Search Results (127)

Background/Objectives: Lower-limb amputation significantly impacts autonomy and daily functioning. Microprocessor-controlled prosthetic knees (MPKs) improve mobility, safety, and quality of life compared with non-microprocessor prosthetic knees (nMPKs). Despite general benefits, differences among MPK models remain unclear. The goal of this investigation was to evaluate functional mobility and patient-reported outcomes in active transfemoral amputees using a new MPK (PROTEOR QUATTRO) compared with existing MPKs. Methods: In this multicenter cross-over clinical trial, active transfemoral amputees were assessed using patient-specific functional scales (PSFS), standardized locomotor capacity tests (6MWT, 10mWT, HAI, SAI) and satisfaction and quality-of-life questionnaires (PEQ-A, SF-36, ESAT). Biomechanical data collection was performed during walking test, to examine gait symmetry indices. Results: The QUATTRO MPK was associated with significantly higher PSFS scores, reflecting higher self-rated ability in performing chosen daily life activities compared with patient’s current prosthesis. Standardized locomotor tests revealed comparable performance between devices. Biomechanical analyses showed similar symmetry indices for QUATTRO and other MPKs. Patient-reported outcomes showed an improvement in physical health with QUATTRO, while overall satisfaction remained similar. Conclusions: QUATTRO improved patient-perceived ability to perform meaningful daily-life activities while maintaining comparable performance on standardized locomotor tests. These results highlight the importance of patient-centered assessments in identifying functional benefits that may guide individualized prosthetic prescriptions for active transfemoral amputees. Full article

Background: Lower limb prosthesis users commonly exhibit gait asymmetry that may increase metabolic demand. Gait asymmetry, therefore, is frequently targeted in rehabilitation to improve walking efficiency. This review aimed to investigate whether interventions that improve gait asymmetry reduce metabolic demand in unilateral lower limb prosthesis users. Methods: A search of relevant English-language articles was conducted using PubMed and CINAHL, yielding a total of 1067 records. Following title, abstract, and full-text screening, 10 studies met eligibility requirements and were included in the qualitative synthesis. Data extraction focused on participant characteristics, gait asymmetry measures, metabolic outcomes, and intervention characteristics. Results: Four main intervention categories were identified: advanced prosthetic knees and ankles, prosthetic mass manipulation, feedback-based gait interventions, and exercise-based training. Across studies, changes in gait symmetry were not consistently associated with reductions in metabolic demand. Interventions targeting ankle function showed the most consistent reductions in metabolic demand, particularly during demanding walking tasks. In contrast, distal prosthetic mass addition consistently increased metabolic demand and worsened gait symmetry. Conclusion: Current evidence does not support a consistent or direct relationship between gait symmetry and metabolic demand in lower limb prosthesis users. Gait asymmetry may not be inherently metabolically disadvantageous and may represent an energetically optimal adaptation. Full article

Background: The natural motion of the human knee involves a combination of rotation and translation, resulting in a variable Instantaneous Center of Rotation (ICR) throughout the gait cycle. Traditional prosthetic knee designs often fail to reproduce this complex kinematic behavior. Objectives: This study aims to propose a customized, biomimetic knee mechanism through the synthesis of a four-bar linkage capable of approximating the physiological ICR trajectory with high precision. Methods: A Genetic Algorithm (GA) was implemented to optimize the geometric parameters of the four-bar mechanism, specifically its link lengths and inter-link angles. The optimization process is based on Freudenstein’s equation, which analytically relates the input and output angles of the linkage to the lengths of its links. The desired ICR trajectory was derived from experimental data, and the objective function minimized the Euclidean error between the generated and target trajectories. Results: The proposed method yielded customized mechanisms that closely approximate the target ICR curves, achieving an overall mean Euclidean tracking error of 1.95% (±1.68%) across diverse patient profiles, with a best-case optimization error as low as 0.355%. Furthermore, the GA demonstrated high computational efficiency, converging on optimal geometric configurations in an average execution time of just 3.98 min. Conclusions: These numerical results validate the robustness of the GA in navigating the design space while strictly adhering to kinematic constraints, Grashof’s condition, and anatomical motion limits. The integration of Freudenstein’s equation with GA-based optimization techniques enables the customized synthesis of four-bar linkages with a high capacity to reproduce the physiological kinematics of the knee. This computational approach could be highly beneficial for the design of polycentric knee prostheses, as it reduces design and manufacturing time by providing the initial parameters for the development of the four-bar mechanism, ultimately ensuring a better biomechanical fit between prosthetic and natural human movement. Full article

