Role of Robotic Technology in Rehabilitation of Patients with Traumatic Spinal Cord Injury and its Future Challenges

THE BURDEN OF DISABILITY AND THE NEED FOR INNOVATIVE TECHNOLOGY

Every year, 250,000-500,000 people suffer from spinal cord injury (SCI) globally.^[1] Majority of these cases are due to preventable causes such as road traffic accidents, falls, and assault. Up to 90% of these cases are due to traumatic causes, although the proportion of nontraumatic SCI appears to be growing.^[2]

In India, management and rehabilitation of patients with SCI lag far behind developed countries even when the economy is growing at a fast pace. A comprehensive multidisciplinary management and technology-driven innovative rehabilitation approach is the need of the hour to reintegrate patients with SCI into the mainstream of society.

ROLE OF ROBOTIC TECHNOLOGY

Structured physical rehabilitation favors the functional recovery following traumatic SCI. However, following the functional recovery, only 20% of patients fully resume their social life and occupation.^[3] Hence, we need effective and patient-customized rehabilitative procedures to maximize the functional outcome to improve their quality of life and functional independence.

The advantage of robotics-based rehabilitation when compared to conventional therapy is that it helps consistent training of the prescribed intensity for extended periods of time. Robotic devices offer flexibility and can use data from the sensors and correlate feedback of the user’s performance to provide appropriate movements during rehabilitation training.

MOTOR LEARNING AND REHABILITATION

A group of muscles can be recruited by motor learning to aid in functional recovery following SCI.^[3] The guiding principle used in occupational and physical therapy is to achieve not only motor control and learning but also the acquisition of more accurate and normalized motor patterns. This principle can be made use of in motor learning and further rehabilitative procedures.

Robot-aided rehabilitation strategies aim for optimal control by practicing fairly consistent patterns of coordination and reinforcing tasks. Robotic devices can be precisely programmed to provide such training of various magnitudes and speed along with visual and proprioceptive feedback, which can be manipulated and enhanced using computer-based robotics, which is critical to adapt to new movement conditions.

The first robotic device for rehabilitation was built in 1992 (MIT-Manus),^[3] offering two degrees of freedom to the shoulder and elbow. A randomized controlled trial comparing robotic-assisted gait training to conventional gait training found that robot-trained subjects attained a normal gait pattern compared to conventional gait training.^[3]

Several challenges, including cost, accessibility, safety, efficacy, and use friendliness, need to be addressed. Significant research is still going on to investigate the development of low-cost robotic devices for rehabilitation.

TYPES OF ROBOTIC DEVICES FOR REHABILITATION

Most of the robotic devices used in clinical settings today are active or interactive but may also act in a passive manner. Based on the interface of the device with the user, the devices may be classified as end-effector devices or exoskeletal devices.

End-effector robotic devices

End-effector devices connect to the user through a manipulandum that is held in the hand or foot.^[3] The manipulandum is connected to a robotic arm, which provides the force supplied to the user and contains the sensors that measure performance. Since the forces and measurements occur at a single interface, this type of system can easily be adapted to users of various body sizes without major modifications to the system. End-effector systems are popular for rehabilitation of the upper limb and for gait training.

Limitations

Since the interaction with the robot is only at a single interface, the movements at each joint cannot be independently adjusted.

The MIT-Manus^© is an end-effector type of robot for the upper limb.^[3] Sensory-motor training using this device uses simple video games, where the input is provided through the motion of the manipulandum. The goal of training is to move a point on the screen through interaction with the manipulandum, enabling the user to draw shapes or move along a path. If the user is unable to accomplish the task, assistive force is provided by the robot through the manipulandum [Figure 1].^[3]

Figure 1: Courtesy: Krebs HI, Volpe BT, Williams D, Celestino J, Charles SK, Lynch D, et al. Robot-aided neurorehabilitation: A robot for wrist rehabilitation. IEEE Transactions on Neural Systems and Rehabilitation Engineering 2007;15:327-35

End-effector robots are also used to improve lower limb function, which is typically easier to train compared to upper limb function. The Haptic Walker^© is an end-effector type robot that is able to simulate walking and stair climbing [Figure 2].^[4] Force and torque sensors allow for an interactive control strategy while enabling data collection to gauge the user’s progress and walking performance.^[4] The G-EO-System^© is a similar end-effector robot for gait training. Such gait training robots allow for repetitive training with minimal effort from a physical therapist without increased risk of falling.^[4]

Figure 2: Courtesy: Taherifar A, Hadian MR, Mousavi M, Abbas Rassaf A, Ghiasi F. “LOKOIRAN – A novel robot for rehabilitation of spinal cord injury and stroke patients.” 2013 First RSI/ISM ICRoM 2013;218-23. RSI: Robotics Society of Iran, ISM: Iranian Society of Mechatronics, ICRoM: International Conference on Robotics and Mechatronics

Exoskeletal devices

In contrast to the end-effector robots, the exoskeleton-type robots act directly upon specific joints. They are difficult to design and construct as they must have the design of the limb adjustable to accommodate users of different anthropomorphic dimensions and need an attachment to the limb at multiple points.^[5] The forces at each joint can be adjusted using motors, but the joints are typically connected using rigid links attached to the arm.

