Ankle Rehabilitation Research Articles

A novel ankle rehabilitation device based on a reconfigurable 3-RPS parallel manipulator

This paper deals with the constraint-based design, optimum design and reconfiguration strategy of a 3-RPS parallel manipulator. Some design conditions related to the base and moving-platform design parameters and the three degree-of-freedom operation modes are derived. A 3-RPS parallel manipulator with two types of operation modes is generated by following those conditions. Due to its potential advantages, this manipulator is used as an ankle rehabilitation device which can cover the ankle joint motion. To derive the optimum parameters, kinematic optimization is conducted by initially parametrizing the orientation workspace and it turns out that its orientation workspace is not symmetrical. The singularity loci are traced in its orientation workspace. A performance index, named Maximum Inscribed Circle Diameter (MICD) is presented to assess the maximum tilt of the moving-platform for any azimuth angle. The distributions of MICD are plotted in the design space for different moving-platform heights. The optimum region with regard to MICD is obtained. It is noteworthy that the evolution of MICD as a function of moving-platform height in both operation modes is the opposite. Therefore, a reconfiguration strategy is proposed to ensure the moving-platform working above the minimum required orientation for any moving-platform height.

Technology-Assisted Ankle Rehabilitation Improves Balance and Gait Performance in Stroke Survivors: A Randomized Controlled Study With 1-Month Follow-Up.

Many stroke survivors have limited ankle range of motion (ROM) caused by weak dorsiflexors and stiff plantarflexors. Passive ankle stretching exercises with physical therapists or a stretching board are usually recommended, but these treatments have some limitations (e.g., cost and availability of physical therapists). In this paper, we assessed the results of ankle stretching exercises delivered by a robotic ankle stretching system called motorized ankle stretcher (MAS) that we developed or by a stretching board on ankle ROM, balance control, and gait performance. The 16 stroke survivors were randomly assigned to an intervention group (IG) or a control group (CG) and participated in seven sessions of dorsiflexion stretching exercises for three-and-a-half consecutive weeks. Laboratory assessments included pre-assessment (baseline at the beginning of the first exercise session), post-assessment (at the end of the seventh exercise session), and retention assessment (one month after the seventh exercise session). All assessments included ankle ROM for the affected side, static/dynamic balance control with a sensory organization test (SOT), walking speed, walking cadence, and step length for the affected and unaffected sides. During seven sessions of ankle stretching exercises, the IG performed them using the MAS, and the CG used a stretching board. The IG significantly improved ankle ROM, SOT scores (i.e., static/dynamic balance control), walking speeds, walking cadences, and step lengths for the unaffected side after completing the seven exercise sessions of ankle stretching exercises and maintained the enhancements at the retention assessment. The CG did not significantly improve across the majority of outcome measures except for the SOT scores between the pre-assessment and retention assessment. Future work will investigate the ideal intensity, frequency, and duration of exercising with the MAS. Our research on technology-assisted ankle rehabilitation, which can ascertain the level of persistent improvement, long-term performance retention, and carry-over effects in stroke survivors, can be used to inform future designs.

Compliant mechanism for ankle rehabilitation device. Part II: optimization and simulation results

As rehabilitation robotics become more popular, a great amount of research is focused on safety measures. In the design of an ankle rehabilitation device multiple safety techniques must be embedded. A solution is represented by a compliant mechanism that could take the overload from the motor, in case of emergency, and not further damage the patient’s foot. In this paper two designs of compliant mechanisms are studied with the help of finite element analysis, providing two solutions of elastic elements.

Compliant mechanism for ankle rehabilitation device; Part I: modelling and design

Robotic rehabilitation devices are able to meet certain requirements for long time rehabilitation, such as compact design, repeatability and storage patients’ evolution. As ankle injuries have a high incidence among the population, regardless of their age or activity, the need for an easy to manufacture rehabilitation device emerges. The proposed design offers two degrees of freedom, required for a full recovery of the ankle joint and programmable exercises. Although a safety button can be included in the electronic system that can be operated by the patient, extra safety measures are required in order not to damage furthermore the rehabilitated limb. A compliant mechanism that can bear the extra load from the motors’ crank, in case of overloading of the joint, is required. In this paper some design requirements and systematic synthesis methods for a compliant mechanism are presented.

