Lower Limb Prostheses

Khan, et al. (2019) reported on a study where participants with chronic (> 1 yr) motor complete or incomplete spinal cord injury, who were primarily wheelchair users, were trained to walk in the ReWalk powered exoskeleton for 12 weeks. Measures were taken before, during, immediately after, and 2-3 months after training. Measures included walking progression, sitting balance, skin sensation, spasticity, and strength of the corticospinal tracts. Twelve participants were enrolled with 10 completing training. The investigators reported that the progression in training required about 45 sessions to reach 80% of final performance in training. By the end of training, participants walked at speeds of 0.28-0.60 meters per second, and distances of 0.74-1.97 km in 1 hour. The effort of walking was about 3.3 times that for manual wheelchair propulsion. One non-walker with an incomplete injury became a walker without the ReWalk after training. The investigators reported that sitting balance was improved in some, as seen from the limits of stability and sway speed. Neuropathic pain showed no long term changes. Change in spasticity was mixed with suggestion of differences between those with high versus low spasticity prior to training. The strength of motor pathways from the brain to back extensor muscles remained unchanged. Minor adverse events were encountered by the participants and trainer (skin abrasions, non-injurious falls). The majority of participants could walk on uneven surfaces outdoors. Some limitations were encountered in home-like environments.

Manns, et al. (2019) evaluated the expectations and experiences of persons with spinal cord injury, training with the ReWalk exoskeleton. A qualitative research design with individual interviews was used. Eleven participants with spinal cord injury, taking part in 12 weeks of 4 times weekly training using the ReWalk, were interviewed before, immediately after, and 2 months after training. Interviews were audio recorded and transcribed verbatim. A six stage approach to thematic analysis was used. The investigators found that the theme consistently expressed was the exoskeleton allowed participants to do everyday activities, like everyone else, such as looking people in the eye or walking outside. Their experiences were captured in three categories: 1) learning, a description of both expectations for learning and perspectives on how learning occurred; 2) changing, perspectives on perceived changes with training; and 3) contributing, which captured participant perspectives on contributing to research, including the giving of direct feedback regarding the exoskeleton (i.e., what worked and what could be changed).

Guanziroli, et al. (2019) assessed if walking ability of motor complete spinal cord injury (SCI) patients at thoracic or lower level, using a wearable powered exoskeleton (ReWalk), can be influenced by different exoskeleton software control. Fifteen SCI chronic patients (4 females and 11 males) were recruited and divided in two groups: group 1, trained with the first software generation of ReWalk, and group 2, trained with the second software generation, a software upgrade of the previous version. Subjects were trained during three 60-minute sessions a week, during at least eight weeks using ReWalk, a wearable lower limb powered exoskeleton that allows thoracic or lower level motor-complete individuals with SCI to walk, stand, sit and climb/descend stairs. Outcome measures, collected at the end of the training period wearing the exoskeleton, were: 6-min Walking Test, 10-m Walking Test, and the time necessary to pass from sitting to standing and start to walk (STS-time). For each group Pearson Coefficient was calculated to explore correlations between the subjects' characteristics and gait performance reached at the end of the training period. Group 1 showed correlation between performances and weight, height, neurological lesion level, while group 2 showed no correlation between performances weight and height, but correlation only with neurological lesion level. Group 2 covered more distance in 6 min (+124.52%) and required less time (-70.34%) to perform 10 mtWT and to STS-time (-38.25%) if compared to group 1.

Muijzer-Witteveen, et al. (2018) examined which information would be most important to receive while using an exoskeleton and how this feedback should be provided. To investigate the preferences of users of an exoskeleton, a questionnaire was filled out by 10 SCI subjects who underwent a training program with a commercial exoskeleton (ReWalk). The questionnaire consisted of questions about the use of the exoskeleton to identify which information is missing and which instructions from the therapists were needed to be able to control the exoskeleton. The second part of the questionnaire focused on the possibilities of sensory feedback and preferences for stimulation methods (auditory, vibrotactile or visual) and feedback timing (discrete or continuous) were investigated. Furthermore, six options for feedback parameters (step initiation, continuous and discrete gait phases, foot position and mediolateral and anteroposterior weight shift) were proposed and the respondents were asked to indicate their preferences. Three feedback parameters (feedback about mediolateral and anteroposterior weight shift and feedback about step initiation) were considered  as possibly helpful by the respondents. Furthermore, there were slight preferences for the use of vibrotactile (over auditory and visual) and discrete (over continuous) feedback.

van Dijsseldonk, et al. (2017) sought to develop and test the hierarchy and reliability of a framework for measuring the progress in the ability to perform basic and advanced skills. Twelve participants with paraplegia were given twenty-four training sessions in 8 weeks with the Rewalk-exoskeleton. During the 2nd, 4th, and 6th training week the Intermediate-skills-test was performed consisting of 27 skills, measured in an hierarchical order of difficulty, until two skills were not achieved. When participants could walk independently, the Final-skills-test, consisting of 20 skills, was performed in the last training session. Each skill was performed at least two times with a maximum of three attempts. As a reliability measure the consistency was used, which was the number of skills performed the same in the first two attempts relative to the total number. Ten participants completed the training program. Their number of achieved intermediate skills was significantly different between the measurements XF2(2) = 12.36, p = 0.001. Post-hoc analysis revealed a significant increase in the median achieved intermediate skills from 4 [1-7] at the first to 10.5 [5-26] at the third Intermediate-skills-test. The rate of participants who achieved the intermediate skills decreased and the coefficient of reproducibility was 0.98. Eight participants met the criteria to perform the Final-skills-test. Their median number of successfully performed final skills was 16.5 [13-20] and 17 [14-19] skills in the first and second time. The overall consistency of >70% was achieved in the Intermediate-skills-test (73%) and the Final-skills-test (81%). Eight out of twelve participants experienced skin damage during the training, in four participants this resulted in missed training sessions. The framework proposed in this study measured the progress in performing basic and advanced exoskeleton skills during a training program. The investigators concluded that the hierarchical ordered skills-test could discriminate across participants' skill-level and the overall consistency was considered acceptable.

Fritz, et al. (2019) provided an overview of the features and limitations of the four robotic exoskeleton products (EKSO Bionics, ReWalk, Rex Bionics, and Indego) that are currently being used in in the United States in rehabilitation settings.  The authors stated that available devices appear to be better suited for rehabilitation settings than for home use. Device weight, the need for upper extremity supports, supervision requirements, and a limited range of movements are all issues that limit functionality and restrict opportunities for using such devices in real-world contexts. Designing the next generation of exoskeletons to be more useful in everyday life will require further collaboration among engineers, clinicians, and patients. The authors stated that further development of exoskeleton technologies is warranted to improve the devices for real-world use.

He, et al. (2017) noted that, in 2014, the US Food and Drug Administration approved marketing of the ReWalk Personal Exoskeleton as a class II medical device with special controls. Since then, Indego and Ekso have also received regulatory approval. With similar trends worldwide, this industry is likely to grow rapidly. On the other hand, the regulatory science of powered exoskeletons is still developing. The type and extent of probable risks of these devices are yet to be understood, and industry standards are yet to be developed. To address this gap, Manufacturer and User Facility Device Experience, Clinicaltrials.gov, and PubMed databases were searched for reports of adverse events and inclusion and exclusion criteria involving the use of lower limb powered exoskeletons. Current inclusion and exclusion criteria, which can determine probable risks, were found to be diverse. Reported adverse events and identified risks of current devices are also wide-ranging. In light of these findings, the authors compared current regulations, standards, and regulatory procedures for medical device applications in the USA, Europe, and Japan. The authors stated that there is a need to raise awareness of probable risks associated with the use of powered exoskeletons and to develop adequate countermeasures, standards, and regulations for these human-machine systems. With appropriate risk mitigation strategies, adequate standards, comprehensive reporting of adverse events, and regulatory oversight, powered exoskeletons may one day allow individuals with gait disabilities to safely and independently ambulate.

The Ekso (formerly eLegs) system is another powered exoskeleton device for patients with paraplegia or lower-extremity paresis due to neurologic conditions, including spinal cord injuries, multiple sclerosis, amyotrophic lateral sclerosis, or Guillain-Barré syndrome (ECRI, 2013). It incorporates technology similar to that of the ReWalk system. The 45 lb Ekso system is based on the Human Universal Load Carrier that the U.S. military uses; it is a motorized exoskeleton designed to allow users to carry up to 200 lb continuously for several hours over any terrain. The manufacturer states that transfer to and from a patient’s wheelchair and the powered exoskeleton device takes less than 5 minutes and that the user requires little to no assistance. The company estimates the battery life for this device to be 3 hours.

The Ekso robotic exoskeleton is a motorized orthosis device for use in rehabilitation activities for people who have weak or paralyzed legs and sufficient arm strength to use crutches (NICE, 2017). It is intended to help people to relearn to stand and walk. The innovative aspect of the Ekso GT robotic exoskeleton is the SmartAssist software that is incorporated in the device (NICE, 2017). This allows physiotherapists to set the power for each leg independently to best suit the user. Multiple patients can use each Ekso robotic exoskeleton, with it being adapted to their specific needs. The intended place in therapy would be instead of, or in addition to, existing rehabilitation activities including physiotherapy, exercise, strength training, walking therapies with or without support, and functional electrical stimulation. 

A MedTech Innovation Briefing (NICE, 2017) stated that the key points from the evidence summarized in this briefing are from 1 systematic review and 5 case series, involving a total of 41 patients in a rehabilitation setting. After using Ekso, these patients were able to walk without assistance from physiotherapists and their walking speed and distance increased. No serious adverse events were reported. The briefing stated that key uncertainties around the evidence are that the included studies were small and non-comparative. The briefing stated that the resource impact is currently unclear because of a lack of evidence. 

