A survey on foot drop and functional electrical stimulation

Koopman-Based Model Predictive Control of Functional Electrical Stimulation for Ankle Dorsiflexion and Plantarflexion Assistance

Functional Electrical Stimulation (FES) can be an effective tool to augment paretic muscle function and restore normal ankle function. Our approach incorporates a real-time, data-driven Model Predictive Control (MPC) scheme built upon a Koopman operator theory (KOT) framework. This framework adeptly captures the complex nonlinear dynamics of ankle motion in a linearized form, enabling the application of linear control approaches for highly nonlinear FES-actuated dynamics. Our method accurately predicts the FES-induced ankle movements, accounting for nonlinear muscle actuation dynamics, including the muscle activation for both plantarflexors and dorsiflexors (Tibialis Anterior (TA)). The linear prediction model derived through KOT allowed the formulation of the MPC problem with linear state space dynamics, enhancing the FES-driven control's real-time feasibility, precision, and adaptability. We demonstrate the effectiveness and applicability of our approach through comprehensive simulations and experimental trials, including three participants with no disability and a participant with Multiple Sclerosis. Our findings highlight the potential of a KOT-based MPC approach for FES-based gait assistance that offers effective and personalized assistance for individuals with gait impairment conditions.

Postoperative Foot Drop After Spinal Surgery: Etiology, Presentation, and Management Strategies

» The incidence of postoperative foot drop after spine surgery is estimated at 3.33%, with higher rates reported in complex procedures such as high-grade spondylolisthesis correction (up to 30%). Risk factors include disc-space distraction, deformity corrections, prolonged surgery, and advanced patient age.» The primary mechanisms of postoperative foot drop include direct nerve trauma, stretch injuries from retraction or distraction, compression from hematomas or implants, and ischemic damage because of disrupted blood flow.» Preoperative counseling, intraoperative precision, appropriate disc space distraction, and careful nerve retraction are key to mitigating the risk of foot drop, with ongoing research needed to standardize preventive and management guidelines.» Treatment strategies are tailored to the underlying cause, ranging from conservative options (physical therapy, ankle-foot orthoses, and functional electrical stimulation) to surgical interventions (hematoma evacuation, implant removal, neurolysis, nerve transfer, and tendon transfer), although outcomes are highly variable.

Comprehensive Rehabilitation of a Patient With Foot Drop Secondary to Lumbar Canal Stenosis: A Case Report

One of the most prevalent degenerative musculoskeletal conditions is lumbar spinal canal stenosis (LSS), which is characterized by narrowing of the lumbar spinal canal that pressures the nerve roots and cauda equine. LSS, when treated surgically, usually presents with foot drop as its major complication. Foot drop is a common presentation of several clinical diseases, traditionally characterized as severe weakening of ankle and toe dorsiflexion. Foot drop has a great impact on patients' lives, lowering their quality of life and affecting their activities of daily living. Ankle dorsiflexion weakness leads to foot drop and a high-stepping gait, which can cause multiple falls and accidents. This case study aimed to assess the efficacy of a customized physiotherapy program in a 50-year-old woman with paraparesis along with left foot drop and post-surgery complications following lumbar decompression and spinal fusion at L3-S1 (lumbar-sacral) level after a jerk experienced by her while working out in the gym. The objective was to determine the impact of individualized exercises on the patient's strength, gait, balance, and pelvic floor function over a 12-week rehabilitation period. The interventions included lower limb exercises (stretching exercises, strengthening exercises, and weight-bearing exercises), pelvic floor exercises, and core stability training. The findings demonstrated significant improvements in the patient's functional outcomes, as evidenced by enhanced scores in the Berg Balance Scale, Manual Muscle Testing, Dynamic Gait Index, Barthel Index, and Stanmore Assessment Questionnaire. Notable progress was observed in the strength, balance, gait, and pelvic floor function, highlighting the positive influence of targeted physiotherapeutic interventions. This case underscores the importance of tailored exercise plans in addressing the complexities of post-surgery challenges, emphasizing the potential for comprehensive recovery and improved overall quality of life through personalized physiotherapy.

