A low cost instrumented glove for extended monitoring and functional hand assessment
Introduction
Rehabilitation researchers would like to quantify finger posture in order to understand joint motion during activities of daily living in individuals with movement disorders. Knowledge of how individuals use their hands and fingers as they interact with their home and community environments is critical in effectively planning and evaluating rehabilitation therapy and treatments for upper limb movement disorders. Evaluation of function directly in these environments would provide more realistic information than data collected in the clinic. For example, collection of hand posture data while individuals perform everyday activities such as eating, dressing, and manipulating objects would provide a much clearer picture of true hand usage, which may differ from the functional potential that is traditionally assessed in a clinical setting with ordinal scales such as the Functional Independence Measure or Modified Ashworth Scale (Bohannon and Smith, 1987).
While precise measurements of various aspects of finger motor control can be made in the laboratory (Darling et al., 1994, Lang and Schieber, 2004, Li et al., 2003), it is not clear how well these measurements correspond with utility in everyday life. The ability to monitor hand usage for extended periods of time in more natural environments could yield valuable information about the efficacy of various interventions.
Assessment of hand function typically encompassess several measurements such as range of motion (ROM), strength and ability to perform functional tasks. Evaluation of ROM has traditionally been a manual test in which flexion and extension are measured one joint at a time using a goniometer. While this provides useful information on passive ROM, it is impossible to evaluate ROM during the performance of functional tasks without special devices. Active ROM and functional ROM have been proposed as functional measures for a variety of evaluations including metacarpophalangeal (MCP) joint motion following joint replacement, prosthesis performance (Fowler and Nicol, 2001, Hume et al., 1990, Mallon et al., 1991) and surgical efficacy. However, it has not been established which method is the most appropriate to measure ROM to assess functional capacity (Hume et al., 1990, Mallon et al., 1991).
Beyond simple range of motion, detailed information about specific hand movements can be used to augment traditional methods in assessing function for rehabilitation, workplace overuse and usability issues, and compliance with physical therapy or telerehabilitation (Dipietro et al., 2003). In many of these cases, long-term monitoring of hand use has been proposed (Fowler and Nicol, 2001). However, no guidelines exist for minimum sampling rates, signal resolution and accuracy values, or sensor configurations appropriate for home use to provide useful information at a reasonable price.
Gloves containing sensors to measure flexion and extension have been proposed for semi-automated goniometery in order to address the shortcomings of passive measures and to explore functional activities (Dipietro et al., 2003, Rand and Nicol, 1993, Williams et al., 2000). Instrumented gloves or individual sensors can measure dynamic values of hand and finger posture in real time and store these data for post-processing and analysis. For example, commercial gloves include the DataGlove family (Fifth Dimension Technologies (5DT), Irvine, CA), Cyberglove (Immersion Corporation, San Jose, CA), and the Humanglove™ (Humanware S.R.L., Pisa, Italy). Various non-commercial devices have also been reported (Rand and Nicol, 1993, Karlsson et al., 1998, Zurbrügg, 2003, Jurgens and Patterson, 1997, Hofmann and Henz, 1995, Asada and Mascaro, 1999, Williams et al., 2000). Traditionally, these gloves have been directly cabled to a data collection computer and have restricted the wearer's movements. However, some companies now offer a wireless connection between the glove and a nearby data collection computer, allowing the wearer to move freely within the room. Both 5DT and Immersion have released wireless versions of their gloves, which use Bluetooth® technology to transmit data to nearby computers. These wireless options can be expensive and do not give the wearer freedom to move about the home and commuity settings while data is being collected.