Kolakowsky-Hayner et al conducted a prospective pilot study in a spinal cord injury rehabilitation center outpatient gym to evaluate feasibility and safety of Ekso to aid ambulation in individuals with SCI.  Eight individuals, at least 18 years of age, with complete T1 SCI or below, within 2 years of injury, completed initial inpatient rehabilitation.  All participants signed informed consent, had been cleared from requiring spinal orthoses, met inclusion criteria, and were pre-screened based on device requirements and medical stability.  The subjects received 6 weekly sessions with graduated time and less assistance in the Ekso device.  Outcome measures included skin evaluation, blood pressure, pain level, spasticity, time and level of assistance needed to transfer into and don device; time ambulating; time up in device; assistive devices used during ambulation; step length; distance walked; level of assistance during use; losses of balance; number of falls and level of assistance needed to doff and transfer out of device.  The investigators reported no major skin effects, minimal pain reports, no known fractures, swelling, or other adverse events.  Level of assistance ranged from dependent to moderate independent, average set up time was 18.13 minutes, and loss of balance and falls were infrequent.  The investigators concluded that bionic exoskeletons such as Ekso are safe for those with complete thoracic SCI in a controlled environment, in the presence of experts, and may eventually enhance mobility in those without volitional lower extremity function.  There appears to be a training effect in the device but further trials are needed.  The investigators stated that future studies of bionic exoskeletons as gait training devices are warranted, and that future studies of bionic exoskeletons as a clinical tool to alleviate secondary complications should be considered.

Kozlowski et al (2015) sought to quantify the time and effort required by persons with SCI to learn to use the Ekso exoskeleton for assisted walking.  A convenience sample was enrolled to learn to use the first-generation Ekso powered exoskeleton to walk.  Participants were given up to 24 weekly sessions of instruction.  Data were collected on assistance level, walking distance and speed, heart rate, perceived exertion, and adverse events.  Time and effort was quantified by the number of sessions required for participants to stand up, walk for 30 minutes, and sit down, initially with minimal and subsequently with contact guard assistance.  Of 22 enrolled participants, 9 screen-failed, and 7 had complete data.  All of these 7 were men; 2 had tetraplegia and 5 had motor-complete injuries.  Of these, 5 participants could stand, walk, and sit with contact guard or close supervision assistance, and 2 required minimal to moderate assistance.  Walk times ranged from 28 to 94 minutes with average speeds ranging from 0.11 to 0.21 m/s.  For all participants, heart rate changes and reported perceived exertion were consistent with light to moderate exercise.

In a case series from an academic research center, Kressler et al (2014) explored responses to overground bionic ambulation (OBA) training with the Ekso exoskeleton three days per week for 6 weeks from an interdisciplinary perspective including key components of neuromuscular activation, exercise conditioning, mobility capacity, and neuropathic pain.  Persons (n = 3; 2 men, 1 woman) aged 26 to 38 years with complete spinal cord injury (SCI) (American Spinal Injury Association Impairment Scale grade A) between the levels of T1 and T10 for 1 year or longer. To obtain a comprehensive understanding of responses to OBA, an array of measures were obtained while walking in the device, including walking speeds and distances, energy expenditure, exercise conditioning effects, and neuromuscular and cortical activity patterns.  Changes in spasticity and pain severity related to OBA use were also assessed.  With training, participants were able to achieve walking speeds and distances in the OBA device similar to those observed in persons with motor-incomplete SCI (10-m walk speed, 0.11 to 0.33 m/s; 2-min walk distance, 11 to 33 m).  The energy expenditure required for OBA was similar to walking in persons without disability (i.e., 25 % to 41 % of peak oxygen consumption).  Subjects with lower soleus reflex excitability walked longer during training, but there was no change in the level or amount of muscle activity with training.  There was no change in cortical activity patterns.  Exercise conditioning effects were small or nonexistent.  However, all participants reported an average reduction in pain severity over the study period ranging between 1.3 and 1.7 on a 0-to-6 numeric rating scale.  The authors concluded that OBA training improved mobility in the OBA device without significant changes in exercise conditioning or in neuromuscular or cortical activity.  However, pain severity was reduced and no severe adverse events were encountered during training.  OBA therefore opens the possibility to reduce the common consequences of chronic, complete SCI such as reduced functional mobility and neuropathic pain.  

1. a global change after the walking session,
2. high scores on the positive and
3. low scores on the negative sensations, thus indicating a good acceptability of the robot-assisted walking. 

In contrast to other exoskeletons, HAL (hybrid assistive limb) exoskeleton (Cyberdyne Inc., Japan) offers the possibility of monitoring muscle contractions via surface EMG-electrodes at the extensor-flexor muscle region of the lower extremities (Sczensy-Kaiser et a., 2015).  This allows for voluntary machine-supported motion using minimal signals recorded from hip and knee flexors and extensors. 

Nilsson et al (2014) investigated the safety and feasibility of the exoskeleton Hybrid Assistive Limb (HAL) for intensive gait training as part of a regular inpatient rehabilitation program for hemiparetic patients with severely impaired gait early after stroke.  Eligible were patients until 7 weeks after hemiparetic stroke.  Training with HAL was performed 5 days per week by the autonomous and/or the voluntary control mode offered by the system.  The study protocol covered safety and feasibility issues and aspects on motor function, gait performance according to the 10 Meter Walking Test (10MWT) and Functional Ambulation Categories (FAC), and activity performance. Eight patients completed the study.  Median time from stroke to inclusion was 35 days (range of 6 to 46).  Training started by use of the autonomous HAL mode in all and later switched to the voluntary mode in all but one and required one or two physiotherapists.  Number of training sessions ranged from 6 to 31 (median 17) and walking time per session was around 25 minutes.  The training was well tolerated and no serious adverse events occurred.  All patients improved their walking ability during the training period, as reflected by the 10MWT (from 111.5 to 40 seconds in median) and the FAC (from 0 to 1.5 score in median).

Sczesny-Kaiser et al (2015) sought to assess whether robotic-assisted bodyweight supported treadmill training (BWSTT) with hybrid assistive limb (HAL) exoskeleton affects cortical excitability in the primary somatosensory cortex (S1) in SCI patients, as measured by paired-pulse somatosensory evoked potentials (ppSEP) stimulated above the level of injury.  Eleven SCI patients took part in HAL assisted BWSTT for 3 months.  Pulse paired stimulation techniques of somatosensory evoked potentials (PpSEP) were conducted before and after this training period, where the amplitude ratios (SEP amplitude following double pulses - SEP amplitude following single pulses) were assessed and compared to eleven healthy control subjects.  To assess improvement in walking function, the investigators used the 10-m walk test, timed-up-and-go test, the 6-min walk test, and the lower extremity motor score.  PpSEPs were significantly increased in SCI patients as compared to controls at baseline.  Following training, ppSEPs were increased from baseline and no longer significantly differed from controls.  Walking parameters also showed significant improvements, yet there was no significant correlation between ppSEP measures and walking parameters.  The investigators concluded that the findings suggest that robotic-assisted BWSTT with HAL in SCI patients is capable of inducing cortical plasticity following highly repetitive, active locomotive use of paretic legs.  While there was no significant correlation of excitability with walking parameters, brain areas other than S1 might reflect improvement of walking functions.  The investigators posited that EEG and neuroimaging studies may provide further information about supraspinal plastic processes and foci in SCI rehabilitation. 

In a pilot study, Aach et al (2014) examined if locomotor training with the exoskeleton hybrid assistive limb (HAL) exoskeleton is safe and can increase functional mobility in chronic paraplegic patients after SCI.  This trial was a single-case experimental A-B (pre-post) design study by repeated assessments of the same patients. The subjects performed 90 days (5 times per week) of HAL exoskeleton body weight supported treadmill training with variable gait speed and body weight support.  A total of 8 patients with chronic SCI classified by the American Spinal Injury Association (ASIA) Impairment Scale (AIS) consisting of ASIA A (zones of partial preservation [ZPP] L3 to S1), n = 4; ASIA B (with motor ZPP L3 to S1), n = 1; and ASIA C/D, n = 3, who received full rehabilitation in the acute and sub-acute phases of SCI.  Functional measures included treadmill-associated walking distance, speed, and time, with additional analysis of functional improvements using the 10-m walk test (10MWT), timed-up and go test (TUG test), 6-minute walk test (6MWT), and the walking index for SCI II (WISCI II) score.  Secondary physiologic measures including the AIS with the lower extremity motor score (LEMS), the spinal spasticity (Ashworth scale), and the lower extremity circumferences.  Subjects performed standardized functional testing before and after the 90 days of intervention.  Highly significant improvements of HAL-associated walking time, distance, and speed were noticed.  Furthermore, significant improvements have been especially shown in the functional abilities without the exoskeleton for over-ground walking obtained in the 6MWT, TUG test, and the 10MWT, including an increase in the WISCI II score of 3 patients.  Muscle strength (LEMS) increased in all patients accompanied by a gain of the lower limb circumferences.  A conversion in the AIS was ascertained in 1 patient (ASIA B to ASIA C); 1 patient reported a decrease of spinal spasticity.  The authors concluded that hybrid assistive limb exoskeleton training resulted in improved over-ground walking and led to the assumption of a beneficial effect on ambulatory mobility.  However, they stated that evaluation in larger clinical trials is needed.

