In-silico simulations to study the effects of ankle-joint misalignments in Ankle-Foot-Orthoses during level walking.

Exoskeletons and orthotic devices are commonly used in physical rehabilitation. However, these devices, fitting intimately with the human body, often lead to skin-related issues amongst users. Misalignments between orthotic and anatomical joints cause relative sliding motion between the limb and orthosis and also cause pressure points on the limb, which may contribute to these skin problems. This research quantifies the effects of sagittal plane ankle-joint misalignments for an ankle-foot orthosis (AFO) user during walking. A 2D mathematical model that simulates the effects of sagittal plane ankle-joint misalignments in terms of relative motion between the limb and the orthosis was developed using MATLAB software. The orthotic ankle-joint was systematically misaligned against the anatomical ankle-joint to generate various misalignment conditions. Published gait data of 5 healthy subjects was used to generate walking kinematics which was then superimposed with an articulated AFO. The simulations showed that Anterior-Posterior misalignments resulted in greater pistoning motion than Proximal-Distal misalignments. Combined misalignments (Posterior-Distal, Anterior-Proximal, Posterior-Proximal, and Anterior-Distal) resulted in higher overall relative motions between the limb and AFO. The model also predicted pressure points on the shank and foot caused by misalignments. This study demonstrates that misaligned ankle-joints in AFOs lead to relative sliding motion and pressure points during walking.

A biomechanical perspective on walking in patients with peripheral artery disease.

The most common symptom of peripheral artery disease (PAD) is intermittent claudication, which consists of debilitating leg pain during walking. In clinical settings, the presence of PAD is often noninvasively evaluated using the ankle-brachial index and imaging of the arterial supply. Furthermore, various questionnaires and functional tests are commonly used to measure the severity and negative effect of PAD on quality of life. However, these evaluations only provide information on vascular insufficiency and severity of the disease, but not regarding the complex mechanisms underlying walking impairments in patients with PAD. Biomechanical analyses using motion capture and ground reaction force measurements can provide insight into the underlying mechanisms to walking impairments in PAD. This review analyzes the application of biomechanics tools to identify gait impairments and their clinical implications on rehabilitation of patients with PAD. A total of 18 published journal articles focused on gait biomechanics in patients with PAD were studied. This narriative review shows that the gait of patients with PAD is impaired from the first steps that a patient takes and deteriorates further after the onset of claudication leg pain. These results point toward impaired muscle function across the ankle, knee, and hip joints during walking. Gait analysis helps understand the mechanisms operating in PAD and could also facilitate earlier diagnosis, better treatment, and slower progression of PAD.

A robust technique for optimal fitting of roll-over shapes of human locomotor systems.

The roll-over shape (ROS) effectively characterizes the lower limb's ability to roll forward during the single-limb support phase of human walking. ROS is modelled as an optimally fitted circular arc to the center of pressure (CoP) data transformed in the shank/leg-based local coordinate system. The commonly used method for optimal fitting of ROS is complex to implement and eliminates inherent individual variability in the ROS parameters during walking. We propose and validate a novel computerized method for optimal fitting of roll-over shapes of the lower limb during walking. Gait data of a healthy individual from Winter's book was used to generate ankle-foot and knee-ankle-foot roll-over shapes using the proposed method. The goodness of fit and form of both the roll-over shapes were validated with the literature. To test the robustness of the proposed technique, small random perturbations were introduced to the transformed CoP data and the effect of these small changes in the data on the ROS parameters was studied. The ROS parameters such as radius, arc length, subtended arc angle, and horizontal and vertical shift in the arc center did not change substantially with small changes in the CoP data. The proposed method is computationally efficient, and easy to implement for optimal fitting and characterization of ROS.

Considerations for Implementation of an Ankle-Foot Orthosis to Improve Mobility in Peripheral Artery Disease.