A hybrid orthosis combining functional electrical stimulation and soft robotics for improved assistance of drop-foot

Drop-foot is characterised by an inability to lift the foot, and affects an estimated 3 million people worldwide. Current treatment methods include rigid splints, electromechanical systems, and functional electrical stimulation (FES). However, these all have limitations, with electromechanical systems being bulky and FES leading to muscle fatigue. This paper addresses the limitations with current treatments by developing a novel orthosis combining FES with a pneumatic artificial muscle (PAM). It is the first system to combine FES and soft robotics for application to the lower limb, as well as the first to employ a model of their interaction within the control scheme. The system embeds a hybrid controller based on model predictive control (MPC), which combines FES and PAM components to optimally balance gait cycle tracking, fatigue reduction and pressure demands. Model parameters are found using a clinically feasible model identification procedure. Experimental evaluation using the system with three healthy subjects demonstrated a reduction in fatigue compared with the case of only using FES, which is supported by numerical simulation results.

Evaluating Acute Bilateral Foot Drop: A Case Report

We illustrate the case of an 84-year-old Caucasian female who presented with complaints of bilateral lower extremity weakness and ambulation difficulties complicated by a unilateral deep venous thrombosis. Physical examination on hospital admission revealed an acute onset of bilateral foot drop with pes cavus deformity. Bilateral foot drop has been associated with a more chronic presentation due to metabolic, neurologic, and musculoskeletal etiologies. Acute onset of bilateral foot drop has been poorly defined in the literature and is considered a rare pathologic phenomenon, requiring additional investigation into the underlying cause of the presentation. We hypothesize that a spinal cord compression at the T12-L1 level resulted in L5 nerve root compression, resulting in our patient's presentation. Definitive treatment has not been established for this condition; however, studies have been completed to evaluate surgical versus conservative approaches to help restore patients' ambulatory function. Our aim is to incorporate this case report into the limited current literature on acute bilateral foot drop as well as outline possible treatment methods to restore impaired functionality.

Polymeric Orthosis with Electromagnetic Stimulator Controlled by Mobile Application for Bone Fracture Healing: Evaluation of Design Concepts for Medical Use

Background: The occurrence of bone fractures is increasing worldwide, mainly due to the health problems that follow the aging population. The use of additive manufacturing and electrical stimulators can be applied for bioactive achievements in bone healing. However, such technologies are difficult to be transferred to medical practice. This work aims to develop an orthosis with a combined magnetic field (CFM) electrostimulator that demonstrates concepts and design aspects that facilitate its use in a real scenario. Methods: A 3D-printed orthosis made of two meshes was manufactured using PLA for outer mechanical stabilization mesh and TPU for inner fixation mesh to avoid mobilization. A CFM stimulator of reduced dimension controlled by a mobile application was coupled onto the orthosis. The design concepts were evaluated by health professionals and their resistance to chemical agents commonly used in daily activities were tested. Their thermal, chemical and electrical properties were also characterized. Results: No degradation was observed after exposure to chemical agents. The CMF achieved proper intensity (20-40 µT). The thermal analysis indicated its appropriate use for being modelled during clinical assessment. Conclusion: An orthosis with a coupled electrostimulator that works with a combined magnetic field and is controlled by mobile application was developed, and it has advantageous characteristics when compared to traditional techniques for application in real medical environments.

Early-Stage Physical Therapy for a Patient With Proximal Tibial Fracture With Acute Compartment Syndrome and Neurovascular Deficits Managed With External Fixation Complicated by Chronic Osteomyelitis: A Case Report

Tibial fractures occur following low-energy and high-energy trauma resulting from indirect and direct impacts, respectively. High-velocity trauma like road traffic accidents usually results in open fractures of the tibia associated with acute compartment syndrome, posing a serious threat. Thus, this injury requires prompt operative management with fasciotomy followed by fixating the fracture with an external fixator to avoid infection. Despite all the efforts, sometimes this condition may lead to osteomyelitis of the tibia requiring further care. Meanwhile, the patient has to be kept immobilized for a longer duration of time, which allows further complications to occur. Therefore, structured physiotherapeutic management of patients postoperatively is of immense necessity to prevent complications associated with prolonged immobility and achieve an optimal level of functional independence, thereby facilitating the patient to come back to near-normal life as soon as possible. Our case report provides a structured early-stage postoperative physical therapy treatment protocol for a patient with a proximal tibial fracture with acute compartment syndrome and neurovascular deficit managed with Ilizarov fixation.