Chihara et al (2016) investigated factors predicting the effects of HAL in 15 patients at our institution with central nervous system injury, primarily due to stroke, who underwent training using HAL during the acute phase.  Patients were classified as either “with HAL suitability” or “without HAL suitability” based on scores from 10-m walking speed, gait, satisfaction, and pain.  In both groups, Brunnstrom stage before HAL intervention, Fugl-Meyer assessment (FMA), stroke impairment assessment set (SIAS), and functional independence measure (FIM) were evaluated.  Although motor function items did not differ significantly, FIM cognitive function items (p = 0.036), visuospatial perception items on SIAS (p = 0.0277), and pain items on SIAS (p = 0.0122) differed significantly between groups.  The authors stated that these results indicated that training using HAL does not involve pain in patients with central nervous system injury during the acute phase, and exhibits positive effects in patients without pain and with high communication ability and visuospatial perception function.

Wall et al (2015) reviewed the literature on clinical applications of the Hybrid Assistive Limb (HAL) system for gait training.  A systematic literature search was conducted using Web of Science, PubMed, CINAHL and clinicaltrials.gov and additional search was made using reference lists in identified reports. Abstracts were screened, relevant articles were reviewed and subject to quality assessment.  Out of 37 studies, 7 studies fulfilled inclusion criteria.  Six studies were single group studies and 1 was an explorative randomized controlled trial.  In total, these studies involved 140 participants of whom 118 completed the interventions and 107 used HAL for gait training.  Five studies concerned gait training after stroke, 1 after spinal cord injury (SCI) and 1 study after stroke, SCI or other diseases affecting walking ability.  Minor and transient side effects occurred but no serious adverse events were reported in the studies.  Beneficial effects on gait function variables and independence in walking were observed.  The accumulated findings demonstrate that the HAL system is feasible when used for gait training of patients with lower extremity paresis in a professional setting.  Beneficial effects on gait function and independence in walking were observed but data do not allow conclusions.  The investigators stated that further controlled studies are recommended.

Swank, et al. (2020) sought to compare temporospatial, kinematic, and muscle activity gait characteristics before and after a single EKSO session and examine kinematic symmetry between involved and uninvolved limbs. Participants post-stroke walked under two conditions: pre-EKSO, and immediately post-EKSO. A 10-camera motion capture system synchronized with 6 force plates was used to obtain temporospatial and kinematic gait characteristics from 5 walking trials of 9 meters at a self-selected speed. Surface EMG activity was obtained from bilateral gluteus medius, rectus femoris, medial hamstrings, tibialis anterior, and soleus muscles. Wilcoxon Signed Rank tests were used to analyze differences pre- and post-EKSO. Single EKSO session consisted of 22.3±6.8 minutes total time (walk time=7.2±1.5 minutes) with 250±40  steps. Six ambulatory (Functional Ambulation Category, range=4-5) adults (3 female; 44.7±14.6 years) with chronic stroke (4.5±1.9 years post-stroke) participated. No significant differences were observed for temporospatial gait characteristics. Muscle activity was significantly less post-EKSO in the involved leg rectus femoris during swing phase (p=0.028). Ankle dorsiflexion range of motion on the involved leg post-EKSO was significantly less during stance phase (p=0.046). Differences between involved and uninvolved joint range of motion symmetry were found pre-EKSO but not post-EKSO in swing phase hip flexion and stance phase knee flexion and knee extension. The investigators concluded that EKSO training appears capable of altering gait in people with chronic stroke and a viable intervention to reduce gait dysfunction post-stroke.

Rojek, et al. (2020) sought to evaluate the effects of EKSO GT exoskeleton-assisted gait training on balance, load distribution, and functional status of patients after ischemic stroke. Study outcomes were based on 44 patients aged 55-85 years after ischemic stroke who were previously randomly assigned into two groups: experimental (with EKSO GT rehabilitation) and control (with classical rehabilitation). At baseline and after 4 weeks of treatment, the patients were evaluated on balance, load distribution, and functional status using, respectively a stabilometric platform, the Barthel Index, and the Rivermead Mobility Index. In the experimental group, balance improved regarding the variables describing sway area as ellipse major and minor axes. In the control group, improvement was noted in sway velocity. After the therapy, total load distribution on feet in both groups showed a small and insignificant tendency toward reduction in the amount of uninvolved limb loading. In the control group, significant load transfer from the backfoot to the forefoot was noted. Both forms of rehabilitation caused significant changes in functional status. The investigators concluded that both training with the use of the EKSO GT exoskeleton and classical physiotherapy lead to functional improvement of patients after ischemic stroke. However, in the experimental group, improvement was observed in a larger number of categories, which may suggest potentially greater impact of treatment with the exoskeleton on functional status. Also, both forms of rehabilitation caused significant changes in balance, but the investigators had noted some trends indicating that treatment with exoskeleton may be more beneficial for some patients. The load transfer from the backfoot to the forefoot observed in the control group was an unfavorable phenomenon. The investigators suggested that the Ekso GT exoskeleton may be a promising tool in the rehabilitation of patients after stroke.

Swank, et al. (2019) examined whether wearing a robotic exoskeleton affects temporospatial parameters, kinematics, and muscle activity during gait. The study was completed by 15 healthy adults (mean age 26.2 [SD 8.3] years; 6 males, 9 females). Each participant performed walking under 2 conditions: with and without wearing a robotic exoskeleton (EKSO). A 10-camera motion analysis system synchronized with 6 force plates and a surface electromyography (EMG) system captured temporospatial and kinematic gait parameters and lower extremity muscle activity. For each condition, data for 5 walking trials were collected and included for analysis. Differences were observed between the 2 conditions in temporospatial gait parameters of speed, stride length, and double-limb support time. When wearing EKSO, hip and ankle range of motion (ROM) were reduced and knee ROM increased during the stance phase. However, during the swing phase, knee and ankle ROM were reduced when wearing the exoskeleton bionic suit. When wearing EKSO, EMG activity decreased bilaterally in the stance phase for all muscle groups of the lower extremities and in the swing phase for the distal muscle groups (tibialis anterior and soleus) as well as the left medial hamstrings. The investigators concluded that wearing EKSO altered temporospatial gait parameters, lower extremity kinematics, and muscle activity during gait in healthy adults. EKSO appears to promote a type of gait that is disparate from normal gait in first-time users. The investigators stated that more research is needed to determine the impact on gait training with EKSO in people with gait impairments.

Swank et al. (2010) sought to determine the feasibility of integrating the Ekso Gait Training device into inpatient rehabilitation in a neurologic population. The study included a longitudinal cohort design and convenience sample including physical therapists trained to use the Ekso Bionics Ekso GT robotic exoskeleton or inpatients with stroke or SCI. Therapists completed a focus group and survey at baseline and 6 months after initial Ekso training. Patients completed a survey indicating their satisfaction with using the Ekso. Twenty-five patients used the Ekso an average of 4.5 sessions during their 38.5-day rehabilitation stay. Survey and focus group feedback revealed that therapists encountered measurement difficulties with the Ekso and limited treatment time influencing effectiveness of usage. After 6 months, therapists reported an improvement in feasibility. Patients tolerated Ekso sessions well, without any complications or adverse incidents, and reported improved mobility post session. The investigators concluded that integrating Ekso gait training into clinical practice was not seamless but appears feasible. Barriers were addressed within the rehabilitation team and received administrative support in a process lasting several months. Patients enjoyed walking in Ekso and felt secure within the device. 

Poritz, et al. (2020) reported on the results of a robotic exoskeleton user satisfaction questionnaire completed by participants utilizing two robotic exoskeletons. Seven individuals with physical disabilities engaged in two exoskeleton-assisted training phases with the REX and the Ekso 1.1 (Ekso), after which they completed a user satisfaction questionnaire. The questionnaire consisted of structured items with a Likert scale, which were averaged and compared, as well as free response questions, which were interpreted thematically. Participants reported some differences in user satisfaction between the two exoskeletons. They indicated higher satisfaction with transferring in and out of the REX and with its appearance and higher satisfaction with the transportability of the Ekso. Expectations for exoskeleton use were relatively similar for the two devices, with some exceptions. Whereas participants indicated that many changes should be made to both exoskeletons, they reported that some were more necessary for the REX and others were more necessary for the Ekso. Participants reported that they would be somewhat likely to use both exoskeletons at home and in the community if they were available. 

Gorman, et al. (2019) reported on a randomized dual center controlled clinical trial to determine and compare the cardiorespiratory impact of 3 months of aquatic and robotic therapy for individuals with chronic motor incomplete spinal cord injury (CMISCI). Thirty-one individuals at two rehabilitation specialty hospitals with CMISCI with neurological level between C2-T12 at least 1 year post injury were randomized to either aquatic or robotic treadmill therapy for 36 sessions. Customized sessions lasted 40-45 min at 65-75% heart rate reserve intensity with peak oxygen consumption (peak VO2) measured during arm ergometry at baseline and post intervention. Additional peak robotic treadmill VO2 assessments were obtained before and after training for participants randomized to robotic intervention. Peak VO2 measured with arm ergometry was not significantly different with either aquatic intervention (8.1%, p = 0.14, n = 15) or robotic intervention (-0.7%, p = 0.31, n = 17). Peak VO2 measured with robotic treadmill ergometry demonstrated a statistical improvement (14.7%, p = 0.03, n = 17, two-tailed t-test) across the robotic intervention. Comparison between the two interventions demonstrated a trend favoring aquatic therapy for improving arm ergometry peak VO2 (ANOVA, p = 0.063).  The authors concluded that neither 3-month exercise interventions statistically improved arm cycle ergometry peak VO2, the study's cardiorespiratory surrogate marker, although percent improvement was greater in the aquatic exercise condition. Robotic ergometry peak VO2 did improve for the robotic intervention, confirming previous work. These results suggest that either intervention may hold utility in improving cardiorespiratory fitness in CMISCI, but peak VO2 measurement technique appears critical in detecting effects.

