Search Results (12)

Background/Objectives: Children with cerebral palsy (CP) often develop altered muscle architecture and calf muscle contractures. Orthotic immobilization aims to provide prolonged stretch to lengthen the muscle belly and muscle–tendon unit (MTU), but immobilization may also cause atrophy. This study investigated whether immobilization combined with periods of daily muscle activation has a different effect on calf muscle properties than continuous immobilization alone. Methods: Fourteen children with CP and equinus deformity (mean age: 9.9 ± 3.0 years; GMFCS Level I: 10, II: 4) were enrolled in a 12-week randomized controlled trial. Participants were allocated to one of two groups: continuous immobilization (23 h per day) with a dynamic ankle–foot orthosis (AFO), or a combined regimen consisting of immobilization (14 h) and a daily activity phase (10 h). Gastrocnemius medialis (GM) MTU properties, including muscle belly and Achilles tendon (AT) length, fascicle length, and muscle volume, among others, were assessed four times using three-dimensional (3D) freehand ultrasound. Results: Significant within-group increases in MTU and AT lengths were observed over time at both a 90° ankle position (p < 0.01) and a more dorsiflexed ankle position (4 Nm applied torque, p < 0.01). However, no significant group × time interactions were observed for any parameter. Conclusions: Contrary to our hypothesis, combining activity and immobilization did not confer additional benefits. Nevertheless, shorter orthosis-wearing time had the same effect on the MTU and could lead to improved compliance with orthosis treatment in CP. Larger trials are needed to support our findings. Full article

Background/Objectives: The simulation of human movement offers transformative potential for the design of medical devices, particularly in understanding the cause–effect dynamics in individuals with neurological or musculoskeletal impairments. This study presents a simulation-driven framework to determine the optimal ankle–foot orthosis (AFO) stiffness for mitigating the risk of ankle sprains due to excessive subtalar inversion during high-impact activities, such as landing from a free fall. Methods: We employed biomechanical simulations to assess the influence of translational stiffness on subtalar inversion control, given that inversion angles exceeding 25 degrees are strongly correlated with injury risk. Simulations were conducted using a musculoskeletal model with and without a passive AFO; the stiffness varied in three anatomical directions. A Design of Experiments (DoE) approach was utilized to capture nonlinear interactions among stiffness parameters. Results: The results indicated that increased translational stiffness significantly reduced inversion angles to safer levels, though direction–dependent effects were noted. Based on these insights, we developed a 4D visualization tool that integrates simulation data with an interactive color–coded interface to depict ”safe design” zones for various AFO stiffness configurations. This tool supports clinicians in selecting stiffness values that optimize both safety and functional performance. Conclusions: The proposed framework enhances clinical decision-making and engineering processes by enabling more accurate and individualized AFO designs. Full article

In maritime search and rescue small object detection, existing high-accuracy detection models face deployment challenges on UAV platforms due to limited computational capabilities, while existing lightweight models often fail to meet performance requirements, reducing the overall effectiveness of rescue operations. To overcome the difficulty of balancing lightweight design and detection accuracy, we propose Maritime Small Object Detection Transformer (MSO-DETR), a lightweight detection transformer model for small object detection in maritime search and rescue, based on an improved Real-Time Detection Transformer (RT-DETR) architecture. MSO-DETR employs StarNet as its backbone to reduce the computational cost with a slight drop in detection accuracy. In addition, the Dynamic-range Histogram Self-Attention (DHSA) mechanism is integrated with the Attention-based Intra-scale Feature Interaction (AIFI) module to construct DHAIFI, which enhances the model’s ability to perceive object features under challenging conditions such as sea surface reflections and wave interference. During the feature fusion phase, we propose the Scale-Tuned Enhanced Feature Fusion (STEFF) module, which integrates the improved Attentional Scale Sequence Fusion (ASF) structure with the newly designed Multi-Dilated Convolution Cross-Stage Partial (MDC_CSP) and Parallel Aggregation Downsampling (PAD) to enhance multi-scale aggregation and small object recognition while maintaining computational efficiency. Experimental results demonstrate that, in contrast to the baseline, MSO-DETR achieves significant model lightweighting, reducing parameters by 67.3% and GFLOPs by 46.5%, while maintaining detection accuracy on the SeaDronesSee dataset, with only a 0.1% decrease in mAP50 and a 0.5% improvement in mAP50:95. It also delivers comparable performance to the baseline on the AFO dataset. Full article

