Does a microprocessor-controlled prosthetic knee affect stair ascent strategies in persons with transfemoral amputation?

Comparing the lower limb joint biomechanics of the Power Knee, C-Leg and Rheo Knee during ramp and stair ambulation

One of the most significant developments in prosthetic knee technology has been the introduction of the Microprocessor-Controlled Prosthetic Knee (MPK). However, there is a lack of consensus over how different types of MPKs affect performance in different ambulation modes. In this study, we investigated the biomechanical differences in ramp and stair maneuvers when an individual with transfemoral amputation wears three commercial MPKs: the Össur Power Knee, the Össur Rheo Knee and the Ottobock C-Leg 4. The primary outcome variable for this study was the lower limb biological joint work, inclusive of the intact leg and prosthetic side hip. We hypothesized that (1) the Power Knee would result in lower biological work during ascent activities than the C-Leg and Rheo, both passive MPKs, and (2) the C-Leg and Rheo would result in lower biological work during descent activities than the Power Knee. During ramp ascent, the C-Leg was associated with lower biological joint work (p < 0.05) than the Power Knee. However, this relationship did not hold during stair ascent, where the Power Knee showed advantages for stair ascent with net reductions in biological joint work of 14.1% and 23.3% compared to the Rheo and C-leg, respectively. There were no significant differences in biological joint work between the knees during ramp and stair descent, indicating that choice of MPK may not be as important for descent activities. Our results demonstrate that differences are present between different types of MPKs during ascent activities which could prove useful in the prescription of these devices.

Volitional EMG Control Enables Stair Climbing with a Robotic Powered Knee Prosthesis

Existing controllers for robotic powered prostheses regulate the prosthesis speed, timing, and energy generation using predefined position or torque trajectories. This approach enables climbing stairs step-over-step. However, it does not provide amputees with direct volitional control of the robotic prosthesis, a functionality necessary to restore full mobility to the user. Here we show that proportional electromyographic (EMG) control of the prosthesis knee torque enables volitional control of a powered knee prosthesis during stair climbing. The proposed EMG controller continuously regulates knee torque based on activation of the residual hamstrings, measured using a single EMG electrode located within the socket. The EMG signal is mapped to a desired knee flexion/extension torque based on the prosthesis knee position, the residual limb position, and the interaction with the ground. As a result, the proposed EMG controller enabled an above-knee amputee to climb stairs at different speeds, while carrying additional loads, and even backwards. By enabling direct, volitional control of powered robotic knee prostheses, the proposed EMG controller has the potential to improve amputee mobility in the real world.

A Scientometric Analysis and Visualization of Prosthetic Foot Research Work: 2000 to 2022

This study aims to highlight recent research work on topics around prosthetic feet through a scientometric analysis and historical review. The most cited publications from the Clarivate Analytics Web of Science Core Collection database were identified and analyzed from 1 January 2000 to 31 October 2022. Original articles, reviews with full manuscripts, conference proceedings, early access documents, and meeting abstracts were included. A scientometric visualization analysis of the bibliometric information related to the publications, including the countries, institutions, journals, references, and keywords, was conducted. A total of 1827 publications met the search criteria in this study. The related publications grouped by year show an overall trend of increase during the two decades from 2000 to 2022. The United States is ranked first in terms of overall influence in this field (n = 774). The Northwestern University has published the most papers on prosthetic feet (n = 84). Prosthetics and Orthotics International has published the largest number of studies on prosthetic feet (n = 151). During recent years, a number of studies with citation bursts and burst keywords (e.g., diabetes, gait, pain, and sensor) have provided clues on the hotspots of prosthetic feet and prosthetic foot trends. The findings of this study are based on a comprehensive analysis of the literature and highlight the research topics on prosthetic feet that have been primarily explored. The data provide guidance to clinicians and researchers to further studies in this field.