Alamro, et al. (2018) conducted a study to characterize and compare the activation of the trunk muscles during walking with two robotic gait training devices (Ekso and Lokomat) in people with high thoracic motor-complete SCI. Participants with chronic motor-complete paraplegia performed 3 speed-matched walking conditions: Lokomat-assisted walking, Ekso-assisted walking overground, and Ekso-assisted walking on a treadmill. Surface electromyography (EMG) signals were recorded bilaterally from the rectus abdominis (RA), external oblique (EO), and erector spinae (ES) muscles. Greater recruitment of trunk muscle EMG was elicited with Ekso-assisted walking compared to the Lokomat. Similar levels of trunk EMG activation were observed between Ekso overground and Ekso on the treadmill, indicating that differences between Ekso and Lokomat could not be attributed to the use of a hand-held gait aid. The level of trunk EMG activation during Lokomat walking was not different than that recorded during quiescent supine lying.

Baunsgaard, et al. (2018) conducted a prospective, observational multicenter study to explore changes in pain, spasticity, range of motion, activities of daily living, bowel and lower urinary tract function and quality of life of individuals with spinal cord injury following robotic exoskeleton gait training. Subjects underwent three training sessions per week for 8 weeks using an Ekso GT robotic exoskeleton. Included were individuals with recent (<1 year) or chronic (>1 year) injury, paraplegia and tetraplegia, complete and incomplete injury, men and women. Fifty-two participants completed the training protocol. Pain was reported by 52% of participants during the week prior to training and 17% during training, but no change occurred longitudinally. Spasticity decreased after a training session compared with before the training session (p <0.001), but not longitudinally. Chronically injured participants increased Spinal Cord Independence Measure (SCIM III) from 73 to 74 (p = 0.008) and improved life satisfaction (p = 0.036) over 8 weeks of training. Recently injured participants increased SCIM III from 62 to 70 (p < 0.001), but no significant change occurred in life satisfaction. Range of motion, bowel and lower urinary function did not change over time.

Gorgey, et al. (2017) studied whether the use of a powered exoskeleton can improve parameters of physical activity as determined by walking time, stand up time, and number of steps in persons with spinal cord injury (SCI). Three men with complete (1 C5 AIS A and 2 T4 AIS A) and one man with incomplete (C5 AIS D) SCI participated in a clinical rehabilitation program. In the training program, the participants walked once weekly using a powered exoskeleton (Ekso) for approximately 1 hour over the course of 10 to 15 weeks. Walking time, stand up time, ratio of walking to stand up time, and number of steps were determined. Oxygen uptake (L/min), energy expenditure, and body composition were measured in one participant after training. Over the course of 10 to 15 weeks, the maximum walking time increased from 12 to 57 minutes and the number of steps increased from 59 to 2,284 steps. At the end of the training, the 4 participants were able to exercise for 26 to 59 minutes. For one participant, oxygen uptake increased from 0.27 L/min during rest to 0.55 L/min during walking. Maximum walking speed was 0.24 m/s, and delta energy expenditure increased by 1.4 kcal/min during walking. Body composition showed a modest decrease in absolute fat mass in one participant. 

Bach Baunsgaard (2018) et al. conducted a prospective pre-post study at nine European rehabilitation centers to assess the safety, feasibility, training characteristics and changes in gait function for persons with spinal cord injury (SCI) using the robotic exoskeletons from Ekso Bionics. Subjects underwent robotic exoskeleton gait training, three times weekly over 8 weeks. Time upright, time walking and steps in the device (training characteristics) were recorded longitudinally. Gait and neurological function were measured by 10 Meter Walk Test (10 MWT), Timed Up and Go (TUG), Berg Balance Scale (BBS), Walking Index for Spinal Cord Injury (WISCI) II and Lower Extremity Motor Score (LEMS). Fifty-two participants completed the training protocol. Subjects median age was 35.8 years (IQR 27.5-52.5), and included 36 men and 16 women, with neurological level of injury at C1-L2 and severity AIS A-D (American Spinal Injury Association Impairment Scale). The time since injury (TSI)  was less than 1 year in 25 subjects, and greater than 1 year in 27 subjects. No serious adverse events occurred. Three participants dropped out following ankle swelling (overuse injury). Four participants sustained a Category II pressure ulcer at contact points with the device but completed the study and skin normalized. Training characteristics increased significantly for all subgroups. The number ofmparticipants with TSI < 1 year and gait function increased from 20 to 56% (P = 0.004) and 10MWT, TUG, BBS and LEMS results improved (P < 0.05). The number of participants with TSI > 1 year and gait function, increased from 41 to 44% and TUG and BBS results improved (P < 0.05).

The Indego exoskeleton (Parker Hannifin Corporation, Macedonia, OH) incorporates 4 motors for powered movement of bilateral hip and knee joints in the sagittal plane, in addition to built-in ankle-foot-orthoses (AFOs) at both ankle joints to provide ankle stability and transfer the weight of the exoskeleton to the ground.

Hartigan et al (2015) conducted a study to evaluate mobility outcomes for individuals with SCI after 5 gait-training sessions with the Indego powered exoskeleton, with a primary goal of characterizing the ease of learning and usability of the system.  Sixteen subjects with SCI were enrolled in a pilot clinical trial at Shepherd Center, Atlanta, Georgia, with injury levels ranging from C5 complete to L1 incomplete.  An investigational Indego exoskeleton research kit was evaluated for ease of use and efficacy in providing legged mobility.  Outcome measures of the study included the 10-meter walk test (10MWT) and the 6-minute walk test (6MWT) as well as measures of independence including donning and doffing times and the ability to walk on various surfaces.  At the end of 5 sessions (1.5 hours per session), average walking speed was 0.22 m/s for persons with C5-6 motor complete tetraplegia, 0.26 m/s for T1-8 motor complete paraplegia, and 0.45 m/s for T9-L1 paraplegia.  Distances covered in 6 minutes averaged 64 meters for those with C5-6, 74 meters for T1-8, and 121 meters for T9-L1.  Additionally, all participants were able to walk on both indoor and outdoor surfaces. 

Evans et al (2015) conducted a pilot study to evaluate the acute cardiorespiratory and metabolic responses associated with Indego exoskeleton-assisted walking overground and to determine the degree to which these responses change at differing walking speeds.  Five subjects (4 male, 1 female) with chronic SCI (AIS A) volunteered for the study.  Expired gases were collected during maximal graded exercise testing and two, 6-minute bouts of exoskeleton-assisted walking overground.  Outcome measures included peak oxygen consumption (VO2peak), average oxygen consumption (VO2avg), peak heart rate (HRpeak), walking economy, metabolic equivalent of tasks for SCI (METssci), walk speed, and walk distance.  Significant differences were observed between walk-1 and walk-2 for walk speed, total walk distance, VO2avg, and METssci.  Exoskeleton-assisted walking resulted in % VO2peak range of 51.5 % to 63.2 %.  The metabolic cost of exoskeleton-assisted walking ranged from 3.5 to 4.3 METssci.

Tefertiller, et al. (2018) assessed the safety and mobility outcomes utilizing the Indego powered exoskeleton in indoor and outdoor walking conditions with individuals previously diagnosed with a spinal cord injury (SCI). The investigators conducted a multicenter prospective observational cohort study in outpatient clinics associated with 5 rehabilitation hospitals. A convenience sample of nonambulatory individuals with SCI (N = 32) completed an 8-week training protocol consisting of walking training 3 times per week utilizing the Indego powered exoskeleton in indoor and outdoor conditions. Participants were also trained in donning/doffing the exoskeleton during each session. Safety measures such as adverse events (AEs) were monitored and reported. Time and independence with donning/doffing the exoskeleton as well as walking outcomes to include the 10-meter walk test (10MWT), 6-minute walk test (6MWT), Timed Up & Go test (TUG), and 600-meter walk test were evaluated from midpoint to final evaluations. All 32 participants completed the training protocol with limited device-related AEs, which resulted in no interruption in training. The investigators reported that the majority of participants in this trial were able to don and doff the Indego independently. Final walking speed ranged from 0.19 to 0.55 m/s. Final average indoor and outdoor walking speeds among all participants were 0.37 m/s (SD = 0.08, 0.09, respectively), after 8 weeks of training. Significant (p < .05) improvements were noted between midpoint and final gait speeds in both indoor and outdoor conditions. Average walking endurance also improved among participants after training. 

Takahashi and colleagues (2015) stated that in persons post-stroke, diminished ankle joint function can contribute to inadequate gait propulsion. To target paretic ankle impairments, these researchers developed a neuromechanics-based powered ankle exoskeleton.  Specifically, this exoskeleton supplies plantar-flexion assistance that is proportional to the user's paretic soleus electromyography (EMG) amplitude only during a phase of gait when the stance limb is subjected to an anteriorly directed ground reaction force (GRF).  In a feasibility study, these investigators examined the short-term effects of the powered ankle exoskeleton on the mechanics and energetics of gait. Invesigators fabricated a lightweight ankle exoskeleton for each individual’s paretic limb.   A total of 5 subjects with stroke walked with a powered ankle exoskeleton on the paretic limb for 3 sessions (5 mins each session).  They analyzed the peak paretic ankle plantar-flexion moment, paretic ankle positive work, symmetry of GRF propulsion impulse, and net metabolic power.  The exoskeleton increased the paretic plantar-flexion moment by 16 % during the powered walking trials relative to unassisted walking condition (p < 0.05).  Despite this enhanced paretic ankle moment, there was no significant increase in paretic ankle positive work, or changes in any other mechanical variables with the powered assistance.  The exoskeleton assistance appeared to reduce the net metabolic power gradually with each 5-min repetition, though no statistical significance was found.  In 3 of the subjects, the paretic soleus activation during the propulsion phase of stance was reduced during the powered assistance compared to unassisted walking (35 % reduction in the integrated EMG amplitude during the 3rd powered session).  The authors concluded that the findings of this feasibility study demonstrated that the exoskeleton can enhance paretic ankle moment.  Moreover, they stated that future studies with greater sample size and prolonged sessions are needed to evaluate the effects of the powered ankle exoskeleton on overall gait outcomes in persons post-stroke.