Foot-Mounted Inertial Measurement Units-Based Device for Ankle Rehabilitation

Ankle sprains are frequent injuries that occur among people of all ages. Ankle sprains constitute approximately 15% of all sports injuries, and are the most common traumatic emergencies. Without proper treatment and rehabilitation, a more severe sprain can weaken the ankle, making it more likely for new injures, and leading to long-term problems. In this work, we present an inertial measurement units (IMU)-based physical interface for measuring the foot attitude, and a graphical user interface that acts as a visual guide for patient rehabilitation. A foot-mounted physical interface for ankle rehabilitation was developed. The physical interface is connected to the computer by a Bluetooth link, and provides feedback to the patient while performing dorsiflexion, plantarflexion, eversion, and inversion exercises. The system allows for in-home rehabilitation at an affordable price while engaging the patient through active therapy. According to the results, more consistent rehabilitation could be achieved by providing feedback on foot angular position during therapy procedures.

Individuals with recurrent ankle sprain demonstrate postural instability and neuromuscular control deficits in unaffected side

To compare proprioception, postural stability, and neuromuscular control between patients with mechanical laxity and recurrent ankle sprain. Among 86 patients with ankle instability, 45 patients had mechanical laxity (mean age 27.2 ± 7.0years) and 41 had recurrent ankle sprain (mean age 25.1 ± 9.2years). Both the affected and unaffected ankles of each patient were evaluated. Proprioception and neuromuscular control tests were conducted using an isokinetic machine, and postural stability was tested using a postural stabilometry system. Proprioception was not significantly different between the unaffected or affected ankles of the mechanical laxity group compared with those of the recurrent ankle sprain group (n.s). Static and dynamic postural stability and neuromuscular control were similar in the affected ankles between the two groups (n.s). However, postural stability (static, overall: p = 0.009, anterior-posterior: p = 0.028, medial-lateral: p = 0.022; dynamic, overall: p = 0.012, anterior-posterior: p = 0.004, medial-lateral: p = 0.001) and neuromuscular control (inversion: p = 0.031, eversion: p = 0.039, dorsiflexion: p = 0.029, plantarflexion: p = 0.035) were significantly decreased in the unaffected ankles of the recurrent ankle sprain group compared with those of the mechanical laxity group. The unaffected ankles of the recurrent ankle sprain group showed significant decreases in both postural stability and neuromuscular control compared with the mechanical laxity group. Clinicians and therapists should consider unaffected ankle rehabilitation in patients with recurrent ankle sprain to prevent future sprain events. Case-control study, III.

The effect of sensory-targeted ankle rehabilitation strategies on single-leg center of pressure elements in those with chronic ankle instability: A randomized clinical trial

ObjectivesTo determine the effects of sensory-targeted ankle rehabilitation strategies on laboratory-oriented measures of single-leg balance in those with chronic ankle instability. DesignNon-inferiority randomized controlled trial. MethodsSeventy-seven participants with self-reported chronic ankle instability were randomized into 4 treatment groups: Ankle joint mobilization, plantar massage, triceps surae stretching, and a control group. All participants performed 3 trials of single-leg balance on a force plate with eyes open and closed at 3 time points (baseline, immediately after the first treatment, and following 6 treatments over 2 weeks). The spatial (standard deviation), temporal (velocity), and spatiotemporal (time-to-boundary) elements of center of pressure excursions in single-leg balance were evaluated with eyes open and eyes closed at each time point. Immediate and final change scores were calculated for each group from the baseline values on these variables. ResultsJoint mobilization produced immediate improvements in the temporal elements with eyes open and closed that exceeded the minimum detectable changes for these measures. Plantar massage and triceps surae stretching also enhanced the temporal element after a single treatment, but only with eyes closed. No substantial benefit of any of the interventions were found after 2-weeks of treatment, regardless of treatment group. ConclusionsSensory-targeted ankle rehabilitation strategies substantially improve single-leg postural control after one treatment, but these changes are short-lived. Future research is needed to determine whether combinations of sensory-targeted ankle rehabilitation strategies with other therapeutic interventions potentially improve single-leg balance stability in those with CAI compared to use in isolation. Clinical trial registration numberNCT01541657.

