Occurrence and Type of Adverse Events During the Use of Stationary Gait Robots—A Systematic Literature Review

Abstract

Robot-assisted gait training (RAGT) devices are used in rehabilitation to improve patients' walking function. While there are some reports on the adverse events (AEs) and associated risks in overground exoskeletons, the risks of stationary gait trainers cannot be accurately assessed. We therefore aimed to collect information on AEs occurring during the use of stationary gait robots and identify associated risks, as well as gaps and needs, for safe use of these devices. We searched both bibliographic and full-text literature databases for peer-reviewed articles describing the outcomes of stationary RAGT and specifically mentioning AEs. We then compiled information on the occurrence and types of AEs and on the quality of AE reporting. Based on this, we analyzed the risks of RAGT in stationary gait robots. We included 50 studies involving 985 subjects and found reports of AEs in 18 of those studies. Many of the AE reports were incomplete or did not include sufficient detail on different aspects, such as severity or patient characteristics, which hinders the precise counts of AE-related information. Over 169 device-related AEs experienced by between 79 and 124 patients were reported. Soft tissue-related AEs occurred most frequently and were mostly reported in end-effector-type devices. Musculoskeletal AEs had the second highest prevalence and occurred mainly in exoskeleton-type devices. We further identified physiological AEs including blood pressure changes that occurred in both exoskeleton-type and end-effector-type devices. Training in stationary gait robots can cause injuries or discomfort to the skin, underlying tissue, and musculoskeletal system, as well as unwanted blood pressure changes. The underlying risks for the most prevalent injury types include excessive pressure and shear at the interface between robot and human (cuffs/harness), as well as increased moments and forces applied to the musculoskeletal system likely caused by misalignments (between joint axes of robot and human). There is a need for more structured and complete recording and dissemination of AEs related to robotic gait training to increase knowledge on risks. With this information, appropriate mitigation strategies can and should be developed and implemented in RAGT devices to increase their safety.

Safety Assessment of Rehabilitation Robots: A Review Identifying Safety Skills and Current Knowledge Gaps

“…As this principle of applying forces through contact points is the same for all rehabilitation robots, the following sections refer to not only stationary gait trainers, but rehabilitation robotics in general. Although the hazards identified through our recent review (Bessler et al, 2020) are based on incidents with stationary lower limb robots, comparable hazards have been reported in upper limb and mobile devices (Rocon et al, 2008;He et al, 2017;Schwartz et al, 2018;van Herpen et al, 2019). Although the interface mechanics between human and robot are often comparable, there are some obvious differences, such as lower weight bearing in upper limb rehabilitation robots and different location and surface area of device-skin interface.…”

“…Due to the increased number and surface area of contact points in exoskeleton-type devices opposed to end-effector-type devices, one might expect that the risk of sustaining such an injury is higher when using exoskeleton-type devices. However, the abovementioned systematic literature review (Bessler et al, 2020) showed that was not the case in stationary gait trainers (see also Figure 1). Many events of discomfort or injuries to soft tissue which were reported in end-effector-type device studies were attributed to the safety harness worn by the patient and the amount of body-weight support seemed to have an influence on the risk of soft tissue-related adverse events caused by the harness in exoskeleton-type devices but not in end-effector-type devices.…”

“…Safety of rehabilitation robot use in clinical trials, including the monitoring and reporting of adverse events (Mehrholz et al, 2017;Mehrholz et al, 2018), is one important aspect. However, this has been covered elsewhere (Bessler et al, 2020) and will therefore not be addressed in this article. This article is instead focusing on guidance for validating mechanical safety of rehabilitation robots in the development phase, as required for the risk management process (International Organization for Standardization, 2010; International Organization for Standardization, 2019a).…”

“…The protocols are testing procedures for safety validation and not to be confused with protocols used to evaluate safety during robot use, e.g., by monitoring adverse events in clinical trials (Nef et al, 2007;Borggraefe et al, 2010;Rodgers et al, 2019). While addressing comfort and safety during use of rehabilitation robots is important (Bessler et al, 2020), we are aiming to develop procedures for validating mechanical safety in the development phase, usually without a human in the loop. Ultimately, this aims to advance safety of a rehabilitation robot as much as possible before testing it clinically with (impaired) persons, potentially reducing the number or severity of adverse events occurring.…”

“…In a recent systematic literature review (Bessler et al, 2020), we collected information on occurrence and type of adverse events reported in connection with training in stationary robotic gait trainers. We counted approximately 17 adverse events per 100 subjects trained in a stationary robotic gait trainer.…”