Wilcox et al (2016) examined peak interaction forces and electromyography (EMG) analysis to examine whether such interaction forces are due to the muscular activity of the participant or the movement of the REX Personal (Rex Bionics, New Zealand) exoskeleton itself.  Interestingly, the authors found that peak forces preceded peak EMG activity.  This study did not find a significant correlation between EMG activity and force data, which would indicate that the interaction forces can largely be attributed to the movement of the exoskeleton itself.  However, we also report significantly higher correlation coefficients in muscle/force pairs located at the anterior aspect of the right leg.  In their previous research, the authors have shown peak interaction forces at the same locations, which suggests that muscular activity of the participant makes a more significant contribution to the interaction forces at these locations. 

Birch, et al. (2017) reported interim results of the RAPPER II study investigating the feasibility, safety and acceptability of using the REX self-stabilizing robotic exoskeleton in people with spinal cord injury (SCI) who are obligatory wheelchair users. Feasibility was assessed by the completion of transfer into the REX device, competency in achieving autonomous control and completion of upper body exercise in an upright position in the REX device. Safety was measured by the occurrence of serious adverse events. Device acceptability is assessed with a user questionnaire. RAPPER II is a prospective, multi-center, open label, non-randomized, non-comparative cohort study in people with SCI recruited from neurological rehabilitation centres in the United Kingdom, Australia and New Zealand. This report was the planned interim report of the first 20 participants. Each completed a transfer into the REX, were trained to achieve machine control and completed Timed Up and Go (TUG) tests as well as upper body exercises in standing in a single first time session. The time to achieve each task as well as the amount of assistance required was recorded. After finishing the trial tasks a User Experience questionnaire, exploring device acceptability, was completed. All participants could transfer into the REX. The mean transfer time was 439 s. Nineteen completed the exercise regime. Eighteen could achieve autonomous control of the REX, 17 of whom needed either no assistance or the help of just one therapist. Eighteen participants completed at least one TUG test in a mean time of 313 s, 15 with the assistance of just one therapist. The questionnaire demonstrated high levels of acceptability amongst users. There were no serious adverse events.

Arazpour et al (2013) analyzed the energy expenditure during walking with mechanical orthoses (hip knee ankle foot orthosis (HKAFO) and the isocentric reciprocating gait orthosis (IRGO)) compared with a new powered gait orthosis (PGO) in patients with SCI. Five patients with SCI who were experienced users of HKAFOs participated in this study. Subjects were also fitted with an IRGO and PGO and underwent a specific gait training program. Patients walked along a flat walkway using the three types of orthosis at their self-selected walking speed. A stop watch and a polar heart rate monitor were used to measure the speed of walking and heart rate. The authors reported that walking speed, the distance walked and the physiological cost index (PCI) all improved with both the new PGO and the IRGO as compared with the HKAFO.

Gholizadeh et al (2014a) noted that a number of prosthetic suspension systems are available for trans-tibial amputees.  Consideration of an appropriate suspension system can ensure that amputee's functional needs are satisfied.  The higher the insight to suspension systems, the easier would be the selection for prosthetists.  These investigators attempted to find scientific evidence pertaining to various trans-tibial suspension systems to provide selection criteria for clinicians.  Databases of PubMed, Web of Science, and ScienceDirect were explored to find related articles.  Search terms were as follows: "Transtibial prosthesis (32), prosthetic suspension (48), lower limb prosthesis (54), below-knee prosthesis (58), prosthetic liner (20), transtibial (193), and prosthetic socket (111)".  Two reviewers separately examined the papers.  Study design (case series of 5 or more subjects, retrospective or prospective), research instrument, sampling method, outcome measures and protocols were reviewed.  Based on the selection criteria, 22 articles (15 prospective studies, and 7 surveys) remained.  Sweat control was found to be a major concern with the available suspension liners.  Donning and doffing procedures for soft liners were also problematic for some users, particularly those with upper limb weakness.  Moreover, the total surface bearing (TSB) socket with pin/lock system is favored by the majority of amputees.  The authors concluded that no clinical evidence was available to suggest what kind of suspension system could have an influential effect as a "standard" system for all trans-tibial amputees.  However, among various suspension systems for trans-tibial amputees, the Iceross system was favored by the majority of users in terms of function and comfort.

Gholizadeh et al (2014b) examined the scientific evidence pertaining to various trans-femoral suspension systems to provide selection criteria for clinicians.  Databases of PubMed, Web of Science, and ScienceDirect were explored.  The following key words, as well as their combinations and synonyms, were used for the search: transfemoral prosthesis, prosthetic suspension, lower limb prosthesis, above-knee prosthesis, prosthetic liner, transfemoral, and prosthetic socket.  The study design, research instrument, sampling method, outcome measures, and protocols of articles were reviewed.  On the basis of the selection criteria, a total of 16 articles (11 prospective studies and 5 surveys) were reviewedd.  The main causes of reluctance to prosthesis, aside from energy expenditure, were socket-related problems such as discomfort, perspiration, and skin problems.  Osseo-integration was a suspension option, yet it is rarely applied because of several drawbacks, such as extended rehabilitation process, risk for fracture, and infection along with excessive cost.  The authors concluded that no clinical evidence was found as a "standard" system of suspension and socket design for all trans-femoral amputees.  However, among various suspension systems for trans-femoral amputees, the soft insert or double socket was favored by most users in terms of function and comfort.

According to the Ottobock website, the C-Leg Protector 4X160 represents the modern solution for C-Leg and C-Leg compact wearers.  The C-Leg Protector covers and protects the joints of the C-Leg Product Line, including the tube adapter, and provides a cosmetic contour in the calf area.  The manufacturer states that the result is an attractive appearance without any functional restrictions.  The website states that the C-Leg Protector can be used on right or left sides and is quick and easy to adjust.  According to the manufacturer, during everyday use, the patient  can put it on, take it off, and clean it easily if needed. 

The Ossur Symbiotic Leg (Ossur Americas, Foothill ranch, CA), a microprocessor knee/foot unit, combines the capabilities of the bionic products, RHEO KNEE and PROPRIO FOOT, into a single integrated unit offering  functionality for TF (above knee) amputees.  The prosthesis was designed to enable users to experience confident mobility on all terrains without gait deviations or compensations.  This new product, which is the first of its kind in the market, has been in user testing for over a year and will be available on a limited basis in late 2011. 

Alimusaj et al (2009) stated that conventional prosthetic feet cannot adapt to specific conditions such as walking on stairs or ramps.  Amputees are therefore forced to compensate their prosthetic deficits by modifying the kinematics and kinetics of their lower limbs.  The Proprio-Foot (Ossur) intends to reduce these compensation mechanisms by automatically increasing dorsiflexion during stair ambulation thanks to an adaptive microprocessor-controlled ankle.  These investigators analyzed the biomechanical effects of the dorsiflexion adaptation in trans-tibial (TT) amputees during stair ambulation.  A total of 16 TT amputees and 16 healthy controls underwent conventional 3D gait analysis.  Kinematics and kinetics of the lower limbs were compared during stair ascent and descent performed by patients with the prosthetic foot set to a neutral ankle angle and with an adapted dorsiflexion ankle angle of 4 degrees.  Norm distance as well as minimum and maximal values of sagittal kinematics and kinetics were calculated for comparisons between patients and control subjects.  For both stair ascent and descent, an improvement of the knee kinematics and kinetics could particularly be noticed on the involved side with an increase of the knee flexion and an increase of the knee moment during stance.  The authors concluded that d despite its additional weight compared to a conventional prosthetic ankle, the Proprio-Foot should be beneficial to active TT amputees whose knee musculature strength does not constitute a handicap.

Wolf et al (2009) stated that the technological advances have been made in developing highly functional prostheses are promising for very active patients but it is unknown whether they cause an increase in biomechanical load along with possibly negative consequences for pressure conditions in the socket.  Therefore, this study monitored the socket pressure at specific locations of the stump when using a microprocessor-controlled adaptive prosthetic ankle under different walking conditions.  A total of 12 unilateral TT amputees (TTAs) between 43 and 59 years of age were provided with the Proprio-Foot (Ossur) and underwent an instrumented 3D gait analysis in level, stair, and incline walking, including synchronous data capturing of socket pressure.  Peak pressures and pressure time integrals (PTI) at 3 different locations were compared for 5 walking conditions with and without using the device's ankle adaptation mode.  Highest peak pressures of 2.4 k Pa/kg were found for incline ascent at the calf muscle as compared to 2.1 k Pa/kg in level walking with large inter-individual variance.  In stair ascent a strong correlation was found between maximum knee moment and socket pressure.  The most significant pressure changes relative to level walking were seen in ramp descent anteriorly towards the stump end, with PTI values being almost twice as high as those in level walking.  Adapting the angle of the prosthesis on stairs and ramps modified the pressure data such that they were closer to those in level walking.  The authors concluded that pressure at the stump depended on the knee moments involved in each walking condition.  Adapting the prosthetic ankle angle is a valuable means of modifying joint kinetics and thereby the pressure distribution at the stump.  However, large inter-individual differences in local pressures underline the importance of individual socket fitting.