Screw theory based mathematical modeling and kinematic analysis of a novel ankle rehabilitation robot with a constrained 3-PSP mechanism topology

As a common athletics injury in orthopedics clinic, ankle injury may affect a person’s daily life and ankle injury rehabilitation has gained increasing interests from the medical and robotic societies. A novel hybrid ankle rehabilitation robot is proposed, which composing of a serial and a parallel part. In order to analyze its kinematic performances, the parallel part of the robot is simplified as a constrained 3-PSP parallel mechanism. A mathematical model for the parallel part of the robot is established based on the screw theory. Then the inverse kinematics is obtained, and the reciprocal twists, Jacobian matrices and the singularity of the robot are analyzed. Finally the workspace of the central point on the moving platform is predicted. The kinematic analyses manifest that the proposed hybrid rehabilitation robot not only can realize three kinds of ankle rehabilitation motions, but also can eliminate singularity with enhanced workspace. The workspace of the central point reveals that the hybrid robot can fully meet the demanded rehabilitation space by comparing with the clinic demands. Our results reveals the characteristic structure of the hybrid rehabilitation robot and its superiority, it offers some basis data for the future enhancement of the device.

Early motion and directed exercise (EMADE) versus usual care post ankle fracture fixation: study protocol for a pragmatic randomised controlled trial

BackgroundFollowing surgical fixation of ankle fractures, the traditional management has included immobilisation for 6 weeks in a below-knee cast. However, this can lead to disuse atrophy of the affected leg and joint stiffness. While early rehabilitation from 2 weeks post surgery is viewed as safe, controversy remains regarding its benefits. We will compare the effectiveness of early motion and directed exercise (EMADE) ankle rehabilitation, against usual care, i.e. 6 weeks’ immobilisation in a below-knee cast.Method/designWe have designed a pragmatic randomised controlled trial (p-RCT) to compare the EMADE intervention against usual care. We will recruit 144 independently living adult participants, absent of tissue-healing comorbidities, who have undergone surgical stabilisation of isolated Weber B ankle fractures. The EMADE intervention consists of a non-weight-bearing progressive home exercise programme, complemented with manual therapy and education. Usual care consists of immobilisation in a non-weight-bearing below-knee cast. The intervention period is between week 2 and week 6 post surgery. The primary outcome is the Olerud and Molander Ankle Score (OMAS) patient-reported outcome measure (PROM) at 12 weeks post surgery. Secondary PROMs include the EQ-5D-5 L questionnaire, return to work and return to driving, with objective outcomes including ankle range of motion. Analysis will be on an intention-to-treat basis. An economic evaluation will be included.DiscussionThe EMADE intervention is a package of care designed to address the detrimental effects of disuse atrophy and joint stiffness. An advantage of the OMAS is the potential of meta-analysis with other designs. Within the economic evaluation, the cost-utility analysis, may be used by commissioners, while the use of patient-relevant outcomes, such as return to work and driving, will ensure that the study remains pertinent to patients and their families. As it is being conducted in the clinical environment, this p-RCT has high external validity. Accordingly, if significant clinical benefits and cost-effectiveness are demonstrated, EMADE should become a worthwhile treatment option. A larger-scale, multicentre trial may be required to influence national guidelines.Trial registrationISRCTN, ID: ISRCTN11212729. Registered retrospectively on 20 March 2017.