Whole body movement strategies during sit-to-stand and stair ascent in individuals with a lower limb amputation: A systematic review

BACKGROUND

Individuals with a lower limb amputation use compensatory strategies during essential tasks such as sit-to-stand and stair ascent leading to secondary physical conditions. The ensuing biomechanical parameters outlining the motion strategies they put in place need to be identified and described.

METHODS

We searched three databases (Embase, IEEE Xplore and PubMed) for articles on the spatiotemporal, the kinematics and the kinetics that compared the amputated, the intact lower limbs, or the trunk of individuals with a unilateral transtibial or transfemoral amputation with the limbs of a control group.

FINDINGS

We found twenty articles. During sit-to-stand, individuals with a lower limb amputation increased the trunk inclination angle toward the intact lower limb, explaining higher ground reaction forces and peak knee sagittal power generation. During stair ascent, individuals with a lower limb amputation increased the stance phase duration on the intact lower limb. Moreover, individuals with a lower limb amputation increased both lower limbs hip extension moment and power, and the amputated lower limb knee extension moment. In both tasks, the individuals with a transfemoral amputation presented larger differences than those with transtibial compared to the control group.

INTERPRETATION

Both lower limbs intact joint moment and power were increased to compensate for the prosthesis passive joint and to ensure stability. Stair gait studies mainly focused on the lower limbs' biomechanical changes in the sagittal plane, while sit-to-stand studies focused on asymmetries without comparing the lower limbs independently. Better methodological descriptions are essential to enhance the external validity of previous results.

Functional Mobility Training With a Powered Knee and Ankle Prosthesis

Limb loss at the transfemoral or knee disarticulation level results in a significant decrease in mobility. Powered lower limb prostheses have the potential to provide increased functional mobility and return individuals to activities of daily living that are limited due to their amputation. Providing power at the knee and/or ankle, new and innovative training is required for the amputee and the clinician to understand the capabilities of these advanced devices. This protocol for functional mobility training with a powered knee and ankle prosthesis was developed while training 30 participants with a unilateral transfemoral or knee disarticulation amputation at a nationally ranked physical medicine and rehabilitation research hospital. Participants received instruction for level-ground walking, stair climbing, incline walking, and sit-to-stand transitions. A therapist provided specific training for each mode including verbal, visual, and tactile cueing along with patient education on the functionality of the device. The primary outcome measure was the ability of each participant to demonstrate independence with walking and sit-to-stand transitions along with modified independence for stair climbing and incline walking due to the use of a handrail. Every individual was successful in comfortable ambulation of level-ground walking and 27 out of 30 were successful in all other functional modes after participating in 1–3 sessions of 1–2 h in length (3 terminated their participation before attempting all activities). As these prosthetic devices continue to advance, therapy techniques must advance as well, and this paper serves as education on new training techniques that can provide amputees with the best possible tools to take advantage of these powered devices to achieve their desired clinical outcomes.

Robot-mediated overground gait training for transfemoral amputees with a powered bilateral hip orthosis: a pilot study

Background

Transfemoral amputation is a serious intervention that alters the locomotion pattern, leading to secondary disorders and reduced quality of life. The outcomes of current gait rehabilitation for TFAs seem to be highly dependent on factors such as the duration and intensity of the treatment and the age or etiology of the patient. Although the use of robotic assistance for prosthetic gait rehabilitation has been limited, robotic technologies have demonstrated positive rehabilitative effects for other mobility disorders and may thus offer a promising solution for the restoration of healthy gait in TFAs. This study therefore explored the feasibility of using a bilateral powered hip orthosis (APO) to train the gait of community-ambulating TFAs and the effects on their walking abilities.

