Haptics offer information about touch, while force feedback is the ability of receptors in our organs to perceive varying levels of force, which results in action by the musculoskeletal system. Physiological force feedback, for example, is essential when walking or running. Touch sensors on the soles of the feet along with the force feedback that the muscles, tendons, and tissues perceive and dictate the pattern in which the musculoskeletal system will move. Thus, it is clear that in haptic mechanics, both physiologically and mechanically, force feedback is assumed to be an important part of the control system and compliance.
When we look at the current use of external haptic devices that use touch and force feedback, this is typically accomplished through vibration (applications are widespread in the gaming community, surgical devices, motion stimulation, etc.)1 2 The data collected from these applications provides positive evidence that the technology is engaging for the user and that there is variability and flexibility in its application in a range of environments3.
This article proposes the use of haptic mechanics and force feedback interfaces in the medical industry with particular reference to rehabilitation following injury.
One of the most common forms of neural injury is stroke, which is a leading cause of long-term disability. Stroke poses a significant burden to the patient, their families and society alike4. Standard therapy through a rehabilitation program is typically offered to enhance function of the sufferer following a stroke, however, it remains that 55-75% of stroke survivors continue to experience functional limitations5.
In a stroke model, haptic sensors and force feedback mechanics have been well-studied in their role in bilateral rehabilitation, where hemiparesis is a common result of the resulting brain injury. The addition of mechanics and their aim to promote rehabilitation of the injured side is prominent in stroke rehabilitation literature6.
The use of haptics and force feedback devices are employed in the program as a specific means to target the plasticity of the brain. Neuroplasticity describes the ability of the nervous system to adapt and change to various responses within its environment. It has been described as the ability of the nervous system to be able to reorganize its structure, function, and connections, depending on either intrinsic or extrinsic stimuli.
Neuroplasticity remains an active area of research, particularly when it comes to injury and rehabilitation. A greater understanding of the topic has led to the ability to produce more established and targeted interventions which has provided a major advantage in the area of rehabilitation and brain injury7.
There is a significant body of research to support the use of force feedback mechanics for this process.
Brewer et al., 2008, suggested many individuals with stroke or traumatic brain injury have a tendency to present with reduced ability to use an affected upper limb, most typically due to learned non-use. During therapy, the individual may not strive for certain goals due to difficulty, which has a negative effect on their progress through their rehabilitation program and thus poorer outcomes following rehabilitation, which includes progressive deterioration of motor function 9.
This phenomenon of learned non-use during therapy is not uncommon in the literature, and it is becoming increasingly popular to include the use of haptics, robotics, and virtual reality into the rehabilitation programs of such individuals, which has shown significant and beneficial improvements that may counteract the phenomenon and improve the motor gains in stroke patients 10.
The last point above is reiterated by Lv et al., 2016. This time, the research suggests that costly devices take a long time to develop. When there are design defects, the cost and time to completion significantly increases. Evaluation strategies with these costly robotics may only be accurately gathered once the strategy has been implemented for some length of time.
Additionally, the use of these applications are informed using static images and oral instructions which may make compliance for the patient more difficult.
With the development of virtual reality devices using haptics and force feedback mechanics, these issues may be overcome. Virtual reality environments are not only quicker to develop, they provide a faster degree of evaluation and the application and training purposes are more effective15. A Boy Wearing a VR Headset While a Therapist Examines His Arm
Forcefeedback and VR Used in a Rehabilitation Exercise
Accurate and easily accessible quantitative data can be collected and recorded, which allows for in-training analysis. This information allows the clinician to gain insight into the training program during the therapy session which allows for real-time adjustments to be made and errors quickly corrected 17.
Biofeedback has been presented as being simple, yet effective in the practice of rehabilitation of stroke patients. Afzal et al., 2015, present a patient model of stroke victims using kinesthetic haptic feedback for improvement of balance. External haptic devices are used to detect body tilt and orientation where a stroke patient’s internal sensory response to these physiological changes may be absent or inadequate due to brain injury.
Programs that involve task-oriented exercises using external sensory input have a significant impact on the standing balance of stroke victims which appears to improve the ability of the injured brain to be retrained in sensorimotor function. This results in improvement in post-training postural stability that is retained even after the program has ended 18 19. These are only a few examples of the areas of the application of force feedback mechanics in stroke rehabilitation. The application extends to another common area of research of neuroplasticity: traumatic brain injury.