Designing and implementing a plug-in type repetitive controller for a redundantly actuated ankle rehabilitation robot

This article is focused on increasing the tracking performance of a developed ankle rehabilitation robot subject to external disturbance. A plug-in-type repetitive controller cascaded to a proportional–integral–derivative controller is designed and implemented in order to make improvement in the tracking ability of the parallel mechanism while performing the common range of motion exercises which are intensive training exercises in ankle rehabilitation. First, the trajectory tracking control is simply implemented by the PID controllers, the parameters of which are optimally tuned using Cuckoo search algorithm. Then, the designed RC is plugged into the system and trajectory tracking control is carried out. Performance measurements of the PID controller and plug-in RC controller are estimated using error-based performance methods and considerable improvements are observed in attenuating the external disturbance and decreasing the tracking error when the plug-in RC is implemented.

Adaptive Patient-Cooperative Control of a Compliant Ankle Rehabilitation Robot (CARR) With Enhanced Training Safety

This paper proposes a new adaptive patient-cooperative control strategy for improving the effectiveness and safety of robot-assisted ankle rehabilitation. This control strategy has been developed and implemented on a compliant ankle rehabilitation robot (CARR). The CARR is actuated by four Festo Fluidic muscles located to the calf in parallel, has three rotational degrees of freedom. The control scheme consists of a position controller implemented in joint space and a high-level admittance controller in task space. The admittance controller adaptively modifies the predefined trajectory based on real-time ankle measurement, which enhances the training safety of the robot. Experiments were carried out using different modes to validate the proposed control strategy on the CARR. Three training modes include: 1) a passive mode using a joint-space position controller, 2) a patient–robot cooperative mode using a fixed-parameter admittance controller, and 3) a cooperative mode using a variable-parameter admittance controller. Results demonstrate satisfactory trajectory tracking accuracy, even when externally disturbed, with a maximum normalized root mean square deviation less than 5.4%. These experimental findings suggest the potential of this new patient-cooperative control strategy as a safe and engaging control solution for rehabilitation robots.

Development Of A Wearable Ankle Rehabilitation Device For Patient With Calf Muscles Flexibility Problems

This paper presents the development process and analysis of a wearable ankle rehabilitation device designed for patient with calf muscles flexibility problems. The device is used to help patient in exercising the ankle to strengthen, lengthen and maintain the calf muscles. By using a joystick module to control the actuation of the servo motor, the ankle brace moves the ankle to plantar flexion and dorsiflexion movements. Besides that, MyoWareTM Muscle Sensor is used to generate electromyography (EMG) signal from the calf muscles to monitor the servo motor. Exercising the ankle frequently can increase the calf muscles flexibility. The robotic ankle brace device accommodates the robot-guided at-home therapy requirements and is user-friendly. This allowed patient to perform exercise on the ankle more frequent and the recovery process can be reduced effectively. Other than being used as a treatment, this ankle brace is suitable for daily exercise too. Keywords: rehabilitation; electromyography; servo-motor; control systems

Towards Optimal Platform-Based Robot Design for Ankle Rehabilitation: The State of the Art and Future Prospects.

This review aims to compare existing robot-assisted ankle rehabilitation techniques in terms of robot design. Included studies mainly consist of selected papers in two published reviews involving a variety of robot-assisted ankle rehabilitation techniques. A free search was also made in Google Scholar and Scopus by using keywords “ankle∗,” and “robot∗,” and (“rehabilitat∗” or “treat∗”). The search is limited to English-language articles published between January 1980 and September 2016. Results show that existing robot-assisted ankle rehabilitation techniques can be classified into wearable exoskeleton and platform-based devices. Platform-based devices are mostly developed for the treatment of a variety of ankle musculoskeletal and neurological injuries, while wearable ones focus more on ankle-related gait training. In terms of robot design, comparative analysis indicates that an ideal ankle rehabilitation robot should have aligned rotation center as the ankle joint, appropriate workspace, and actuation torque, no matter how many degrees of freedom (DOFs) it has. Single-DOF ankle robots are mostly developed for specific applications, while multi-DOF devices are more suitable for comprehensive ankle rehabilitation exercises. Other factors including posture adjustability and sensing functions should also be considered to promote related clinical applications. An ankle rehabilitation robot with reconfigurability to maximize its functions will be a new research point towards optimal design, especially on parallel mechanisms.

