1.1. Increasing Demands for Rehabilitation Robotic Devices
After the invention of MIT-Manus, the first robotic device for rehabilitation in 1992 [1
], over the last decade, the application of robotic technologies to rehabilitation has progressed from conception to reality. However, in South Korea, robotics-based rehabilitation has emerged only very recently. Across countries, there are some common factors that make robot-assisted therapy acceptable in medical settings, such as demographic factors, financial situations, and healthcare service issues.
The first basic factor is the increase in the number of the elderly requiring rehabilitation treatment and the resulting financial burden. The global population is aging, and especially South Korea’s population is aging at the fastest pace [2
]. Koreans aged 65 and older accounted for 14.3 percent of the total domestic population of approximately 50 million [3
]. This sharp increase in the elderly population has increased the demand for rehabilitative medical treatment, which is conventionally human resource intensive [4
] and thus costly. Moreover, there are service quality issues. There are very few physiotherapists available [5
]. Among the advanced countries, the percentage of physiotherapists for every 100 people in South Korea is 0.54, lower than 0.62 of the US and 0.89 of Europe [6
]; this is also a critical impediment for providing equitable healthcare services by service providers. In addition, conventional manual therapy is significantly affected by the experience of therapists, which makes it difficult to fulfil the requirements of high-intensity and repetitive training [7
]; therefore, effective treatment cannot be guaranteed [8
]. Utilizing robots in rehabilitation medicine is expected not only to release physicians from the heavy burden of training sessions but also to help patients precisely, quantitatively, and scientifically perform training exercises [9
]. Hence, demographic changes, costs incurred by patients, and service quality are the main parameters accelerating the development of rehabilitation robotic devices comprising some automatic systems, which allow several types of users from multiple dynamic settings, such as hospitals, wherein emergency situations occur, to utilize these devices to aid in their everyday activities.
Considering this high demand for robotic systems in rehabilitation treatment, the global rehabilitation robot market is expected to grow from $
40 million USD in 2014, at a compound annual growth Rate (CAGR) of 86.1 percent (24.27%), to $
1.8 billion USD by 2020 [10
]. In comparison, the domestic market in South Korea was worth $
7.6 million in 2014 but is projected to grow to $
65.2 million USD, increasing at a CAGR of 43.1 percent, by 2020 [11
]. Despite these promising growth prospects, there is some skepticism regarding the use of rehabilitation robots. Though MIT-Manus for upper limbs, Lokomat for lower limbs, and others claim to be successful in the global market, there are limited commercially available devices due to various reasons such as complexity of usage and difficulties in reproducing prototypes, lack of clinical trials showing evidence of their effectiveness and acceptance of the system in clinical practice, or price- and time-related issues [12
]. Similarly, although the South Korean government designated the robotics industry as a strategic sector in 2003 to foster growth and has strengthened investment and policy supports, the rehabilitation robotics market is still at its initial stage [13
Owing to difficulties in compiling statistical data at such an early stage, to analyze the rehabilitation robotics industry and market, it is worth referring to associated fields like the medical device industry and robotics industry of South Korea. As of 2014, the technical standard of rehabilitation medical devices in South Korea is 77.0 percent of and is 3.1 years behind the most advanced countries like the US and European countries [14
]. The medical device market of South Korea mainly comprises small- and medium-sized enterprises (SMEs), which account for 75.8 percent and 19.5 percent of the market, respectively [15
]. On the other hand, despite the high utilization of robots in industry and with the industrial robot market of South Korea ranked among the top five in the world [16
], the robot industry of South Korea is mostly composed of SMEs (92%) as well [17
]. These facts indicate that the rehabilitation robot industry of South Korea needs consistent support financially and through favorable policies to develop the competitive edge required to establish itself in the global market.
Because of the practical needs of society and the healthcare industry, rehabilitation robotics has become an attractive research field that has drawn considerable attention in the last decade [7
]; however, research progress in this field remains slow. In the past decade, most studies have focused on demonstrating the therapeutic effectiveness, efficiency, or advantages of robot-assisted therapy rather than conventional labor-intensive training procedures; therefore, research in this field should focus on overcoming these challenges to make robotics more user-friendly [1
] and create better interaction between robots and their diverse users [18
]. These unmet needs emphasize the importance of using a human-centered approach for developing rehabilitation robots. Nevertheless, the continuous advancements in rehabilitation robotics like other everyday devices have caused people to think that these devices are technology-driven products [19
] while ignoring the fact that these devices are to be used by a person.
To provide various users with a better experience when utilizing robotic devices, it is important to understand the factors influencing the perceptions of users regarding these devices; it is necessary to make them realize that these devices are usable from the pre-use to the post-use stage. Hence, to boost the development of rehabilitation robotic devices with enhanced usability, this paper mainly focuses on assessing the factors influencing usability on the basis of a usability questionnaire on robotic devices and then comparing the ratings provided by possible users for the factors influencing the usability of these devices.