Fradet et al (2010) noted that the fixed neutral position of conventional prosthetic feet causes difficulties for TTAs when walking on ramps.  New microprocessor-controlled prosthetic ankles such as the Proprio-Foot (Ossur) aim to reduce these difficulties by modifying the prosthetic ankle angle according to the gait condition.  These researchers evaluated the biomechanical effects of adaptation of the prosthetic ankle on ramp ambulation in TTAs.  A total of 16 TTAs and 16 controls underwent a conventional 3D gait analysis while walking up and down a ramp.  Trans-tibial amputees walked with the prosthetic foot set to a neutral mode angle and set to the adapted mode.  Norm distance, sagittal kinematics and kinetics were calculated for comparisons between TTAs and controls.  During ramp ascent, the dorsiflexion brought about by the adapted prosthetic ankle reduced the increased knee extension noted on the TTAs' involved side and the increased plantar-flexion on their sound side.  During ramp descent, the plantar-flexion of the adapted mode increased the adaptation mechanisms observed in TTAs.  The authors concluded that these findings suggested that the adapted mode leads to more physiologic kinematics and kinetics in the lower limbs in TTAs during ramp ascent but not during ramp descent.  However, in the adapted mode, patients reported feeling safer during ramp descent, thus indicating that there might be other safety related measures such as toe-clearance or co-efficient of friction influencing this perception.  (This study appeared to have the same subjects (n = 16) and controls (n = 16) as the 2009 study by Alimusaj et al; and Fradet was the 2nd author in that study).

In an unpublished study, Ludviksdottir (2012) evaluated the effect on mobility and safety for lower limb amputees (LLA; n = 8) when changing from a carbon fiber prosthetic foot to a bionic foot.  Results suggested that user mobility improves when using the bionic foot and subjects experienced fewer falls and stumbles.  The authors concluded that despite the limitation of the study, which is small sample size (n = 8) and mixing above knee and below knee amputees, the results indicated that improvements in perceived mobility and reduced risk of falling while using the bionic foot -- may relate to the intelligent functions offered by the bionic foot; in particular, the toe-lift in swing and terrain adaptation, functions which are not offered by mechanical prosthetic feet.  They stated that to confirm these preliminary findings, a larger study is needed.

Rosenblatt et al (2014) stated that people with amputation are at increased risk of falling compared with age-matched, non-disabled individuals.  This may partly reflect amputation-related changes to minimum toe clearance (MTC) that could increase the incidence of trips and fall risk.  This study determined the contribution of a dorsiflexing prosthesis to MTC.  These researchers hypothesized that regardless of speed or incline the active dorsiflexion qualities of the ProprioFoot would significantly increase MTC and decrease the likelihood of tripping.  A total of 8 TTAs walked on a treadmill with their current foot at 2 grades and 3 velocities, then repeated the protocol after 4 weeks of accommodation with the ProprioFoot.  A mixed-model, repeated-measures analysis of variance was used to compare MTC.  Curves representing the likelihood of tripping were derived from the MTC distributions and a multiple regression was used to determine the relative contributions of hip, knee, and ankle angles to MTC.  Regardless of condition, MTC was approximately 70 % larger with the ProprioFoot (p < 0.001) and the likelihood of tripping was reduced.  Regression analysis revealed that MTC with the ProprioFoot was sensitive to all 3 angles, with sensitivity of hip and ankle being greater.  The authors concluded that the ProprioFoot may increase user safety by decreasing the likelihood of tripping and thus the pursuant likelihood of a fall.

Rosenblatt et al (2017) noted that individuals with TTA are at increased risk of falling.  The absence of an ankle joint and the associated musculature in these individuals can reduce clearance between the prosthetic foot and ground during the swing phase of gait, which may increase the risk of stumbling and in turn falling.  In a prospective, cohort study, these researchers attempted to associate minimum toe clearance (MTC; defined as a local minimum of the vertical displacement of the toe from toe-off to heel-strike relative to its position during mid-stance) during gait in the laboratory with community-based, trip-related stumbles by individuals with TTA using conventional feet.  Participants completed electronic surveys to prospectively report stumbles and falls for 1 year thereafter.  A volunteer sample of 8 unilateral, trans-tibial amputees who were K3- or K4-level ambulators and current patients at a local prosthetic clinic participated in this study.  All participants completed the entire 1-year follow-up study.  Prosthetic-side MTC while walking on a level treadmill at self-selected velocity (SSV) and self-reported trip-related stumbles in the community were recorded.  Prosthetic-side MTC was more than 50 % lower for participants who reported 1 or more trip-related stumbles on that side compared with participants who reported zero trip-related stumbles on the prosthetic side (MTC = 12.3 ± 0.8 mm versus 25.6 ± 5.4 mm, respectively; p = 0.036).  The authors concluded that this was the 1st study relating laboratory-based measures to prospective stumbles by prosthesis users.  The results suggested that prosthesis users with low MTC may be at increased risk of experiencing a trip-related stumble in the community.  They stated that these preliminary findings justified the need for a larger study to relate MTC and the causes of community-based stumbles and falls by individuals with TTA.

1. given the small sample size (n = 8), the study may be under-powered to detect a relationship between prosthetic-side MTC and any-cause stumbles, although, as discussed, these results were expected and logical.  To minimize the influence of small sample size, these researchers included data from 2 participants (P7 and P14) who did not walk on a treadmill at 0 % grade and at SSV.  However, inclusion was justified, and given the large effect size, even excluding these subjects would not result in p > 0.05,
2. based on the definition, self-report of stumbles may be more subjective than that of falls, which may explain the high inter-subject variability in this measure (e.g., the high number of stumbles reported by participant P7 may reflect individual hyper-vigilance with regard to balance loss.  This subject may have reported events that other participants ignored or deemed unimportant to report.  Increasing sample size would reduce this variability, and
3. the results of this study were limited to subjects who were 30 years of age and older and may not generalize to younger prosthesis users.

Powered Lower Limb Prosthesis

Carey et al (2015) stated that the choice of a myoelectric or body-powered upper-limb prosthesis can be determined using factors including control, function, feedback, cosmesis, and rejection. Although body-powered and myoelectric control strategies offer unique functions, many prosthesis users must choose one.  These investigators performed a systematic review to determine differences between myoelectric and body-powered prostheses to inform evidence-based clinical practice regarding prescription of these devices and training of users.  A search of 9 databases identified 462 unique publications.  A total of 31 of them were included and 11 empirical evidence statements were developed.  Conflicting evidence has been found in terms of the relative functional performance of body-powered and myoelectric prostheses.  Body-powered prostheses have been shown to have advantages in durability, training time, frequency of adjustment, maintenance, and feedback; however, they could still benefit from improvements of control.  Myoelectric prostheses have been shown to improve cosmesis and phantom-limb pain and are more accepted for light-intensity work.  The authors concluded that current evidence is insufficient to conclude that either system provides a significant general advantage.  Prosthetic selection should be based on a patient's individual needs and include personal preferences, prosthetic experience, and functional needs.  This work demonstrated that there is a lack of empirical evidence regarding functional differences in upper-limb prostheses.

Proprio Foot

Gailey et al (2012) examined the application of outcome measures to determine changes in function caused by standardized functional prosthetic gait training and the use of 4 different prosthetic feet in people with unilateral trans-tibial limb loss; 2  self-report measures (Prosthetic Evaluation Questionnaire-Mobility Scale [PEQ-13] and Locomotor Capabilities Index [LCI]), and 3 performance-based measures (Amputee Mobility Predictor with a prosthesis [AMPPRO], 6-minute walk test [6MWT] and step activity monitor [SAM]) were used.  A total of 10 people with unilateral trans-tibial limb loss, 5 with peripheral vascular disease (PVD) and 5 without PVD, completed testing.  Subjects were tested at baseline and after receiving training with their existing prosthesis and with the study socket and 4 prosthetic feet, i.e., SACH (solid ankle cushion heel), SAFE (stationary attachment flexible endoskeletal), Talux, and Proprio Feet, over 8 to 10 weeks.  Training was administered between testing sessions.  No differences were detected by the PEQ-13, LCI, 6MWT, or SAM following training and after fitting with test feet.  The AMPPRO demonstrated differences following training with the existing prosthesis in the PVD group and between selected feet from baseline testing (p </= 0.05).  Significant differences were found between the PVD and the non-PVD groups (p </= 0.05) in the AMPPRO and 6MWT when using the Proprio Foot.  Self-report measures were unable to detect differences between prosthetic feet.

The authors stated that drawbacks related to this study were similar to many studies that examined prosthetic components.  For example, the small sample size (n = 10) was not related to recruiting but rather to the cost and time constraints needed to train each subject, fabricate the sockets, maintain the prostheses, and buy the prosthetic feet and other prosthesis-related components.  A larger study population would certainly increase the power of this study and increase the confidence in the results.  Additionally, alternative prosthetic foot designs might demonstrate different results from those feet selected in this trial; because of the constraints previously described, this study was limited to 4 feet.  These investigators hoped that this article motivated further research to examine the use of these and other self-report and performance-based outcome measures in a larger sample of individuals who are functioning at all levels and, in particular, at the lower levels.  In addition, these researchers did not evaluate the value of the prosthetic socket and suspension system and this should be incorporated into future studies.  Lastly, using instrumented functional gait analysis, such as force distribution, stride length, and step width, could provide objective findings in determining potential differences among different prosthetic feet.