Background/Objectives: Ankle dorsiflexion plays a fundamental role in gait stability, impact absorption, and the stance-to-swing transition, and its impairment is a major limitation in transtibial prostheses. This study proposes and evaluates a lightweight two-stage pipeline for generating ankle-dorsiflexion references using a single shank-mounted inertial measurement unit (IMU). Methods: In the first stage, a deep neural network (DNN) estimates the shank pitch waveform from raw three-axis accelerations and angular velocities. In the second stage, the estimated shank pitch is transformed into an ankle-dorsiflexion waveform using a temporal mapping model. The approach was evaluated on a multisubject subset of the NONAN GaitPrint database comprising 35 healthy young adults, 598 walking trials, and approximately 122,468 gait cycles, using a strict subject-held-out protocol. Results: A feature-based Random Forest baseline showed limited performance, whereas the waveform-based DNN achieved high accuracy for shank pitch estimation, with test R² values up to 0.97. A conventional polynomial mapping between shank pitch and dorsiflexion yielded weak performance, whereas a temporal mapping model substantially improved the estimation of ankle dorsiflexion, with test R² values up to 0.85. The resulting ankle reference was integrated into a Gazebo/Robot Operating System 2 (ROS 2) simulation of a transtibial prosthesis, where the generated trajectories were executed in a software integration test under open-loop position control, confirming stable and consistent trajectory execution. Conclusions: These results indicate that combining accurate shank pitch estimation with temporal mapping enables feasible ankle-dorsiflexion reference generation from a single sensor in able-bodied gait, offering a preliminary, simulation-based pathway for single-sensor artificial intelligence (AI) pipelines in prosthetic development. The framework supports waveform-level feasibility, not clinical readiness or functional prosthetic control. Full article

Background: The Mercer Universal Prosthesis (MUP), designed with a default “neutral” (vertical) socket alignment, was developed to simplify transtibial prosthetic fitting, reduce labor costs, and improve access to prosthetic care in low-resource settings. Methods: This present longitudinal study evaluated biomechanical and functional outcomes at baseline, 6 months, and 12 months in 20 transtibial amputees fitted with the MUP. Results: Functional outcomes, assessed using the SF-36, showed significant improvement in overall health scores at 12 months (p < 0.001), while physical function and energy/fatigue domains remained unchanged (p = 0.686 and p = 0.211, respectively). Biomechanically, sagittal kinematics, measured using inertial motion capture, revealed significant limb × time interactions for hip flexion, knee flexion, and ankle plantarflexion. At 6 months, maximum hip flexion (−7°, p = 0.008) and knee flexion (−11°, p = 0.005) of the prosthetic limb were decreased versus baseline. At 12 months, the only observed difference was increased maximum ankle plantarflexion of the intact limb (+5° vs. baseline, p = 0.016). Muscle effort, quantified via the integral of EMG throughout the gait cycle, did not differ significantly between prosthetic and intact limbs across time points. Gait symmetry index (GSI) scores for hip, knee, and ankle range of motion trended toward gradual improvement but without statistical significance (p > 0.05). Conclusions: The MUP performance was maintained over 12 months, with stable biomechanical performance and meaningful quality-of-life gains. These findings support its potential as a cost-effective solution to expand prosthetic accessibility in low- and middle-income countries. Full article