Methods

Seven participants (46–71 years old with different mobility levels) were included in the study and assigned to one of two groups (namely Symmetry and Speed groups) according to their prosthesis type, mobility level, and prior experience with the exoskeleton. Each participant engaged in a maximum of 12 sessions, divided into one Enrollment session, one Tuning session, two Assessment sessions (conducted before and after the training program), and eight Training sessions, each consisting of 20 minutes of robotically assisted overground walking combined with additional tasks. The two groups were assisted by different torque-phase profiles, aiming at improving symmetry for the Symmetry group and at maximizing the net power transferred by the APO for the Speed group. During the Assessment sessions, participants performed two 6-min walking tests (6mWTs), one with (Exo) and one without (NoExo) the exoskeleton, at either maximal (Symmetry group) or self-selected (Speed group) speed. Spatio-temporal gait parameters were recorded by commercial measurement equipment as well as by the APO sensors, and metabolic efficiency was estimated via the Cost of Transport (CoT). Additionally, kinetic and kinematic data were recorded before and after treatment in the NoExo condition.

Results

The one-month training protocol was found to be a feasible strategy to train TFAs, as all participants smoothly completed the clinical protocol with no relevant mechanical failures of the APO. The walking performance of participants improved after the training. During the 6mWT in NoExo, participants in the Symmetry and Speed groups respectively walked 17.4% and 11.7% farther and increased walking speed by 13.7% and 17.9%, with improved temporal and spatial symmetry for the former group and decreased energetic expenditure for the latter. Gait analysis showed that ankle power, step width, and hip kinematics were modified towards healthy reference levels in both groups. In the Exo condition metabolic efficiency was reduced by 3% for the Symmetry group and more than 20% for the Speed group.

Conclusions

This study presents the first pilot study to apply a wearable robotic orthosis (APO) to assist TFAs in an overground gait rehabilitation program. The proposed APO-assisted training program was demonstrated as a feasible strategy to train TFAs in a rehabilitation setting. Subjects improved their walking abilities, although further studies are required to evaluate the effectiveness of the APO compared to other gait interventions. Future protocols will include a lighter version of the APO along with optimized assistive strategies.

Effects of microprocessor-controlled prosthetic knees on self-reported mobility, quality of life, and psychological states in patients with transfemoral amputations

OBJECTIVE

This study aimed to determine the effects of the microprocessor-controlled prosthetic knee (MPK) joint on self-mobility, body perceptions, depression, and quality of life in patients with unilateral transfemoral amputations (TFAs).

METHODS

Thirty consecutive patients (28 males, mean age=38.5 years, age range=22-57) who had previously used non-MPKs and who were approved to use swing and stance phase-control MPKs were included in this 12-week clinical study. Before the MPK use and after the three-month follow-up, prosthetic use and locomotor capabilities were evaluated using the Houghton Scale and the Locomotor Capabilities Index (LCI-5), respectively. Body perception was assessed using the Amputee Body Image Scale (ABIS). The depressive symptoms and quality of life were evaluated using the Beck Depression Inventory (BDI) score and the 36-Item Short- Form Health Survey (SF-36), respectively.

RESULTS

After MPK use, statistically significant ameliorations were observed in all outcome measures. The basic and advanced LCI-5 increased from 26.7±2.2 and 24.8±5.2 to 27.6±1.2 (p=0.007) and 27±2.1 (p=0.004), respectively. Houghton scores improved from 9±1 to 10.3±0.8 (p=0.000). The ABIS and BDI scores decreased from 43.2±10.9 and 5.7±6.6 to 37.1±8.9 (p=0.000) and 3.8±4.5 (p=0.015), respectively. Also, the SF-36 physical function and vitality subscales increased from 71.2±24.0 and 75.5±14.6 to 85.6±16.6 (p=0.001) and 81.7±14.1 (p=0.015), respectively.

CONCLUSION

MPK use provides significant improvements in the locomotor capabilities, quality of life, and activities of daily living to patients with TFAs as well as improves their body image perceptions and depressive symptoms.

LEVEL OF EVIDENCE

Level III, Self controlled study.