1. with a standard suction system (SSS) and the DCF;
2. with the DCF after 7 weeks of using a hypobaric suspension system (HSS) with the DCF;
3. after 1 hour of Proprio-Foot use together with the HSS; and 3 more testing sessions were carried out at 30-day intervals, i.e., after 30, 60 and 90 days of Proprio-Foot use together with the HSS; TTAs perceived mobility using the prosthesis and walking ability on stairs and ramps were assessed. 

A total of 10 TTAs completed the measurements; ECW with the Proprio-Foot obtained in the final floor-walking test was significantly lower than ECW with the DCF (p = 0.002).  No significant improvements were observed for perceived mobility or walking ability.  The authors concluded that these findings suggested that use of the Proprio-Foot can lower the ECW for TTAs in spite of its added weight compared to DCF.  Moreover, they stated that further studies are needed to investigate ECW, quality of life (QOL), perceived mobility and motor capability in older and/or less active TTAs.

This study had several drawbacks.  First, small sample size (n = 10).  Second, the authors were aware that to achieve the secondary aim, i.e., to compare the effects of the Proprio Foot on ECW with those of the DCF, the same data collection should had been carried out in TTAs using the Proprio-Foot1 in association with their usual standard suction socket.  Finally, the subjects included TTAs with high functional status who had a young mean age.  Thus, the results could not be generalized across a wider population.

Agrawal et al (2013) stated that contrary to stance-phase dorsiflexion of conventional prosthetic feet, the microprocessor-controlled Proprio Foot allows swing-phase dorsiflexion on stairs.  These researchers compared Symmetry in External Work (SEW) between a microprocessor-controlled foot and conventional prosthetic feet in 2 groups with unilateral trans-tibial amputation (TTA) (Medicare Functional Classification Levels K-Level-2 and K-Level-3) during stair ascent and descent.  A total of 10 subjects were evaluated while wearing 3 conventional prosthetic feet -- solid ankle cushion heel (SACH), stationary attachment flexible endoskeleton (SAFE), and Talux-and the Proprio Foot using a study socket and were given a 10- to 14-day accommodation period with each foot.  Ground reaction forces  (GRFs) were collected using F-scan sensors during stair ascent and descent.  The SEW between the intact and amputated limbs was calculated for each foot.  During stair ascent, the Proprio Foot resulted in a higher inter-limb symmetry than conventional prosthetic feet, with significant differences between the Proprio and SACH/SAFE feet.  The swing-phase dorsiflexion appeared to promote greater inter-limb symmetry because it facilitated forward motion of the body, resulting in a heel-to-toe center of pressure trajectory.  During stair descent, all feet had low symmetry without significant differences between feet.  The movement strategy used when descending stairs, which was to roll over the edge of a step, had a greater influence on symmetry than the dorsiflexion features of prosthetic feet.  The authors concluded that individuals with unilateral TTA who function at either K-Level-2 or K-Level-3 and have to negotiate stairs on a regular basis, within their home, community, or work environment, may benefit from the use of the Proprio Foot or other microprocessor-controlled feet that allow active dorsiflexion during swing.

The authors stated that this study had several drawbacks.  The altered strategies employed by the subjects while descending stairs suggested the possibility of work calculation limitations only for this task because of the shortcomings of current in-sole sensor technology.  Since the F-scan sensors were capable of measuring only the normal forces applied to the sensor, movement of the prosthetic foot over the edge of the step may have resulted in GRFs having a substantial shear component.  The SEW results during stair descent should therefore be interpreted and weighed appropriately.  This strategy of rolling over the edge of the step during stair descent presented a significant challenge in the measurement of GRFs with commercially available instrumentation.  However, with some error, the SEW measure was able to quantify the asymmetry that was apparent during stair descent.  An advantage of determining inter-limb symmetry with measures like the SEW -- as opposed to comparing movement kinetics in subjects without amputation -- was the ability to quantify similarity in strategies used by the intact and prosthetic limbs to move the body during the stair negotiation.  The absence of motion-capture data restricted the ability to determine the joint kinematics, which limited the discussion to clinical observation and findings published in the literature.  All prosthetic fitting and alignment procedures were performed by the same board-certified prosthetist using standard protocols as stated in the manufacturer’s technical manual.  At the time of data collection, there were no commercially available, reliable, and valid devices that could quantify dynamic alignment of a prosthetic foot.

Struchkov and Buckley (2016) noted that walking down slopes and/or over uneven terrain is problematic for unilateral TTAs.  Accordingly, “ankle” devices have been added to some dynamic-response feet.  This study examined if the use of a microprocessor controlled (MPC) passive-articulating hydraulic ankle-foot device improved the gait biomechanics of ramp descent in comparison to conventional ankle-foot mechanisms.  A total of 9 active unilateral TTA repeatedly walked down a 5° ramp, using a hydraulic ankle-foot with microprocessor active or inactive or using a comparable foot with rubber ball-joint (elastic) “ankle” device.  When inactive the hydraulic unit's resistances were those deemed to be optimum for level-ground walking, and when active, the plantar- and dorsi-flexion resistances switched to a ramp-descent mode.  Residual limb kinematics, joints moments/powers and prosthetic foot power absorption/return were compared across ankle types using ANOVA.  Foot-flat was attained fastest with the elastic foot and second fastest with the active hydraulic foot (p < 0.001).  Prosthetic shank single-support mean rotation velocity (p = 0.006), and the flexion (p < 0.001) and negative work done at the residual knee (p = 0.08) were reduced, and negative work done by the ankle-foot increased (p < 0.001) when using the active hydraulic compared to the other 2 ankle types.  The authors concluded that the greater negative “ankle” work done when using the active hydraulic compared to other 2 ankle types, explained why there was a corresponding reduction in flexion and negative work at the residual knee.  They stated that these findings suggested that use of a microprocessor controlled hydraulic foot would reduce the biomechanical compensations used to walk down slopes.

The authors stated that this study had several drawbacks.  First, with only 1 force platform within the ramp system, only trials where the prosthetic limb landed on the force platform were undertaken.  Expanding the protocol to include trials in which the intact limb landed on the platform would have increased the likelihood of participants becoming fatigued.  These researchers  chose to remotely “trigger” the MPC foot into its “ramp descent” mode using Bluetooth connection to the device.  Although this is not what would happen when such a device is used in the “real world”, these investigators felt that it was more important to assess the effects of the hydraulic resistance alterations associated with the device's “ramp descent” mode, rather than to test if and when switching to this mode occurred.  Second, all participants were familiarized to using either an Elan or Echelon VT foot, both of which were hydraulic ankle-foot devices.  Although these investigators found that the type of habitual foot participants used had minimal effect on results, having only 20 mins to become familiar with the non-hydraulic Epirus foot may mean the issue of familiarity is a confounding factor.  The relatively short familiarization period may explain why certain parameters investigated returned relatively high group standard deviation values.  Finally, there was no comparison of ramp-descent with a non-articulating (rigid ankle) prosthetic ankle-foot.  This was because it was felt that a 4rth foot condition would be problematic due to potential fatigue issues for participants, and/or that the biomechanical compensation required when using such feet might have “carry-over” effects to the other foot conditions, especially as all participants habitually used an articulating ankle-foot device.

Pro-Flex Foot

Childers and Takahashi (2018) stated that prosthetic feet are designed to store energy during early stance and then release a portion of that energy during late stance.  The usefulness of providing more energy return depends on whether or not that energy transfers up the lower limb to aid in whole body propulsion.  These researchers examined how increasing prosthetic foot energy return affected walking mechanics across various slopes.  A total of 5 individuals with a unilateral TTA walked on an instrumented treadmill at 1.1 m/s for 3 conditions (level ground, +7.5°, −7.5°) while wearing a prosthetic foot with a novel linkage system and a traditional energy storage and return foot.  The novel foot (NF) demonstrated greater range of motion (ROM; p = 0.0012), and returned more energy (p = 0.023) compared to the traditional foot.  The increased energy correlated with an increase in center of mass (CoM) energy change during propulsion from the prosthetic limb (p = 0.012), and the increased prosthetic limb propulsion correlated to a decrease in CoM energy change (i.e., collision) on the sound limb (p < 0.001).  The authors concluded that these findings showed that this NF was able to return more energy than a traditional prosthetic foot and that this additional energy was used to increase whole body propulsion.  They stated that the novel linkage system in the Pro-Flex foot allowed it to have more ROM and better conform to different slopes.  The Pro-Flex foot was able to leverage its additional ROM to absorb and return more energy than the more traditional Vari-Flex foot.  The additional energy return from the Pro-Flex foot translated up the kinematic chain to effect the whole body CoM in such a way that it enabled more energy for propulsion than the Vari-Flex foot.  There was a significant inverse relationship between increasing CoM energy change during propulsion from the amputated limb and negative work absorbed by the sound limb during collision with the Pro-Flex foot and this rendered some support that the Pro-Flex foot has promise to reduce sound limb loading.  However, there were no other differences in other variables that correlated with reducing the risk of developing knee osteoarthritis, most likely due to the low sample size and low statistical power.

