Sujatha Srinivasan

The poorest populations in the world have the highest prevalence of lower limb disabilities, and lack of access to healthcare prevents many from lifting themselves out of poverty. This is particularly true for the large population of poliomyelitis-affected inhabitants of India, whose quality of life would benefit substantially from the provision of affordable, yet modern, dynamic knee-ankle-foot orthoses to assist in ambulation. To this end, this paper reports a study into the use of a low-cost, textile-based sensor interface for the myoelectric control of lower limb orthoses in restoring gait function. It reports experiments examining the accuracy with which gait events in the healthy limb (e.g., heel strike, toe-off) can be detected through the textile interface, with a view to triggering discrete control modes of a smart orthosis (i.e., knee lock and release) to support the atrophied limb during walking. Results show that prediction accuracy through the proposed interface (∼ 70%) approaches that of more traditional medical-grade sensors, despite its substantially lower cost.

Introduction The knee joint of a conventional knee-ankle-foot orthosis (KAFO) is locked during walking. This study aims to evaluate the effects of stance phase knee flexion on the kinematics, spatiotemporal parameters, and energy consumption of KAFO users. Materials and Methods A retrofitting drop lock that allows 12° of stance flexion in a single-axis knee joint was developed (called the semiflexion knee joint). Four subjects with quadriceps weakness volunteered to participate in the study. Gait analysis was conducted for the locked knee and the semiflexion knee orthosis using a calibrated eight-camera three-dimensional motion capture system. Preceding each trial, participants were given 5 days of gait training with the corresponding KAFO. Subjective feedback about the performance of the new KAFO was collected. Results Walking with the semiflexion KAFO did not significantly improve the speed (p = 0.161), cadence (p = 0.232), and stride length (p = 0.95) compared with walking with a locked KAFO. Although not significant (p = 0.132), trends of Physiological Cost Index (PCI) seemed to reduce in all subjects while walking with the semiflexion knee. Conclusions Using the KAFO with stance flexion did not significantly improve any of the locked knee gait parameters. However, there was a trend of reduction in the PCI score while walking with the semiflexion KAFO, and it also improved the ease of doing some activities of daily living.

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.

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 REHABILITATION The 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.

A Knee-Ankle-Foot orthosis (KAFO) is used as a supportive device by individuals with lower limb disability. A type of KAFO that allows knee flexion-extension is prescribed for people who need knee stability in the transverse and frontal planes. In such an orthosis, mimicking the human knee motion is vital to avoid relative motion (called pistoning) between the limb and the orthosis. A four-bar mechanism, owing to its polycentric nature, simplicity and ease of fabrication can provide a customizable, biomimetic solution. This paper presents an improved and robust optimization approach to synthesize a four-bar mechanism to closely mimic the anatomical knee motion. The reference human knee centrode is obtained from literature. A genetic algorithm is used for optimal synthesis of the fourbar mechanism. Results show that the average error between the reference centrode and the centrode of the synthesized four-bar mechanism is very small (0.2 mm). Thus, the synthesized crossed four-bar linkage can reproduce better anthropomorphic characteristics of the knee joint. The methodology can be used for the design of customized orthotic knee joints for KAFOs and knee braces.

Introduction Pistoning is relative sliding motion between an affected limb and its corresponding externally fit assistive device (like an orthosis). Pistoning causes skin problems, pain, and discomfort to the orthosis user. Misalignment of an orthotic joint with respect to the anatomical joint is one of the causes of pistoning motion, and the current knowledge pertaining to the effects of orthotic knee center (OKC) misalignments in lower-limb orthoses is limited. This work quantifies the effects of OKC misalignment in terms of relative motion between the limb and the orthosis and predicts locations of resultant pressure point on the limb. Method A two-dimensional link segment model that simulates relative motion between the limb and orthosis was developed. The OKC was systematically misaligned in the anterior-posterior (A-P), proximal-distal (P-D) directions, and their combination to simulate orthosis/thigh strap sliding and identify pressure points on the thigh. Simulations were performed for stand-to-sit activity and walking with a knee-ankle-foot orthosis. Results It was found that OKC misalignment causes increased A-P and P-D relative motions with an increase in misalignment distance for the stand-to-sit activity. The A-P and P-D relative motions are of greater concern for activities involving increased knee flexion such as sitting, squatting, and kneeling as compared with walking with an orthosis. Although the A-P and P-D relative motions during walking are of small magnitude, they occur with reversals in the direction and are repetitive in nature, which may cause skin problems and discomfort due to recurring pressure points. Conclusions The model provides a means to study the consequences of misalignment and insights for orthosis modification for improved comfort. A software simulation tool based on the presented model can serve as an educational and training tool in prosthetics and orthotics courses for creating awareness about the importance of proper alignment of orthotic knee joints. Study of misalignments of this nature will also guide fabrication and fitting of lower-limb orthoses/exoskeletons.