Motorized Biomechatronic Upper and Lower Limb Prostheses-Clinically Relevant Outcomes

People with major limb amputations are severely impaired when it comes to activity, body structure and function, as well as participation. Demographic statistics predict a dramatic increase of this population and additional challenges with their increasing age and higher levels of amputation. Prosthetic use has been shown to have a positive impact on mobility and depression, thereby affecting the quality of life. Biomechatronic prostheses are at the forefront of prosthetic development. Actively powered designs are now regularly used for upper limb prosthetic fittings, whereas for lower limbs the clinical use of actively powered prostheses has been limited to a very low number of applications. Actively powered prostheses enhance restoration of the lost physical functions of an amputee but are yet to allow intuitive user control. This paper provides a review of the status of biomechatronic developments in upper and lower limb prostheses in the context of the various challenges of amputation and the clinically relevant outcomes. Whereas most of the evidence regarding lower limb prostheses addresses biomechanical issues, the evidence for upper limb prostheses relates to activities of daily living (ADL) and instrumental ADL through diverse outcome measures and tools.

Functional performance differences between the Genium and C-Leg prosthetic knees and intact knees

Microprocessor prosthetic knees (MPKs) have advanced technologically, offering new features to decrease impairment and activity limitations for persons with transfemoral amputation (TFA). The Genium knee is functionally untested, and functional differences between it and intact knees are unknown. This study sought to determine whether Genium use improves functional performance compared with the C-Leg. A randomized experimental crossover design was used, with a cross-section of five nonamputee controls for comparison to normal. Twenty community-ambulating persons with TFA were trained and tested for accommodation with study components. All subjects (n = 25) were assessed using the Continuous-Scale Physical Functional Performance-10 (CS-PFP10) assessment. Subjects with TFA used both MPK systems. Genium use improved upper-body flexibility, balance, and endurance domain scores (7.0%-8.4%, p </= 0.05) compared with the C-Leg. Only in the endurance domain did Genium users score significantly lower than nonamputees (22.4%, p = 0.05). Comparing the C-Leg with nonamputees, CS-PFP10 total (2.0%-24.4%, p = 0.03) and all domains except upper-body strength were lower than nonamputees (-13.4% to -28.9%, p </= 0.05). Nonetheless, regardless of knee condition, subjects with TFAs did not equal or surpass nonamputees in any functional domain, suggesting room for improvements in TFA functional performance.

Crossover study of amputee stair ascent and descent biomechanics using Genium and C-Leg prostheses with comparison to non-amputee control

This study was a randomized crossover of stair ambulation of Transfemoral Amputees (TFAs) using the Genium and C-Leg prosthetic knees. TFAs typically have difficulty ascending and descending stairs, limiting community mobility. The objective of this study was to determine the relative efficacy of the Genium and C-Leg prostheses for stair ascent and descent, and their absolute efficacy relative to non-amputees. Twenty TFAs, and five non-amputees participated in the study. TFAs were randomized to begin the study with the Genium or C-Leg prosthesis. Informed consent was obtained from all participants prior to data collection and the study was listed on clinicaltrials.gov (#NCT01473662). After fitting, accommodation, and training, participants were asked to demonstrate their preferred gait pattern for stair ascent and descent and a step-over-step pattern if able. TFAs then switched prosthetic legs and repeated fitting, accommodation, training, and testing. An eight camera Vicon optical motion analysis system, and two AMTI force plates were used to track and analyze the participants' gait patterns, knee flexion angles, knee moment normalized by body weight, and swing time. For stair descent, no significant differences were found between prostheses. For stair ascent, Genium use resulted in: increased ability to use a step-over-step gait pattern (p=0.03), increased prosthetic side peak knee flexion (p<0.01), and increased swing duration (p<0.01). Changes in contralateral side outcomes and in knee moment were not significant. Overall the Genium knee decreased deficiency in gait patterns for stair ascent relative to the C-Leg, by enabling gait patterns that more closely resembled non-amputees.