Passive Dynamic Ankle–Foot Orthoses (PD-AFOs) are medical devices prescribed to individuals with foot drop, a condition characterized by weakness of the ankle dorsiflexor muscles. PD-AFOs can store and release energy during the stance phase of the gait cycle, while supporting the foot in the swing phase. This study aimed at estimating the energetics of a novel fiberglass-reinforced polyamide custom PD-AFO in a population of mild foot drop patients. Eight PD-AFOs were designed and 3D-printed via selective laser sintering for eight participants with a unilateral foot drop condition. Lower limb kinematics and AFO flexion/extension were recorded during comfortable walking speed via skin marker-based stereophotogrammetry. The stiffness of each AFO was measured via an ad hoc experimental setup. The elastic work performed by the PD-AFO during gait was calculated as the dot product of the calf-shell resisting moment and the rotation angle. The average maximum energy stored by the calf-shell across all PD-AFOs was 0.013 ± 0.005 J/kg. According to this study, 3D-printed custom PD-AFOs made with fiberglass-reinforced polyamide can store some elastic energy, which is released to the ankle during push-off. Further studies should be conducted to assess the effect of this energy return mechanism in improving the gait of individuals with deficits of the ankle plantarflexor muscles. Full article

Ankle-foot orthoses (AFOs) have been commonly prescribed for stroke survivors with foot drop, but their impact on the contractions of paretic tibialis anterior (TA) and medial gastrocnemius (MG) has remained inconclusive. This study thus investigated the effect of AFOs on these muscle contractions in stroke survivors. The contractions of paretic TA and MG muscles were assessed in twenty stroke patients and compared between walking with and without AFOs, using a novel wearable dynamic ultrasound imaging and sensing system. The study found an increase in TA muscle thickness throughout a gait cycle (p > 0.05) and a significant increase in TA muscle surface mechanomyography (sMMG) signals during the pre- and initial swing phases (p < 0.05) when using an AFO. MG muscle thickness generally decreased with the AFO (p > 0.05), aligning more closely with trends seen in healthy adults. The MG surface electromyography (sEMG) signal significantly decreased during the initial and mid-swing phases when wearing an AFO (p < 0.05). The TA-MG co-contraction index significantly decreased during initial and mid-swing phases with the AFO (p < 0.05). These results suggest that AFOs positively influenced the contraction patterns of paretic ankle muscles during walking in stroke patients, but further research is needed to understand their long-term effects. Full article

Ankle–foot orthoses (AFOs) constitute medical instruments designed for patients exhibiting pathological gait patterns, notably stemming from conditions such as stroke, with the primary objective of providing support and facilitating rehabilitation. The present research endeavors to conduct a comprehensive review of extant scholarly literature focusing on mathematical techniques employed for the examination of AFO models. The overarching aim is to gain deeper insights into the biomechanical intricacies underlying these ankle–foot orthosis models from a mathematical perspective, while concurrently aiming to advance novel models within the domain. Utilizing a specified set of keywords and their configurations, a systematic search was conducted across notable academic databases, including ISI Web of Knowledge, Google Scholar, Scopus, and PubMed. Subsequently, a total of 23 articles were meticulously selected for in-depth review. These scholarly contributions collectively shed light on the utilization of nonlinear optimization techniques within the context of ankle–foot orthoses (AFOs), specifically within the framework of fully Cartesian coordinates, encompassing both kinematic and dynamic dimensions. Furthermore, an exploration of a two-degree-of-freedom AFO design tailored for robotic rehabilitation, which takes into account the interplay between foot and orthosis models, is delineated. Notably, the review article underscores the incorporation of shape memory alloy (SMA) elements in AFOs and overviews the constitutive elastic, viscoelastic, and hyperelastic models. This comprehensive synthesis of research findings stands to provide valuable insights for orthotists and engineers, enabling them to gain a mathematical understanding of the biomechanical principles underpinning AFO models and fostering the development of innovative AFO designs. Full article