Heitzmann and colleagues (2018) noted that persons with TTA showed a greater peak prosthetic ankle power (push- off) when using energy storing and returning (ESAR) prosthetic feet as compared to solid-ankle cushion-heel feet.  ESAR feet further contribute to the users' body support and thus limit prosthetic ankle motion.  To improve ankle motion, articulating prosthetic feet have been introduced.  However, articulating feet may diminish push-off.  These investigators examined if a novel prosthetic foot, with a serial layout of carbon fiber leaf springs, connected by a multi-center joint construction, has advantages in kinematics and kinetics over a conventional ESAR prosthetic foot.  A total of 11 individuals with unilateral TTA were fitted with the NF and a conventional ESAR Foot (CF) and underwent 3-D gait analysis.  As an additional power estimate of the prosthetic ankle, a unified, deformable, segment (UD) model approach was applied; 11 matched individuals without impairments served as a reference.  The NF showed an effective prosthetic ankle ROM that was closer to a physiologic ankle ROM, at 31.6° as compared to 15.2° with CF (CF versus NF, p = 0.003/NF versus reference, p = 0.171) without reducing the maximum prosthetic ankle joint moment.  Furthermore, the NF showed a great increase in prosthetic ankle power (NF 2.89 W/kg versus CF 1.48 W/kg CF versus NF p < 0.001) and a reduction of 19 % in the peak knee varus moment and 13 % in vertical ground reaction forces on the sound side for NF in comparison to CF.  The authors concluded that the NF showed that serial carbon fiber leaf springs, connected by a multi-center joint construction provided a larger ankle joint ROM and higher ankle power than a conventional carbon fiber structure alone.  Consequently, load was taken off the contralateral limb, as measured by the decrease in vertical ground reaction forces and peak knee varus moment.

The authors stated that this study had several drawbacks.  The different accommodation times of 2 weeks for the CF and only 30 to 45 mins for the re-fitted NF may have affected the results.  As NF was a pilot production product, these researchers had no experience with the product, but decided to have initial trials with the NF in a controlled environment, and therefore abandoned a 2-week accommodation.  However, these investigators thought that a satisfactory accommodation period for NF was given as the subjects could get accustomed to it in various terrains.  Another potential drawback of the study was the fixed order of measurements (NF first; CF second).  This conceivably may have introduced a bias, but these measurement conditions were chosen due to a number of practical reasons increasing the feasibility of this study, as well as ensuring that removing and replacing markers between experimental conditions was not necessary.  Individuals who has had a TTA walked slightly, but significantly slower with the NF (0.06 m/s) compared to CF and differences in kinetics may thus be attributed to speed as a confounding factor.  Since a violation of normal distribution could occasionally be accepted in parametric tests, the authors retrospectively compared kinetics using a multi-variate analysis of co-variance (MANCOVA), with speed as a co-variate.  This retrospective analysis confirmed the results of the original, non-parametric statistical analysis (peak dorsi plantar flexion power conventional model NF 2.89 ± 0.90, CF 1.48 ± 0.35 W/kg, p < 0.001; UD model NF 2.77 ± 0.70, CF 2.12 ± 0.49 W/kg, p = 0.002).  Thus, these researchers were confident that the differences in kinetics reflected the effects of the feet not the difference in walking speed.

Appendix

Clinical assessments of a member’s rehabilitation potential should be based on the following classification levels: 

This expectation of functional ability information must be clearly documented and retained in the prosthetist's records. The simple entry of a K modifier in those records is not sufficient. For K3 or above functional levels, there must be documented evaluation from physical therapist to establish functional levels and activities. There must be information about the member’s history and current condition that supports the designation of the functional level by the prosthetist and physical therapist.

For medically necessary frequency of replacement of prosthetics, see Medi-Cal. Orthotics and prosthetics. Frequency limits on prosthetics. Ortho cd fre 2. Provider Manual. Sacramento, CA: California Department of Health Care Services; August 2010. Available at: Medi-Cal:Provider Manuals. Accessed August 15, 2012.

Note: Consistent with DME MAC policy, when an initial below knee prosthesis (L5500) or a preparatory below knee prosthesis (L5510-L5530, L5540) is provided, prosthetic substitutions and/or additions of procedures and components are considered medically necessary in accordance with the functional level assessment except for codes L5629, L5638, L5639, L5646, L5647, L5704, L5785, L5962, and L5980 which will be considered not medically necessary. K-3 and higher level feet are considered not medically necessary with a preparatory prosthesis.

• Addition to lower extremity, below knee, acrylic socket (L5629)
• Addition to lower extremity, below knee, leather socket (L5638)
• Addition to lower extremity, below knee, wood socket (L5639)
• Addition to lower extremity, below knee, air-fluid, gel or equal, cushion socket (L5646)
• Addition to lower extremity, below knee suction socket (L5647)
• Custom shaped protective cover, below knee (L5704)
• Addition, exoskeletal system, below knee, ultra-light material (titanium, carbon fiber or equal) (L5785)
• Addition, endoskeletal system, below knee, flexible protective outer surface covering system (L5962)
• All lower extremity prostheses, flex foot system (L5980)

Consistent with DME MAC policy, when a below knee preparatory prefabricated prosthesis (L5535) is provided, prosthetic substitutions and/or additions of procedures are considered medically necessary in accordance with the functional level assessment except for codes L5620, L5629, L5645, L5646, L5670, L5676, L5704, and L5962 which will be considered not medically necessary. K-3 and higher level feet are considered not medically necessary with a preparatory prosthesis.

• Addition to lower extremity, test socket, below knee (L5620)
• Addition to lower extremity, below knee, acrylic socket (L5629)
• Addition to lower extremity, below knee, flexible inner socket, external frame (L5645)
• Addition to lower extremity, below knee, air, fluid, gel or equal, cushion socket (L5646)
• Addition to lower extremity, below knee, molded supracondylar suspension ('PTS' or similar) (L5670)
• Addition to lower extremity, below knee, knee joints, single axis, pair (L5676)
• Custom shaped protective cover, below knee (L5704)
• Addition, endoskeletal system, below knee, flexible protective outer surface covering system (L5962)

Consistent with DME MAC policy, when an above knee initial prosthesis (L5505) or an above knee preparatory (L5560-L5580, L5590-L5600) prosthesis is provided, prosthetic substitution and/or additions of procedures and components are considered medically necessary in accordance with the functional level assessment except for codes L5610, L5631, L5640, L5642, L5644, L5648, L5705, L5706, L5964, L5980, and L5710-L5780, L5790-L5795 which will be considered not medically necessary. K-3 and higher level feet are considered not medically necessary with a preparatory prosthesis.

• Addition to lower extremity, endoskeletal system, above knee, hydracadence system (L5610)
• Addition to lower extremity, above knee or knee disarticulation, acrylic socket (L5631)
• Addition to lower extremity, knee disarticulation, leather socket (L5640)
• Addition to lower extremity, above knee, leather socket (L5642)
• Addition to lower extremity, above knee, wood socket (L5644)
• Addition to lower extremity, above knee, air, fluid, gel or equal, cushion socket (L5648)
• Custom shaped protective cover, above knee (L5705)
• Custom shaped protective cover, knee disarticulation (L5706)
• Addition, endoskeletal system, above knee, flexible protective outer surface covering system (L5964)
• All lower extremity prostheses, flex foot system (L5980)
• Addition, exoskeletal knee-shin system, single axis, manual lock (L5710)
• Additions, exoskeletal knee-shin system, single axis, manual lock, ultra-light material (L5711)
• Addition, exosketal knee-shin system, single exis, friction swing and stance phase control (safety knee) (L5712)
• Addition, exoskeletal knee-shin system, single axis, variable friction swing phase control (L5714)
• Addition, exoskeletal knee-shin system, polycentric, mechanical stance phase lock (L5716)
• Addition, exoskeletal knee-shin system, polycentric, friction swing and stance phase control (L5718)
• Addition, exosketal knee-shin system, single axis, pneumatic swing, friction stance phase control (L5722)
• Addition, exoskeletal knee-shin system, single axis, fluid swing phase control (L5724)
• Addition, exoskeletal knee-shin system, single axis, external joints fluid swing phase control (L5726)
• Addition, exoskeletal knee-shin system, single axis, fluid swing and stance phase control (L5728)
• Addition, exoskeletal knee-shin system, single axis, pneumatic/hydra pneumatic swing phase control (L5780)
• Addition, exoskeletal system, above knee, ultra-light material (titanium, carbon fiber or equal) (L5790)
• Addition, exoskeletal system, hip disarticulation, ultra-light material (titanium, carbon fiber or equal) (L5795) 

Consistent with DME MAC policy, when an above knee preparatory prefabricated prosthesis (L5585) is provided, prosthetic substitution and/or additions of procedures and components are considered medically necessary in accordance with the functional level assessment except for codes L5624, L5631, L5648, L5651, L5652, L5705, L5706, L5964, and L5966 which will be considered not medically necessary. K-3 and higher level feet are considered not medically necessary with a preparatory prosthesis.

• Addition to lower extremity, test socket, above knee (L5624)
• Addition to lower extremity, above knee or knee disarticulation, acrylic socket (L5631)
• Addition to lower extremity, above knee, air, fluid, gel or equal, cushion socket (L5648)
• Addition to lower extremity, above knee, flexible inner socket, external frame (L5651)
• Addition to lower extremity, suction suspension, above knee or knee disarticulation socket (L5652)
• Custom shaped protective cover, above knee (L5705)
• Custom shaped protective cover, knee disarticulation (L5706)
• Addition, endoskeletal system, above knee, flexible protective outer surface covering system (L5964)
• Addition, endosketal system, hip disarticulation, flexible protective outser surface covering system (L5966) 

Codes for ultra-light materials may only be used when materials such as carbon fiber, fiberglass, Kevlar, or other advanced composite lamination materials are used in the fabrication of a socket for an endoskeletal prosthesis. They are not used for ultralight materials used in other components of a prosthesis – e.g., knee/shin system, pylon, ankle, foot, etc.