Development of a New Robotic Ankle Rehabilitation Platform for Hemiplegic Patients after Stroke

A large amount of hemiplegic survivors are suffering from motor impairment. Ankle rehabilitation exercises act an important role in recovering patients' walking ability after stroke. Currently, patients mainly perform ankle exercise to reobtain range of motion (ROM) and strength of the ankle joint under a therapist's assistance by manual operation. However, therapists suffer from high work intensity, and most of the existed rehabilitation devices focus on ankle functional training and ignore the importance of neurological rehabilitation in the early hemiplegic stage. In this paper, a new robotic ankle rehabilitation platform (RARP) is proposed to assist patients in executing ankle exercise. The robotic platform consists of two three-DOF symmetric layer-stacking mechanisms, which can execute ankle internal/external rotation, dorsiflexion/plantarflexion, and inversion/eversion exercise while the rotation center of the distal zone of the robotic platform always coincides with patients' ankle pivot center. Three exercise modes including constant-speed exercise, constant torque-impedance exercise, and awareness exercise are developed to execute ankle training corresponding to different rehabilitation stages. Experiments corresponding to these three ankle exercise modes are performed, the result demonstrated that the RARP is capable of executing ankle rehabilitation, and the novel awareness exercise mode motivates patients to proactively participate in ankle training.

Path-planning of a hybrid parallel robot using stiffness and workspace for foot rehabilitation

Stiffness is one of the important parameters for estimating the performance of hybrid parallel robots as it is not constant throughout its workspace. The aim of this study is to provide an optimum path based on maximum stiffness within the workspace of a 9-degree-of-freedom hybrid parallel mechanism configuration, which includes nine linear actuators connecting one stationary and two moving platforms in series. The proposed robot is designed for ankle rehabilitation, where accurate and precise movement of lower extremities is required. The design takes advantage of two important characteristics of parallel robots: stiffness and workspace. The proposed methodology to determine the stiffness of hybrid robot in three single axes is based on calculation of position vector of each actuator in any particular pose, by considering the inverse kinematics of the system, in order to obtain the magnitude and direction of the applied forces. The results obtained from the workspace calculations have been compared with those of two standard parallel mechanisms including a 6-degree-of-freedom hexapod and a tripod with 3 degrees of freedom. The stiffness of the robot has been calculated in simulation and then compared with those of a developed prototype hybrid model in two different case studies.

Construct and control of feet gait mechanisms for walking training

Gait training or gait rehabilitation is one of the major physiotherapy for stroke patients. Evidently, the robot-assisted gait training, as one part of medical technology innovation breakthrough, has important role in the rehabilitation process. The robot effectively improves treatment outcomes, fast recovery time and better convenience from traditional treatment. Typically, stroke patients are trained to walk on treadmill while a physiotherapist carefully supports and re-correct the gait pattern of the patient. For repetitive and long-time rehabilitation, it is so difficult that the physiotherapist can maintain the quality of treatment consistently. To solve such difficulties, the robotic platform is proposed for automatic guiding the gait pattern for ankle rehabilitation. The robot consists of left and right sides. Each of them is actuated by two linear and one rotational actuator. PID algorithm is implemented for position control of each joint. The experimental results show the tracking error in non-loaded and loaded cases.

Nutation Motion Based Trajectory Planning for a Novel Hybrid Ankle Rehabilitation Device

Nutation Motion Based Trajectory Planning for a Novel Hybrid Ankle Rehabilitation Device

Ankle passive and active movement training in children with acute brain injury using a wearable robot.