In this investigation, the adaptive fractional-order non-singular fixed-time terminal sliding mode (AFoFxNTSM) control for the uncertain dynamics of robotic manipulators with external disturbances is introduced. The idea of fractional-order non-singular fixed-time terminal sliding mode (FoFxNTSM) control is presented as the initial step. This approach, which combines the benefits of a fractional-order parameter with the advantages of NTSM, gives rapid fixed-time convergence, non-singularity, and chatter-free control inputs. After that, an adaptive control strategy is merged with the FoFxNTSM, and the resulting model is given the label AFoFxNTSM. This is done in order to account for the unknown dynamics of the system, which are caused by uncertainties and bounded external disturbances. The Lyapunov analysis reveals how stable the closed-loop system is over a fixed time. The pertinent simulation results are offered here for the purposes of evaluating and illustrating the performance of the suggested scheme applied on a PUMA 560 robot. Full article

Ankle foot orthoses (AFOs) are medical devices prescribed to support the foot and ankle of drop-foot patients. Passive-dynamic AFOs (PD-AFOs) are an effective solution for less severe cases. While off-the-shelf PD-AFOs are rather inexpensive, they provide poor anatomical fit and do not account for the required patient-specific biomechanical support. Three-dimensional (3D) scanning and manufacturing technologies allow manufacturing PD-AFOs customized for the patient’s anatomy and functional needs. This paper aimed to report the overall procedure for designing and manufacturing a novel, fiberglass-reinforced polyamide, custom PD-AFO. The feasibility of the proposed procedure was tested in a case study. The methodology can be divided into the following steps: (i) foot and leg scanning, (ii) 3D design, and (iii) additive manufacturing via selective laser sintering. A custom PD-AFO was designed and manufactured for a 67-year-old male drop-foot patient following paraparesis in severe discarthrosis after spine stabilization surgery. AFO mechanical properties were measured via an ad hoc setup based on a servohydraulic testing machine. The functional outcome was assessed via gait analysis in three conditions: shod (no AFO), wearing an off-the-shelf PD-AFO, and wearing the patient-specific PD-AFO. As expected, wearing the PD-AFO resulted in increased ankle dorsiflexion in the swing phase with respect to the shod condition. Sagittal rotations of the hip, knee, and ankle joints were similar across PD-AFO conditions, but the custom PD-AFO resulted in faster walking speed with respect to the off-the-shelf (walking speed: 0.91 m/s versus 0.85 m/s). Additionally, the patient scored the custom PD-AFO as more comfortable (VAS score: 9.7 vs. 7.3). While the present analysis should be extended to a larger cohort of drop-foot patients, the novel PD-AFO seems to offer a valid, custom solution for drop-foot patients not satisfied with standard orthotics. Full article

Background and Objectives: Ankle foot orthoses (AFOs) are commonly used by stroke patients to walk safely and efficiently. Both posterior AFOs (PAFOs) and anterior AFOs (AAFOs) are available. The objective of this study was to compare the efficacy of AAFOs and PAFOs in the treatment of ankle spasticity. Materials and Methods: A crossover design with randomization for the interventions and blinded assessors was used. Twenty patients with chronic stroke, a Modified Ashworth Scale (MAS) score of the ankle joint of 2, and a Tardieu angle ≥20 degrees were recruited. The patients were assigned to wear either an AAFO or PAFO at random and subsequently crossover to the other AFO. Results: Twenty stroke patients with ankle spasticity were recruited. The mean age was 46.60 (38–60) years. The mean time since stroke onset was 9.35 (6–15) months. It was discovered that the AAFO improved walking speed as well as the stretch reflex dynamic electromyography (dEMG) and walking dEMG amplitudes of the medial gastrocnemius muscles more significantly than the PAFO (p < 0.05). Conclusions: The AAFO had greater efficacy in reducing both static and dynamic ankle spasticity, and allowed for faster walking than the PAFO. The stretch reflex and walking dEMG amplitudes could be used for quantitative spasticity assessment. Full article