When to biomechanically examine a lower-limb amputee: A systematic review of accommodation times

BACKGROUND

Hundreds of investigations examining biomechanical outcomes of various prostheses have been completed, but one question remains unanswered: how much time should an amputee be given to accommodate to a new prosthesis prior to biomechanical testing?

OBJECTIVE

To examine the literature for accommodation time given during biomechanical investigations to determine whether consensus exists.

STUDY DESIGN

Systematic review.

METHODS

A systematic search was completed on 7 January 2016 using PubMed and Scopus.

RESULTS

The search resulted in 156 investigations. Twenty-eight studies did not provide an accommodation or were unclear (e.g. provided a "break in period"), 5 studies tested their participants more than once, 25 tested only once and on the same day participants received a new prosthesis (median (range): above-knee: 60 (10-300) min; below-knee: 18 (5-300) min), and 98 tested once and gave a minimum of 1 day for accommodation (hip: 77 (60-180) days; above-knee: 42 (1-540) days; below-knee: 21 (1-475) days).

CONCLUSION

The lack of research specifically examining accommodation and the high variability in this review's results indicates that it remains undecided how much accommodation is necessary. There is a need for longitudinal biomechanical investigations to determine how outcomes change as amputees accommodate to a new prosthesis. Clinical relevance The results of this review indicate that little research has been done regarding lower-limb amputees accommodating to a new prosthesis. Improper accommodation could lead to increased variability in results, results that are not reflective of long-term use, and could cause clinicians to make inappropriate decisions regarding a prosthesis.

Analysis of clinically important factors on the performance of advanced hydraulic, microprocessor-controlled exo-prosthetic knee joints based on 899 trial fittings

The objective of this work is to evaluate whether clinically important factors may predict an individual's capability to utilize the functional benefits provided by an advanced hydraulic, microprocessor-controlled exo-prosthetic knee component.This retrospective cross-sectional cohort analysis investigated the data of above knee amputees captured during routine trial fittings. Prosthetists rated the performance indicators showing the functional benefits of the advanced maneuvering capabilities of the device. Subjects were asked to rate their perception. Simple and multiple linear and logistic regression was applied.Data from 899 subjects with demographics typical for the population were evaluated. Ability to vary gait speed, perform toileting, and ascend stairs were identified as the most sensitive performance predictors. Prior C-Leg users showed benefits during advanced maneuvering. Variables showed plausible and meaningful effects, however, could not claim predictive power. Mobility grade showed the largest effect but also failed to be predictive.Clinical parameters such as etiology, age, mobility grade, and others analyzed here do not suffice to predict individual potential. Daily walking distance may pose a threshold value and be part of a predictive instrument. Decisions based solely on single parameters such as mobility grade rating or walking distance seem to be questionable.

Detection of Prosthetic Knee Movement Phases via In-Socket Sensors: A Feasibility Study

This paper presents an approach of identifying prosthetic knee movements through pattern recognition of mechanical responses at the internal socket's wall. A quadrilateral double socket was custom made and instrumented with two force sensing resistors (FSR) attached to specific anterior and posterior sites of the socket's wall. A second setup was established by attaching three piezoelectric sensors at the anterior distal, anterior proximal, and posterior sites. Gait cycle and locomotion movements such as stair ascent and sit to stand were adopted to characterize the validity of the technique. FSR and piezoelectric outputs were measured with reference to the knee angle during each phase. Piezoelectric sensors could identify the movement of midswing and terminal swing, pre-full standing, pull-up at gait, sit to stand, and stair ascent. In contrast, FSR could estimate the gait cycle stance and swing phases and identify the pre-full standing at sit to stand. FSR showed less variation during sit to stand and stair ascent to sensitively represent the different movement states. The study highlighted the capacity of using in-socket sensors for knee movement identification. In addition, it validated the efficacy of the system and warrants further investigation with more amputee subjects and different sockets types.