This study investigated the feasibility and biomechanical effects of volitional electromyography (EMG)-based control of a powered transtibial ankle prosthesis. Four male participants completed static and dynamic EMG assessments and gait analysis while using both their prescribed passive prosthesis and an EMG-controlled powered prototype during level walking at self-selected and fast speeds, as well as ramp ascent and descent. Selective activation of residual tibialis anterior and gastrocnemius muscles was quantified using a co-contraction index, and lower-limb kinematics and kinetics were compared between prosthetic conditions. Participants were able to generate task-dependent residual muscle activity, supporting the feasibility of EMG-based volitional control. However, muscle selectivity was reduced during dynamic tasks, with higher co-contraction during gait than during seated static contractions, and substantial inter-subject variability was observed. Compared to the prescribed passive prosthesis, the EMG-controlled prototype generally produced lower prosthetic-side ankle range of motion and ankle power, although ankle moments were sometimes slightly greater. These findings suggest that EMG control is feasible, but that future controller design must remain flexible to individual users’ neuromuscular abilities and dynamic control limitations. The results provide important guidance for the development and testing of more adaptive, personalized, and functionally effective EMG-controlled prosthetic ankle systems. Full article

Magnetorheological (MR) dampers enable semi-active control in prosthetic knees by providing rapidly adjustable resistance with low mechanical complexity. This paper evaluates three torque level control methodologies for a transfemoral prosthetic leg incorporating an MR damper: a model-based feedforward strategy, an adaptive inverse-dynamics controller, and a robust inverse-dynamics controller. A Lagrange-based planar leg model with explicit force-to-torque mapping is formulated, and a reference knee trajectory is estimated from measurable gait variables using a cubic polynomial model whose order is selected through least-squares RMSE analysis. Each controller is assessed using knee-angle tracking accuracy and control effort to capture the practical trade-off between motion quality and energy demand. Results demonstrated that the adaptive inverse-dynamics controller has the smallest tracking error but requires the highest effort, whereas the robust inverse-dynamics approach realizes approximately the same tracking performance with reduced effort, thereby suggesting the best accuracy–effort compromise in the present work. Results, likewise, examined actuator feasibility by considering the MR damper as the primary dissipative element and the DC motor as a supplemental active actuator required when damping alone cannot satisfy the commanded knee torque. Full article

Lower-limb amputation remains a significant clinical and socio-economic challenge, while the high cost of microprocessor-controlled prostheses (MPKs) limits their widespread accessibility. This paper presents the design and preliminary laboratory-scale evaluation of a low-cost microprocessor-controlled ankle prosthesis intended as a feasibility-oriented alternative platform for future active prosthetic system development. Building upon the previously developed V1 mechanical architecture, an updated CAD model was created in the SolidWorks 2024 environment, and the kinematic configuration was refined using a ball-screw transmission (SFU1204-300) driven by a NEMA 17 stepper motor. The electronic control system integrates an ESP32 microcontroller, an MPU9250 inertial measurement unit (IMU), a limit switch for initial-position detection, and a WiFi-based REST API interface for communication and control. Laboratory no-load experiments demonstrated controlled positional behavior, repeatable angular response, and successful operation of the homing procedure within a motion range of 0–4200 motor steps. The prototype actively generated dorsiflexion–plantar flexion motion in the sagittal plane, while a passive inversion–eversion mechanism was incorporated and intended to improve structural adaptability. IMU-based measurements enabled preliminary monitoring of angular displacement and positional behavior during the experiments. The presented prototype represents an initial engineering feasibility study of a low-cost active ankle actuation architecture and provides a foundation for future investigations involving load-bearing experiments, biomechanical gait analysis, and closed-loop control implementation. Full article

Background/Objectives: The modern prosthetic foot market is characterized by a pronounced polarization between affordable but low-function devices and high-performance yet costly composite prostheses. The aim of this study was to develop and comprehensively evaluate cost-effective, functional prosthetic feet manufactured by fused deposition modeling (FDM). Methods: An iterative design methodology was employed, combining finite element analysis to optimize the biomechanical response of the device, the incorporation of user-specific requirements and experimental validation. Two TPU 95A-based 3D-printed prosthetic foot designs were designed and developed, and their strength and functional characteristics were assessed numerically under the ISO 22675:2024 normative loading cycle. Bench-top mechanical tests were conducted on the fabricated prototypes. Functional performance was evaluated by a transtibial amputee using an inertial motion capture system to analyze gait kinematics. Results: The results demonstrated that both designs operate predominantly within the elastic range with an adequate safety margin. The pilot feasibility gait assessment indicated feasibility and plausibility within the tested protocol and participant for both prototypes. Conclusions: The developed TPU 95A-based FDM prosthetic feet demonstrated promising structural integrity and functional feasibility, supporting the potential of low-cost additive manufacturing as a viable approach for producing affordable prosthetic feet. Further studies with larger participant cohorts and extended testing are needed to confirm clinical applicability and long-term performance. Full article