Background: Cerebral palsy (CP) is the most common cause of motor disability in children and can cause severe gait deviations. The sagittal gait patterns classification for children with bilateral CP is an important guideline for the planning of the rehabilitation process. Ankle foot orthoses should improve the biomechanical parameters of pathological gait in the sagittal plane. Methods: A systematic search of the literature was conducted to identify randomized controlled trials (RCT) and controlled clinical trials (CCT) which measured the effect of ankle foot orthoses (AFO) on the gait of children with spastic bilateral CP, with kinetic, kinematic, and functional outcomes. Five databases (Pubmed, Scopus, ISI Web of SCIENCE, SciELO, and Cochrane Library) were searched before February 2020. The PEDro Score was used to assess the methodological quality of the selected studies and alignment with the Cochrane approach was also reviewed. Prospero registration number: CRD42018102670. Results: We included 10 studies considering a total of 285 children with spastic bilateral CP. None of the studies had a PEDro score below 4/10, including five RCTs. We identified five different types of AFO (solid; dynamic; hinged; ground reaction; posterior leaf spring) used across all studies. Only two studies referred to a classification for gait patterns. Across the different outcomes, significant differences were found in walking speed, stride length and cadence, range of motion, ground force reaction and joint moments, as well as functional scores, while wearing AFO. Conclusions: Overall, the use of AFO in children with spastic bilateral CP minimizes the impact of pathological gait, consistently improving some kinematic, kinetic, and spatial-temporal parameters, and making their gait closer to that of typically developing children. Creating a standardized protocol for future studies involving AFO would facilitate the reporting of new scientific data and help clinicians use their clinical reasoning skills to recommend the best AFO for their patients. Full article

The ankle joint of a powered ankle–foot orthosis (PAFO) is a prominent component, as it must withstand the dynamic loading conditions during its service time, while delivering all the functional requirements such as reducing the metabolic effort during walking, minimizing the stress on the user’s joint, and improving the gait stability of the impaired subjects. More often, the life of an AFO is limited by the performance of its joint; hence, a careful design consideration and material selection are required to increase the AFO’s service life. In the present work, a compact AFO joint was designed based on a worm gear mechanism with steel and brass counterparts due to the fact of its large torque transfer capability in a single stage, enabling a compact joint. Further, it provided an added advantage of self-locking due to the large friction that prevents backdrive, which is beneficial for drop-foot recovery. The design was verified using nonlinear finite element analysis for maximum torque situations at the ankle joint during normal walking. The results indicate stress levels within its design performance; however, it is recommended to select high-grade structural steel for the ankle shaft as the highest stresses in AFO were located on it. Full article

The aim of this study was to investigate the immediate static balance effects of bare foot, UD-Flex ankle–foot orthosis (AFO), and AFO using wire (AOW) of patients with stroke with foot drop. Seventeen patients with stroke with foot drop (8 men and 9 women) were randomized to three conditions (bare foot, UD-Flex AFO, or AOW made with a flexible material). Static balance was assessed using the Zebris (Zebris GmbH, Isny, Germany) and BioRescue (RM Ingenierie, Rodez, France) pressure platform by a single examiner, who did not design the AOW. The order of testing with the equipment was random. The center of pressure path length (mm) measured using Zebris showed significant differences among the three conditions (bare foot, 484.47 ± 208.42; UD-Flex AFO, 414.59 ± 144.43; AOW, 318.29 ± 157.60) (p < 0.05). The bare-foot condition was not significantly different from the UD-Flex AFO condition (p > 0.05), but was significantly different from the AOW condition (p < 0.05). The surface area ellipse (mm²) measured using BioRescue showed significant differences among the three conditions (bare foot, 241.35 ± 153.76; UD-Flex AFO, 277.41 ± 381.83; AOW, 68.06 ± 48.98) (p < 0.05). The bare-foot condition was not significantly different from the UD-Flex AFO condition (p > 0.05), but the AOW condition was significantly different from the bare-foot (p < 0.05) and from the UD-Flex AFO conditions (p < 0.05). We suggest using the AOW made of flexible materials and wire instead of the UD-Flex AFO to improve immediate static balance of patients with stroke with foot drop after stroke. Further studies on the effects of dynamic balance and gait are required. Full article