Current designs of exoskeletons for the upper limb use rigid links that add inertia to the segments of the human arm, making it 4–6 times heavier, which invariably requires users to use compensatory nonphysiological muscle strategies during movement. Approaches to reduce the inertia of the exoskeleton are to place the motors away from the joints and drive the joints using cables and pulleys.^[5]

The cable-driven upper arm exoskeleton, CAREX^©, is a novel robot which suspends the arm using a robot-controlled cable system, making it ten times lighter [Figure 3].^[5]

Figure 3: Courtesy: Wu Q, Wang X, Chen B, Wu H. Patient-active control of a powered exoskeleton targeting upper limb rehabilitation training. Frontiers in neurology. 2018;9:817. DOI: 10.3389/fneur. 2018.00817. PMID: 30364274; PMCID: PMC6193099

For the lower limb, the Ankle Bot^© is a two-degree-of-freedom exoskeleton robot that directly actuates the ankle and is capable of detecting deficiencies in gait and actively applying corrective forces to train a paretic ankle and improve both balance and walking [Figure 4].^[6]

Figure 4: Courtesy: Tijjani I, Kumar S, Boukheddimi M. A survey on design and control of lower extremity exoskeletons for bipedal walking. Applied Sciences. 2022;12 (5):2395. https://doi.org/10.3390/app12052395

CHALLENGES TO ADOPTION AND ACCESSIBILITY TO ROBOT-ASSISTED REHABILITATION

Huge cost

Although robotics-based rehabilitation and telerehabilitation have both been widely demonstrated to be effective, they are not yet part of routine treatment in most centers. This is due to the fact that commercially available rehabilitation robots are very costly. Considerable effort is now geared toward the development and adoption of low-cost devices.

Lack of availability and lack of motivation

Supplementing rehabilitation exercises with additional motivational elements could indirectly improve the effectiveness of rehabilitation interventions through increased compliance. Including gaming consoles has been shown to increase motivation and enjoyment during exercise, and interactive computer play may be an effective means of engagement in children.

Lack of engaging interfaces and feedback

Most early robotic devices lacked engaging interfaces. More recent efforts have begun to include interactivity and virtual reality elements in an effort to challenge patients and provide additional motivation.

Java therapy is an early example of the use of a low-cost gaming device for rehabilitation of the arm and hand in an effort to increase accessibility to rehabilitation in home settings.^[5] It consists of a force feedback joystick connected to a home computer with custom software. The system has been found to be feasible to provide therapeutic treatment over the Internet and enable a therapist to assess progress.^[5]

Availability of structured gaming virtual environment

Games designed primarily for entertainment may be too fast-paced for sensorimotor-impaired individuals. Serious games developed not purely for entertainment but specifically for rehabilitation hold more promise in this regard. Structured gaming that uses available games but in a step-by-step guided manner may be one solution to using existing gaming consoles.^[5]

Catering to all population

The older population presenting with a neurologic disability may be more receptive to games that challenge their intellect in contrast to the typical action and reflex video games. Rather than presenting gaming or competitive elements, participants should be presented with educational content and engage the participants cognitively and simultaneously enhance visuomotor dexterity.^[6]

Lack of adaptability to the home environment

Rehabilitative exercises can be more easily, effectively, and routinely executed from the comfort of the home when compared to clinical environments. However, substantial progress remains to be made to make robot-assisted home-based telerehabilitation an affordable reality.

CONCLUSIONS

The use of robotic technology has the potential to transform rehabilitation from specialized centers to a technology-driven, remotely supervised, and widely accessible option that can be done at home through telerehabilitation. The cost-effective development of robotic rehabilitation is essential. New developments such as affordable lightweight devices, incorporation of motivational elements such as gaming, virtual reality, and user-friendly access to technology are underway to empower therapists and patients. Robotic rehabilitation will require further development of telerehabilitation services to efficiently rehabilitate individuals in their own homes.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.