The aging population is a global issue, and physical deterioration and frailty in elderly people has become a socio-economic problem in many countries
By Tiasha Parial, pursuing Electronics and Computer Engineering (spl in AI and ML) – 1st Year, Christ University
Introduction
The ageing population is a global issue, and physical deterioration and frailty in elderly people has become a socio-economic problem in many countries. The frailty of elderly people is reflected by reduced daily physical activities such as walking less frequently because of significantly reduced muscle mass and strength. In the worst instances, their muscles could further deteriorate, and they may become bedridden or immobilized, which may accelerate the deterioration of the neuromusculoskeletal systems and their interactions.
In addition to age-related pathologies, the number of patients experiencing mobility impairment caused by spinal cord injury (SCI) is also increasing because of accidents and diseases. Spinal cord injury predominantly occurs in people under the age of 30 years; therefore, the financial burden imposed on family and society is long-term and high. Patients who have a complete SCI lose motor and sensory functions in their lower limbs. In addition, they are at increased risk for several secondary medical consequences of paralysis such as osteoporosis, muscle atrophy, obesity, coronary heart disease, diabetes, insulin resistance, impaired bowel and/or bladder function, and pressure ulcers. In addition, patients who have various diseases and injuries such as cerebral paralysis and orthopedic injuries have a dysfunction in the lower extremities. Impaired mobility would significantly reduce life expectancy, and thus rehabilitation training is needed to help these patients recover and regain mobility. Therefore, it is necessary and impactful to develop assistive devices that utilize state-of-the-art technologies to help disabled people regain the ability to stand, walk and lead a normal life.
Apart from the demands in health care, the applications of robotic assistive devices for human strength augmentation are also in great need. Legs can adapt to a wide range of extreme terrains, and therefore legged locomotion is a desired method of transportation in these circumstances. Therefore, a leg exoskeleton can free people from much of the labor and burden of many types of manual work, lessen the likelihood of injury, and improve the efficiency of work.
An exoskeleton is a wearable bionic device that is equipped with powerful actuators at human joints and integrates human intelligence and robot power. With a built-in multi-sensor system, an exoskeleton can acquire the wearer’s motion intentions and accordingly assist the wearer’s motion. It can apply external force/torque to the wearer’s limbs under control and hence provide user-initiated mobility. The exoskeleton enhances the strength of the wearer’s joints. For example, an exoskeleton allows people with mobility disorders to regain the ability to stand and to walk over the ground, upstairs, and downstairs. Compared to traditional physical therapy, exoskeleton assistive rehabilitation has the advantages of reducing the work of therapists, allowing intensive and repetitive training, and it is more convenient to quantitatively assess the recovery level by measuring force and movement patterns. In other applications, it can also help an able-bodied person carry heavy loads. Therefore, with the help of an exoskeleton, wearers can achieve a high level of performance.
Universities, research institutes, and industrial companies have been actively performing research in this field, especially in recent years. Several exoskeleton systems have been developed and tested. Based on the part of the human body the exoskeleton supports, they can be classified as upper extremity exoskeletons, lower extremity exoskeletons (LEEs), full-body exoskeletons, and specific joint support exoskeletons.
Exoskeletons And Bone Health
Sixty percent of individuals with SCI suffer from osteopenia or osteoporosis; a progressive disease that leads to bone loss, especially in the distal femur and proximal tibia. Bone remodeling and demineralization is a continuous process, and it is a function of both osteoblastic and osteoclastic activities. The pattern of bone loss in persons with SCI differs from other clinical populations and it is commonly referred to as neurogenic osteoporosis. Bone loss occurs sublesionally at a rapid rate and approaches 1% of bone mineral density per week. Most bone loss occurs within the first 12 to 24 months after SCI and reaches steady state within 3-8 years post-injury. Furthermore, persons with SCI are likely to experience lower extremity fractures that may require close to several months to one year to re-initiate weight bearing using a standing frame or any other assistive devices. The high susceptibility of fracture in these regions may lead to other health consequences following immobilization similar to joint contractures and pressure injuries. Imaging techniques are now available to provide clinicians with insights regarding bone health after SCI. These techniques include X-rays, dual-energy X-ray absorptiometry (DXA), quantitative computed tomography (CT), magnetic resonance imaging (MRI). The first two techniques provide two-dimensional assessment of bone health, and the latter ones provide 3-dimensional volumetric assessment of bone architecture.
Exoskeletons And Physical Activity
Physical inactivity is a key feature following SCI, which is likely to lead to a sedentary lifestyle and increased sitting time. Prolonged sitting time has been shown to be an independent risk factor for cardiovascular disease, cancer as well as a factor for increasing all-cause mortality. A very important point that needs to be considered is low metabolic cost during exoskeleton training. Cardio-respiratory fitness is used as a key feature to determine overall health and inverse relationships were noted between VO2 max and cardiovascular disorders, insulin resistance and type 2 diabetes mellitus. It is unclear whether exoskeleton locomotion may induce this moderate intensity training, but it can definitely decrease sitting time and improve parameters of physical activity as demonstrated by increasing the number of steps, duration and distance of walking.
Exoskeletons provide bodily passive movement of the lower extremity without muscle contraction. This is likely to be accompanied with low oxygen uptake and energy expenditure during exoskeleton ambulation. Therefore, incorporating functional electrical stimulation (FES) in conjunction with exoskeleton training may be an effective strategy to offset this problem by initiating muscle contraction and increasing energy expenditure. Currently, hybrid exoskeleton brands may offer this feature; however, studies are currently underway to prove the effectiveness of this combination in persons with SCI. The combination of FES and robotic control is a challenging issue, due to the non-linear behavior of muscle under-stimulation and the lack of developments in the field of hybrid control. The hybrid system may overcome electromechanical timing delays and muscle fatigue as well as balance muscular and robotic actuation during walking.
Conclusion
Exoskeletons may improve several physiologic and psycho-somatic outcomes. Moreover, it is time to establish round table discussions including individuals with SCI (consumers), government and health policymakers, researchers and rehabilitation specialists to develop rigorous plans for the future of exoskeletons. As our knowledge and experience increase, more individuals with SCI should become eligible to gain the benefits of this promising technology.