1.2. Usability and Users of Medical Devices
In product development, user-centered approaches engaging users, and assessing and fulfilling their needs are used and these approaches have proved their worth [20
]. Likewise, in developing medical devices, user involvement has become a touchstone for determining the success or failure of a device [21
]. It is because no one but the users themselves can better judge and identify the barriers in using these devices; further, sharing their experience presents a valid rationale to identify possible risks [22
]. A more crucial point is that misunderstanding or not considering the needs of users in developing a consumer product causes under-utilization or rejection of the product [23
]; however, in medical devices, it raises the possibilities of errors leading to preventable patient injuries and more severe incidents in some cases [21
]. In other words, the occurrence of the errors indicates failure in understanding the usage contexts of the device and presuming situations where errors are likely to occur rather than actually analyzing the error possibilities; thus, the device is not in line with the mental models of users or the thought processes of users about how the device works in the real world.
Who is the user of medical devices including rehabilitation robots and who should be concerned during a development process? In the real world, some devices are operated only by clinicians, and some are operated by trained caregivers. As the diversity of medical devices widens, their users, having traditionally been regarded as just healthcare professionals and patients [26
], can also further diversify. In practice, users of medical devices range from well-trained people, such as medical doctors or nurses, to untrained people, such as laypersons or patients [28
]. These facts indicate that the users are heterogeneous with different points of view.
Through analyzing research on medical devices with user involvement, a medical device user can be defined as anyone who uses a medical device for treatment and/or for taking care of oneself or someone else; users necessarily fall into either the primary or secondary class based on the usage purpose; they could be using the devices for therapeutic purposes or for testing, calibration, and research [31
]. In addition, under these user classes, there are the various divisions of user groups and types depending on why the device is used, where the device is used, what stage the device is in its lifecycle, and what type of device is used.
This flexible user definition with several subclasses seems inevitable owing to two explicit trends in the healthcare industry. One is the increased use of devices by laypersons [32
] who, as a group, have higher diversity and thus should be included in any user testing [33
]. The other is the involvement of diverse users [34
], because user engagement is extremely important at each stage of the development process. These trends explain the necessity of having flexible definitions for medical device users and such definitions and classifications help integrate and understand the perspectives of diverse users by analyzing the different opinions they have on using medical devices.
1.3. Usability Assessment of Medical Devices by SMEs
The International Electro-Technical Commission (IEC) requires that medical device manufacturers implement a usability engineering process to analyze, specify, design, verify, and validate the usability of their equipment [35
]. In addition, the US Food and Drug Administration (FDA) requires proof of human factors/usability procedures in the development or (re)design of the medical devices for sale in the US [32
]. In the medical device industry, usability is no longer a luxury. Though the requirements of the IEC and FDA do not provide specific questionnaires immediately applicable to individual usability tests, these requirements specified help in raising awareness on the usability of medical devices in the industry.
However, when considering the medical device industry of South Korea, predominantly comprising SMEs, the requirements of agencies/regulatory bodies for examining and demonstrating the user-centered design of devices places an enormous burden on the industry. This has caused the SMEs of South Korea to adopt discount research techniques. From a practical perspective, usability tests of medical devices frequently involve moderately large sets of users ranging from 50 to 150 participants [36
]; however, the medical device enterprises of South Korea conduct usability tests of medical devices with approximately 20 people referring to the best practices of the industry [37
]. Such a small number of participants appears to be the reason for situations where there are doubts concerning the validity of the test results and user diversity. Usability practitioners familiar with handy research techniques [38
] may find that these techniques are not sufficient to address human safety requirements [36
], which is one of the main issues associated with medical devices. Medical device development during the last decade has placed increased importance on user issues related to device design, human errors, and patient safety [19
]. These factors necessitate the importance of utilizing referential tools universally and immediately for usability tests of various medical devices, which in turn can help reduce the burden of SMEs.
In many cases, usability research is characterized as a highly qualitative approach, but questionnaires are often utilized to identify remaining problems and evaluate success or failure in achieving the target usability values [42
]. Though there are well-known quantitative approaches—such as standardized questionnaires to evaluate usability including the Questionnaire for User Interface Satisfaction (QUIS), Software Usability Measurement Inventory (SUMI), Computer System Usability Questionnaire (CSUQ), and System Usability Scale (SUS) [32
]—these evaluation methods appear insufficient for medical devices because the methods mainly focus on assessing two-dimensional screens in computer systems. Table 1
summarizes these assessment tools.
Despite the absence of standardized questionnaires to evaluate the usability of medical devices, relatively less effort has apparently been made to establish a tool for evaluating rehabilitation devices. This is evident from the small number of studies regarding usability questionnaires in the healthcare area. Let us consider journal articles recently published between 2014 and 2019 (as of 30 August) in English and Korean from PubMed in the US and Research Information Sharing Service (RISS) of South Korea, respectively. When searched following a scoping review approach using the keywords “usability,” “questionnaire,” and “design,” combined with “medical device,” a total of 38 and eight studies were found, respectively. Out of the 38 studies listed on PubMed in English, 14 focused on screen-based equipment like mobile phones or information systems, 12 on small personal equipment like pen injectors and inhalation devices, 11 on intangible services, and one on orthodontic appliances for the upper limbs. Further, among the eight studies from the RISS, four studies were on screen-based devices, two focused on small personal equipment, one on various device comparisons, and another on service evaluation. Thus, considering this scarcity of studies about usability questionnaire development regarding medical devices for lower limbs, it is worth trying to establish a questionnaire for evaluating the usability of these devices.