality of Life (WHOQOL)-BREF (p=0.037) after using the C-Brace. Participants reported fewer falls when wearing the C-Brace vs. an SCO or locked knee-ankle-foot orthosis (LKAFO). The study concluded that the C-Brace may contribute to improved quality of life and health status of individuals with lower extremity impairments by providing the ability to have better walking speed, endurance, and functional balance.

Pröbsting and others (2017) performed a study to evaluate the potential benefits of a C-Brace vs. SCO and LKAFO in activities of daily living (ADL). The study design was a survey of 13 lower limb orthosis users before and after fitting of a C-Brace. All participants were dependent on KAFOs. Only 1 participant needed orthoses for both legs. Inclusion criterion was individuals had to have used their previous orthosis for at least 6 months prior to enrollment in this study. Based on the results of the self-reported Orthosis Evaluation Questionnaire and the Activities of Daily Living Questionnaire (ADL-Q), participants rated the activities in the domains of family and social life (p=0.01) and mobility and transportation (p=0.002) significantly easier to perform with the C-Brace vs. their standard device. In the categories sports (p=0.02) and ‘other activities’ (p=0.03), a significant improvement with the C-Brace was reported vs. their standard device. No significant difference was seen in the domain personal hygiene and dressing. In the subgroup of participants who had previously used SCOs, use of a C-Brace resulted in a significant improvement in the category of mobility and transportation (p=0.02). Similarly, in the subgroup of participants who had previously used LKAFOs, significant improvements were reported post-C-Brace use in the categories family and social life (p=0.04), mobility and transportation (p=0.04), and other activities (p=0.04). Perceived comparative safety was reported as improved was reported by 59% of subjects with the microprocessor controlled orthoses vs. a standard device. The authors concluded that the C-Brace may facilitate an easier, more physiological, and safer execution of many ADLs compared to traditional leg orthosis technologies.

Schmalz and colleagues (2016) conducted a study to compare the functionalities of conventional KAFOs and the C-Brace. The study enrolled 6 KAFO users who were fitted with a C-Brace for periods between 7 and 30 weeks. Inclusion criteria for the participants in this study were ages between 18-70 years and dependency on a KAFO for walking. Individuals were excluded from participation if they were using additional walking aids to ambulate on level ground. MMT using the Janda scale from 0 to 5 demonstrated significant variation in the strength of the muscles of the affected lower limb. Biomechanical tests were conducted with the participants using their previous orthoses and the C-Brace, including level walking, ramp or stair decent when possible, and step over step movement pattern. Once fitted with the C-Brace, participants used it in their everyday routine for at least 7 weeks. On level surfaces walking, results did not show any significant differences between the previous groups. Step length asymmetry differences noted with their KAFO were resolved in one subject while using the C-Brace. All participants were able to descend a ramp using the natural step-over-step technique with the C-Brace. Only 1 needed the handrail vs. all using the handrail with their standard device. No individuals were able to descend stairs in a natural step-over-step technique with the standard orthoses. However, all individuals were able to descend stairs using the step-over-step technique with the use of the handrail while using the C-Brace. The results of this study indicated that individuals were able to use the C-Brace lower limb orthosis even if they are not able to use an SCO.

Ruetz (2023) reported the results of a randomized, controlled, cross-over clinical trial involving 102 experienced KAFO users at risk of falling who were assigned to 3 months using either a standard KAFO or the C-Brace before switching devices for an additional 3-month trial. Inclusion criteria were > 18 years of age, at least 3 months of uni- or bilateral KAFO use, Berg Balance Scale (BBS) score < 45, minimum hip strength of grade 3 for bilateral users or the ability to swing the orthotic leg forward with trunk movement, potential to use the C-Brace successfully, ability to recognize low battery indicators from the device, and commitment to use the C-Brace for a minimum of 1-2 hrs./5 days a week. Exclusion criteria were, no prior use of a lower limb orthosis, prior use of a C-Brace, weight > 125 kg, lower limb amputation, hip or knee contracture > 10°, bowed legs or knock knees > 10° that cannot be corrected, uncontrolled moderate to severe spasticity, limb length discrepancy > 15 cm, known vertigo, or history of falls. A total of 69 participants (67.6%) completed the full trial and were included in the per-protocol (PP) analysis. The intent-to-treat (ITT) analysis included the full 102 participants. After a 3-month trial, BBS results indicated a significant improvement with the C-Brace vs. the standard device group in both the PP and ITT analyses (p<0.00001 for ITT and p<0.00006 for PP). Similar findings were reported for falls (p<0.002 for ITT and p<0.0005 for PP), Dynamic Gait index (DGI, p<0.005 for ITT and p<0.00001 for PP), Activity-specific Balance Confidence (ABC, p<0.005 for ITT and p<0.0001 for PP), and SAI (p<0.006 for ITT and p<0.008 for PP). Results were significantly improved in the C-Brace vs. the standard device group in the ITT but not the PP analysis in several measures, including the OPUS Lower Extremity Functional Status score (p<0.00019 for ITT and p<0.06 for PP) and the Reintegration into Normal living index (RNLI, p<0.08 for ITT and p<0.042 for PP). The opposite was found for the WLQ-25 Physical (p<0.281 for ITT and p<0.039 for PP) and the EQ-5D5L Utility (p<0.15 for ITT and p<0.037 for PP). No differences between groups were reported for the 6MWT (p<0.58 for ITT and p<0.55 for PP). The authors concluded that the C-Brace provided significant benefits over standard KAFO devices with regard to falls and overall mobility.

Based on the peer-reviewed literature, use of the C-Brace leg orthosis has been shown to provide carefully selected individuals better walking speeds, endurance and functional balance with the device as compared to a standard KAFO device. Due to technological advancements of leg orthoses, individuals with lower extremity impairment may have easier execution of many ADLs and achieve improved quality of life.

Knee Ankle Foot Orthosis (KAFO): A long-leg orthosis that spans the entire leg and is provided to compensate for muscle weakness, paralysis, or skeletal problems which cause lower limb instability.

Locked Knee Ankle Foot Orthosis (LKAFO): Knee-ankle-foot-orthosis with a locked orthotic knee joint.

Manual Muscle Test (MMT): A procedure for the evaluation of strength of individual muscle or muscles group, based upon the effective performance of a movement in relation to the forces of gravity or Manual Resistance through the available Range of motion (ROM).

Orthosis: An orthopedic appliance or apparatus used to support, align, prevent, or correct deformities, or to improve function of movable parts of the body. These types of devices are not prosthetic devices, which are intended to replace or compensate for a missing limb or other body part.

Stance Control Orthosis (SCOs): An orthosis which uses various technical switching mechanisms to allow locking the orthotic knee joint during stance for safe standing and walking as well as unlocking it at the end of the stance phase to allow for a free swing phase.

The use of specific product names is illustrative 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.

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Subject: Microprocessor Controlled Knee-Ankle-Foot Orthosis
Guideline #: CG-OR-PR-09	Publish Date: 10/01/2024
Status: Reviewed	Last Review Date: 08/08/2024

HCPCS
L2006	Knee ankle foot device, any material, single or double upright, swing and/or stance phase microprocessor control with adjustability, includes all components (e.g., sensors, batteries, charger), any type activation, with or without ankle joint(s), custom fabricated

ICD-10 Diagnosis
	All diagnoses

Status	Date	Action
Reviewed	08/08/2024	Medical Policy & Technology Assessment Committee (MPTAC) review. Revised Discussion and References sections.
New	08/10/2023	MPTAC review. Initial document development. Moved content of OR-PR.00007 to new clinical utilization management guideline document with the same title.