Background/Objectives: Prosthesis optimization after transfemoral amputation is often guided by clinical experience, yet quantitative evidence isolating how prosthesis mass, inertial properties, and alignment affect mechanical load transmission remains limited. Musculoskeletal modeling can be used as a controlled framework for examining relative sensitivity rankings of constraint force transmission across prosthetic junctions under fixed gait inputs. Methods: A model was modified to incorporate a transfemoral prosthesis. Experimental walking data from a healthy adult reference subject (Qualisys motion capture, synchronized AMTI force plates) provided kinematics and ground reaction forces for model scaling, inverse kinematics, and loading. These inputs provided a standardized mechanical reference and were not intended to represent transfemoral amputee gait. Prosthesis mass (2.625, 3.50, 4.375 kg), inertia (0.5×, 1.0×, 1.5×), and mediolateral alignment (−10, 0, +10 mm) were varied while keeping kinematics and ground reaction forces identical across conditions. Constraint reaction forces at the socket–residual limb junction and prosthetic ankle were computed and normalized to body weight. Results: Increasing mass produced the largest monotonic increases in peak resultant constraint reactions, most prominently at the socket-level junction (8.51 → 10.48 → 12.29 BW), with smaller changes at the ankle and unchanged peak timing. Inertia caused joint-specific effects, whereas mediolateral alignment minimally affected constraint reaction forces and redistributed force components. Conclusions: This study quantified the one-factor-at-a-time effects of prosthesis mass, inertia, and mediolateral alignment on inter-segment constraint reaction forces. The reported reactions should be interpreted as net rigid-body constraint reactions under fixed inputs, not as physiological joint contact forces or direct interface loads. Full article

Background/Objectives: Bone-anchored prostheses provide an alternative to socket prostheses, directly connecting the prosthesis to the residual limb via osseointegration. However, limited evidence exists on how spatiotemporal gait parameters and gait symmetry change over time following osseointegration in individuals with unilateral transfemoral amputation. This study aimed to examine changes in spatiotemporal and gait symmetry parameters before osseointegration and at 6 and 12 months post-surgery. Methods: Common spatiotemporal parameters were collected from six individuals with unilateral transfemoral amputation at baseline (with socket prosthesis) and at 6 and 12 months post-osseointegration using a motion analysis system. Group-level differences were assessed using repeated measures ANOVA. Gait symmetry was evaluated using selected spatiotemporal parameters. Results: Following osseointegration, individuals with unilateral transfemoral amputation experienced significant spatiotemporal changes over time. At the group level, walking velocity and stride length decreased at 6 months, with stride length increasing at 12 months. Step width and prosthetic-side step length increased at 12 months relative to 6 months, while intact-side step length decreased. Prosthetic-side toe-off timing was shorter at 12 months. Gait symmetry responses varied individually: some with poor baseline symmetry improved, while those with better baseline symmetry became more asymmetric, indicating heterogeneous outcomes. Conclusions: This study highlights longitudinal changes in gait biomechanics following osseointegration in individuals with unilateral transfemoral amputation. Gait adaptations were highly variable across individuals and time points. Future research should involve larger, more homogeneous samples and incorporate kinetic, muscle activity, and functional outcome measures to better understand the impact of bone-anchored prostheses on gait and mobility. Full article

Background/Objectives: Choosing the best prosthetic foot for a patient is complicated by the many available options and limited evidence to distinguish them. This work aimed to clarify performance differences in the level-ground walking of K3-functional-level persons with amputations across a variety of prosthetic feet within the energy storage and return class. Methods: This clinical trial assessed 10 subjects fitted with the Ossur ProFlex foot (LP and XC) compared to their original foot after a 30-day adaptation period and careful prosthetic alignment matching. Multivariate data (walking performance, noise/play, balance and satisfaction) were collected in the gait laboratory. Results: Results were mixed across the cohort. MCID and statistical analysis were used to assess the magnitude and importance of the changes observed. Overall, the changes were small and not statistically significant. Conclusions: Our findings support that performance across a variety of measures for K3-level amputees walking over level ground is relatively insensitive to prosthetic foot componentry within the energy storage and return class. While functional performance is not the only metric that contributes to foot choice, it is an important one. This study helps to circumscribe its role in the larger decision-making framework for this class of componentry in persons with transtibial amputation. Full article