To evaluate the feasibility and effectiveness of a wearable robotic device in guiding isometric torque generation and passive-active movement training for ankle motor recovery in children with acute brain injury. Ten inpatient children with acute brain injury being treated in a rehabilitation hospital. Daily robot-guided ankle passive-active movement therapy for 15 sessions, including isometric torque generation under real-time feedback, stretch-ing, and active movement training with motivating games using a wearable ankle rehabilitation robot. Ankle biomechanical improvements induced by each training session including ankle range of motion (ROM), muscle strength, and clinical (Fugl-Meyer Lower-Extremity (FMLE), Pediatric Balance Scale (PBS)) and biomechanical (ankle ROM and muscle strength) outcomes over 15 training sessions. As training progressed, improvements in biomechanical performance measures followed logarithmic curves. Each training session increased median dorsiflexion active range of motion (AROM) 2.73° (standard deviation (SD) 1.14), dorsiflexion strength 0.87 Nm (SD 0.90), and plantarflexion strength 0.60 Nm (SD 1.19). After 15 training sessions the median FMLE score had increased from 14.0 (SD 10.11) to 23.0 (SD 11.4), PBS had increased from 33.0 (SD 19.99) to 50.0 (SD 23.13) (p < 0.05), median dorsiflexion and plantarflexion strength had improved from 0.21 Nm (SD 4.45) to 4.0 Nm (SD 7.63) and 8.33 Nm (SD 10.18) to 18.45 Nm (SD 14.41), respectively, median dorsiflexion AROM had improved from -10.45° (SD 12.01) to 11.87° (SD 20.69), and median dorsiflexion PROM increased from 20.0° (SD 9.04) to 25.0° (SD 8.03). Isometric torque generation with real-time feedback, stretching and active movement training helped promote neuroplasticity and improve motor performance in children with acute brain injury.

Reviewing Clinical Effectiveness of Active Training Strategies of Platform-Based Ankle Rehabilitation Robots.

Objective This review aims to provide a systematical investigation of clinical effectiveness of active training strategies applied in platform-based ankle robots. Method English-language studies published from Jan 1980 to Aug 2017 were searched from four databases using key words of “Ankle∗” AND “Robot∗” AND “Effect∗ OR Improv∗ OR Increas∗.” Following an initial screening, three rounds of discrimination were successively conducted based on the title, the abstract, and the full paper. Result A total of 21 studies were selected with 311 patients involved; of them, 13 studies applied a single group while another eight studies used different groups for comparison to verify the therapeutic effect. Virtual-reality (VR) game training was applied in 19 studies, while two studies used proprioceptive neuromuscular facilitation (PNF) training. Conclusion Active training techniques delivered by platform ankle rehabilitation robots have been demonstrated with great potential for clinical applications. Training strategies are mostly combined with one another by considering rehabilitation schemes and motion ability of ankle joints. VR game environment has been commonly used with active ankle training. Bioelectrical signals integrated with VR game training can implement intelligent identification of movement intention and assessment. These further provide the foundation for advanced interactive training strategies that can lead to enhanced training safety and confidence for patients and better treatment efficacy.

Disturbance-Estimated Adaptive Backstepping Sliding Mode Control of a Pneumatic Muscles-Driven Ankle Rehabilitation Robot.

A rehabilitation robot plays an important role in relieving the therapists’ burden and helping patients with ankle injuries to perform more accurate and effective rehabilitation training. However, a majority of current ankle rehabilitation robots are rigid and have drawbacks in terms of complex structure, poor flexibility and lack of safety. Taking advantages of pneumatic muscles’ good flexibility and light weight, we developed a novel two degrees of freedom (2-DOF) parallel compliant ankle rehabilitation robot actuated by pneumatic muscles (PMs). To solve the PM’s nonlinear characteristics during operation and to tackle the human-robot uncertainties in rehabilitation, an adaptive backstepping sliding mode control (ABS-SMC) method is proposed in this paper. The human-robot external disturbance can be estimated by an observer, who is then used to adjust the robot output to accommodate external changes. The system stability is guaranteed by the Lyapunov stability theorem. Experimental results on the compliant ankle rehabilitation robot show that the proposed ABS-SMC is able to estimate the external disturbance online and adjust the control output in real time during operation, resulting in a higher trajectory tracking accuracy and better response performance especially in dynamic conditions.