OBJECTIVE: To explore the perceptions of wearing an ankle-foot orthosis (AFO) in patients with peripheral artery disease (PAD) who did and did not adopt the AFO intervention. This follows a clinical trial of the effectiveness of an AFO in improving walking distances for patients with PAD-related claudication. DESIGN: A randomized crossover trial of standard of care and an AFO for 3 months. Semistructured interviews were conducted 1.5 months into the AFO intervention to understand acceptability, demand, implementation, and practicality. Data were analyzed using a summative content analysis approach. SETTING: Vascular surgery clinic and biomechanics research laboratory. PARTICIPANTS: Patients (N=15; male, 100%; age, 71.9±.6.7y; body mass index [calculated as weight in kilograms divided by height in meters squared], 29.0±.5.5; ankle brachial index: AFO intervention withdrawal, 0.543; AFO intervention completion, 0.740) with claudication completed the study, and 6 withdrew prior to intervention completion. INTERVENTIONS: A certified orthotist fit participants with an AFO that was worn for 3 months. MAIN OUTCOME MEASURES: Qualitative analysis of the semistructured interviews. RESULTS: Key differences were reported between AFO intervention completion and AFO intervention withdrawal. Six of 14 of AFO intervention completion participants described their initial reactions to the AFO as negative vs 3 of 6 AFO intervention withdrawal participants. Only 5 of 15 AFO intervention completion participants reported minimal use of the AFO compared with 5 of 6 AFO intervention withdrawal participants. The AFO intervention withdrawal group reported higher levels of physical discomfort with the use of the AFO (4/6 vs 7/15) and preexisting health issues becoming a barrier to the use of the AFO (3/6 vs 5/15). Positive aspects reported included ease in standing and walking for AFO intervention withdrawal (4/6) and AFO intervention completion groups (13/15) as well as walking straighter and longer with less pain for AFO intervention withdrawal (3/6) and AFO intervention completion groups (9/15). CONCLUSIONS: Patients withdrawing prior to completion of AFO intervention tended to have more negative perceptions, more comorbidities, and more physical discomfort than those completing the intervention. Both groups reported positive aspects of the AFO. Implementation studies are needed to address barriers to AFO adoption.

GRID: a model for the development of assistive devices in developing countries.

PURPOSE: An" Appropriate Assistive Device" is accessible, affordable and standardised in terms of quality and safety, and most importantly, has the functionality to satisfy the user needs. The cost of research and development (R&D) of such assistive products for a market that has limited purchasing power is a significant hurdle and traditional models of R&D may not work effectively in this case. This paper presents an experience-based viable model for the R&D of assistive devices for users in developing countries. METHOD: The model presented here has been evolved from the functioning of the TTK Centre for Rehabilitation Research and Device Development (R2D2) in IIT Madras, Chennai, India. The model is based on the four pillars of Grants-Research-Industry-Dissemination, hence the name GRID model. We have been effectively using this model involving academia, funding agencies, industry partners and users to develop appropriate assistive devices. Three case studies of assistive device development based on the GRID model are presented in this paper to elucidate practical implementation of the model. RESULTS: Using the GRID model, we have successfully accomplished the development of appropriate assistive devices and two of these devices will be launched in the coming months. CONCLUSIONS: The proposed GRID model is a viable model for the development of appropriate assistive devices in developing countries, and could likely be replicated in other parts of the world as well.IMPLICATIONS FOR REHABILITATIONThe GRID model is practically viable and provides a systematic approach for the development of high-quality, functional and affordable assistive devices.Implementation of the GRID model to develop assistive devices could attract more funding and committed stakeholders to this space, with the potential to change the assistive device landscape in developing countries by making available more functional and affordable devices.In effect, the model will benefit users of assistive devices by giving them a greater choice of available devices and empowering them to lead a quality life.

Identification and analysis of knee-ankle-foot orthosis design requirements based on a feedback survey of orthosis users in India.

PURPOSE: The world is advancing towards a technological revolution in various fields, yet the assistive devices available for people with disability, especially in developing countries, are in the most primitive stage. For many years, lower limb orthotics has been a neglected area of research and there is an urgent need to address the problems faced by lower limb orthosis users to enable them to lead an independent life. This work is a first step in this direction and aims to identify and analyse the needs of knee-ankle-foot orthosis (KAFO) users in India. METHOD: A structured feedback survey of 29 KAFO users was conducted at three rehabilitation centres located in South India. A feedback questionnaire and a novel outcome measure tool (trigger cards) were used as means to assess user satisfaction about their existing KAFOs. The results of the survey were analysed to obtain quantitative and qualitative outcomes. RESULTS: The survey identifies various biomechanical and functional issues associated with lower limb orthosis design. The results of the survey imply that there is an urgent need to solve issues, especially related to locked orthotic knee joint design. Additionally, it sheds light on the lifestyle and socio-economic issues of KAFO users that are likely prevalent in many other low- and middle-income countries. CONCLUSIONS: The outcomes of this survey can motivate and guide researchers to design improved orthotic solutions to meet the needs of lower limb orthosis users all over the world. Implications for Rehabilitation • This is a first of its kind survey that brings forth the needs of lower limb orthosis users in India, and is an important step towards rehabilitation and empowerment of people with lower limb disability. • The pilot survey helps to identify critical areas for design improvements in a knee-ankle-foot orthosis. • The outcomes of this survey can help researchers to design functionally improved assistive devices that better meet the needs of users than currently available technology in developing countries such as India.