Background: Transtibial prostheses are commonly classified as endoskeletal or exoskeletal and differ in weight, adaptability, and mechanical response, which may influence gait performance. This study examined whether prosthesis type affects overground walking movement structure and neuromuscular control and assessed the relationship between walking speed and neuromuscular control. Methods: Principal component analysis (PCA) was applied to kinematic marker data from 20 unilateral transtibial amputees using either endoskeletal (n = 10; 54.7 ± 6.1 years) or exoskeletal prostheses (n = 10; 57.9 ± 8.7 years) during self-selected overground walking. Principal movements (PMs) were extracted to represent functionally meaningful gait components. Movement structure was evaluated using the relative explained variance of PM positions (rVAR), whereas neuromuscular control was quantified using the root mean square of PM accelerations (RMS; acceleration magnitude) and the number of zero crossings (N; regularity/predictability). Group differences were examined using covariate-adjusted analyses, controlling for preferred walking speed. Results: No significant differences in walking movement structure were found between prosthetic types. Unadjusted analyses suggested greater swing-phase acceleration (PM₂) and lower neuromuscular variability across PM₁–PM₄ in the endoskeletal group; however, these effects were no longer significant after adjusting for BMI and walking speed. Walking speed showed strong associations with neuromuscular control (p ≤ 0.003), with faster speeds linked to greater swing-phase acceleration and reduced variability. Conclusions: Walking movement structure and neuromuscular control were comparable between prosthetic types, while walking speed emerged as a key factor in gait evaluation among transtibial amputees. Full article

To address the limitations of current prosthetic knees that lack personalized adaptability to users’ gait characteristics and walking speeds, this study proposes a personalized gait parameter prediction–based speed-adaptive control method for a hybrid active–passive intelligent prosthetic knee (HAPK). The proposed system integrates a perceptron-based model to predict individualized gait parameters by mapping anthropometric data and walking speed to key points of the knee trajectory. A fuzzy logic–based damping control for the swing phase and a position–torque control for the stance extension phase are developed to achieve real-time adaptation to different walking speeds and user-specific biomechanics. The hybrid actuation system combines hydraulic damping and motor torque assistance to ensure both compliance and power delivery across gait phases. Experimental results from variable-speed walking tests demonstrate that the proposed control method improves gait symmetry indices—reducing stance and swing asymmetries by approximately 30–38%—and achieves smoother, more natural gait transitions compared to traditional fixed-gait control strategies. These findings validate the effectiveness of the proposed approach in achieving continuous, personalized, and speed-consistent gait control for intelligent prosthetic knees. Full article

Walking on compliant terrain presents a substantial challenge for individuals with lower-limb amputation, further elevating their already high risk of falling. While powered ankle–foot prostheses have demonstrated adaptability across speeds and rigid terrains, control strategies optimized for soft or compliant surfaces remain underexplored. This work experimentally validates an admittance-based control strategy that dynamically adjusts the quasi-stiffness of powered prostheses to enhance gait stability on compliant ground. Human subject experiments were conducted with three healthy individuals walking on two bilaterally compliant surfaces with ground stiffness values of 63 and $25{\displaystyle \frac{\mathrm{kN}}{\mathrm{m}}}$, representative of real-world soft environments. Controller performance was quantified using phase portraits and two walking stability metrics, offering a direct assessment of fall risk. Compared to a standard phase-variable controller developed for rigid terrain, the proposed admittance controller reduced short-term maximum Lyapunov exponents by an average of 7%, indicating improved local dynamic stability. These results support the potential of adaptive prostheses control to enhance gait stability on compliant surfaces, contributing to the development of more robust human–prosthesis interaction. Full article