A second drawback of existing instrumented gloves is that most may be difficult or impossible to don by individuals with significantly reduced range of motion in the hand and fingers secondary to brain injury or other trauma, as the glove must fit snugly enough to keep the sensors properly located over the joint of interest. In studies with quadriplegia, Castro and Cliquet found that gloves used to measure object manipulation had to be customized for each individual to ensure optimal sensor position and glove sizing (Castro and Cliquet, 1997). Both Wise and Dipietro found the commercial gloves used in their repeatability analyses fit poorly on healthy female subjects due to smaller hand size (Dipietro et al., 2003, Wise et al., 1990). Research studies reporting the use of commercial measurement gloves in the brain injured population report that individuals tested had relatively high levels of hand function and were physically able to don the glove. In the two studies reporting use of the Cyberglove with individuals with brain injury, all individuals had sufficient passive ROM to don the glove (>65° finger and 43° thumb ROM) (Merians et al., 2002) or functional capacity to hold a pen with precision grip (Lang and Schieber, 2003). Details on other devices and their applicability to this application appear elsewhere (Simone and Kamper, 2005).
Existing measurement methods (i.e., gloves) are not the optimal solution for assessing functional capacity over time and in the community for the broad range of hand function disorders observed in the clinic or rehabilitation facility. The Shadow Monitor was developed to allow unobtrusive measurements of finger postures across all ability levels in this underserved population (Simone and Kamper, 2005). Rather than encase the hand and fingers entirely and thereby exclude some individuals who cannot wear a glove-like device, it was designed to be worn on the back of the hand and shadow the wearer's hand activities. The device wirelessly records continuous streams of finger posture as individuals perform daily activities, providing a wealth of new information for the evaluation and treatment of movement disorders in the hand and fingers. Short- or long-term testing can be performed without tethering to a computer. Data can be stored locally on the device if transmission to a computer is not possible. Currently up to eight sensors can be used; while attachment anywhere on the hand is possible, we attached sensors to the dorsum, leaving the palm free of obstruction. The system is significantly less expensive than currently available wireless systems.
The purpose of this research was to evaluate the device for use in clinical populations. Repeatability and reliability of sensor measurements, wireless transmission rate failure, and user acceptability were assessed.
Section snippets
Components
The Shadow Monitor is a lightweight measurement device designed to measure finger joint flexion automatically. The wearable system includes a signal conditioning/wireless transmitter box and a disposable sensor glove containing commercially available sensors. The electronics box can be mounted at different places on the arm based on activity and comfort of the subject. Mounting on either the forearm (Fig. 1) or upper arm is possible (Fig. 2a).
The most important requirements for the Shadow
Repeatability testing
Following calibration, raw data block files were processed. A single data block file contains 10 cycles for each of the 5 MCP joints; a sample data block from Test C (flat hand) is shown in Fig. 6. In Fig. 7, a sample data block for one joint from Test A (grip mold) is shown with pushbutton markers that are used to automatically extract joint angles for each position. Ten such data block files were processed to produce 10 averaged values for each joint, as shown in Fig. 8. The decay present
Discussion
The Shadow Monitor was evaluated for repeatability, reliability, wireless transmission, user acceptance, and battery life.
While both Immersion Corporation and 5DT have released commercial wireless gloves with a forearm-mounted form factor similar to the Shadow Monitor, battery life was much longer for the Shadow Monitor. The Shadow Monitor transmitted continuously for nearly 60 h, significantly outperforming both the Data Glove Ultra Wireless (reported in company literature at more than 8 h) and
Conclusion
The Shadow Monitor provides several advantages over other proposed and evaluated systems and over manual goniometry. First, the Shadow Monitor accommodates all hand sizes. Despite varying hand sizes and the inclusion of both genders, we did not need to segregate results based on hand size, which was done for both the DataGlove and Humanglove in order to account for gloves that did not fit snugly on female subjects (Dipietro et al., 2003, Wise et al., 1990).
A second advantage is the unique
Acknowledgements
This material was based on work supported by the Foundation of University of Medicine and Dentistry of New Jersey (#29-05), the Henry H. Kessler Foundation, the Coleman Foundation, and the National Institutes of Health (NIH 1 R24 HD050 821-01). The authors wish to thank Brad Galego for his contribution.
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