Using Deep Learning to Predict Minimum Foot-Ground Clearance Event from Toe-Off Kinematics

Efficient, adaptive, locomotor function is critically important for maintaining our health and independence, but falls-related injuries when walking are a significant risk factor, particularly for more vulnerable populations such as older people and post-stroke individuals. Tripping is the leading cause of falls, and the swing-phase event Minimum Foot Clearance (MFC) is recognised as the key biomechanical determinant of tripping probability. MFC is defined as the minimum swing foot clearance, which is seen approximately mid-swing, and it is routinely measured in gait biomechanics laboratories using precise, high-speed, camera-based 3D motion capture systems. For practical intervention strategies designed to predict, and possibly assist, swing foot trajectory to prevent tripping, identification of the MFC event is essential; however, no technique is currently available to determine MFC timing in real-life settings outside the laboratory. One strategy has been to use wearable sensors, such as Inertial Measurement Units (IMUs), but these data are limited to primarily providing only tri-axial linear acceleration and angular velocity. The aim of this study was to develop Machine Learning (ML) algorithms to predict MFC timing based on the preceding toe-off gait event. The ML algorithms were trained using 13 young adults' foot trajectory data recorded from an Optotrak 3D motion capture system. A Deep Learning configuration was developed based on a Recurrent Neural Network with a Long Short-Term Memory (LSTM) architecture and Huber loss-functions to minimise MFC-timing prediction error. We succeeded in predicting MFC timing from toe-off characteristics with a mean absolute error of 0.07 s. Although further algorithm training using population-specific inputs are needed. The ML algorithms designed here can be used for real-time actuation of wearable active devices to increase foot clearance at critical MFC and reduce devastating tripping falls. Further developments in ML-guided actuation for active exoskeletons could prove highly effective in developing technologies to reduce tripping-related falls across a range of gait impaired populations.

Gait Biomechanics for Fall Prevention among Older Adults

In our currently ageing society, fall prevention is important for better healthy life expectancy and sustainable healthcare systems. While active outdoor walking is recommended as adequate exercise for the senior population, falls due to tripping and slipping exist as the primary causes of severe injuries. Minimum foot clearance (MFC) is the lowest vertical height of the foot during the mid-swing phase and indicates the risk of tripping. In contrast, coefficient of friction (COF) factors determine the occurrence of falls from slipping. Optimisation of the MFC and the COF for every step cycle prevents tripping and slipping, respectively. Even after the initiation of hazardous balance loss (i.e., tripping and slipping), falls can still be prevented as long as the requirements for balance are restored. Biomechanically, dynamic balance is defined by the bodily centre of mass and by the base of support: spatially—margin of stability and temporally—available response time. Fall prevention strategies should, therefore, target controlling the MFC, the COF and dynamic balance. Practical intervention strategies include footwear modification (i.e., shoe-insole geometry and slip-resistant outsoles), exercise (i.e., ankle dorsiflexors and core stabilisers) and technological rehabilitation (i.e., electrical stimulators and active exoskeletons). Biomechanical concepts can be practically applied to various everyday settings for fall prevention among the older population.

An evaluation of the reliability of the foot-tapping test in a healthy sample

The foot-tapping test (FTT) can be used to assess upper motor neuron dysfunction in clinical populations. However, relatively little is known regarding the reliability or normative values of the FTT in either healthy or clinical populations. Although several different FTT methods have been used, no study to date has demonstrated the reliability or validity of FTT by comparing it across several different counting methods in healthy persons. This unfortunately limits its usefulness in medicine and research.

OBJECTIVE

This study sought to examine the reliability and validity of the FTT in healthy individuals to determine its usefulness and to make recommendations for its implementation in clinical populations. Furthermore, the concurrent validity and reliability of using a force plate as an objective measure of foot-taps was considered.

DESIGN

Thirty-eight healthy individuals had their foot-tapping assessed using Live, Force Plate, and Video Counting methods over four separate visits.

METHODS

Participants were seated as per previous FTT recommendations and asked to tap their foot in 10-second intervals while the number of taps was counted via Live, Video, and Force Plate counters. This was done with both legs, with shoes ON and OFF, and repeated over four separate visits.

RESULTS

Despite significant differences between repeat trials for Force Plate and Video Counts (∼2 foot-taps, p < 0.01), test-retest reliability was high for all three methods (Pearson's R > 0.90). Dominant foot trials were higher (∼2 foot-taps, p < 0.05) than Non-dominant for all three counts. When performed with shoes ON, counts were higher (∼2 foot-taps, p < 0.05) than OFF for the Live and Force Plate counts. Reliability between visits was high (ICC > 0.80) and only the Video count was significantly lower for Visit 1 (p < 0.01).

CONCLUSIONS

Given findings, the authors suggest using a Force Plate counting method and have compiled a list of suggestions for future implementation of the FTT.